Greenbatteries – Solar Products, Battery Chargers, Synergy Digital, Rechargeable Batteries

Greenbatteries – Rechargeable batteries, battery chargers, battery testers, adapters, covers and cases.

  • FREE SHIPPING on orders over $70
  • TRUSTED STORE 30 Day Money Back Guarantee
  • SECURE SHOPPING buy with confidence

Greenbatteries are dedicated to providing helpful information regarding the use of rechargeable batteries and chargers, to increase their use and to contribute in a small way to a more sustainable future for our planet.

Batteries are an integral part of our lives in the 21st century and regardless of whether you use single use batteries or rechargeable batteries it is essential that you use them effectively so that you get the most out of your battery investment.

Whether you are looking for rechargeable batteries out of concern for the environment, for the superior power of rechargeable batteries, or for the money you will save, is the best site to help you make an environmentally friendly rechargeable battery purchase.


We have several different types of li-ion battery chargers available.
One is the style that you see above with the silver charger base and the black battery insert.
The second one is a travel li-ion battery charger that has a foldable plug and a CLA for portablility. The third has the ability to charge two li-ion batteries at the same time using two battery adapter plates.
You can mix and match the plates and you can even get a charger plate for NiMH AA and AAA batteries.
Also there are several photo lithium battery chargers for CR123, CR-V3, CR2, and 2CR5 type lithium ion cells. These li-ion battery chargers are perfect for all your rechargeable lithium ion digital camera batteries.

Solar Products, Battery Chargers, Synergy Digital, Rechargeable Batteries – Greenbatteries Online Shop

NiMH Batteries AA, AAA, C, D & 9V
Digital Camera Batteries Lithium ion, NiMH
Rechargeable Nickel Zinc NiZN 1.6V
Rechargeable Sealed Lead Acid Batteries SLA, AGM
Alkaline & Lithium Batteries AA, AAA, and CR 123 A type
Alkaline Batteries
Lithium Batteries AA, AAA, and CR 123 A type

Solar Products Shop

  • Power Film Solar
  • Solar Battery Chargers
  • Sun Oven
  • Solar Cooking

Battery Chargers Shop

  • NiMH & NiCD Battery Chargers
  • Digital Camera Battery Chargers – Lithium Ion
  • Battery Chargers By Brand Name
  • Solar Battery Charger
  • Interchangeable Battery Plates
  • Battery Accessories site

Greenbatteries - Solar Products, Battery Chargers, Synergy Digital, Rechargeable Batteries

Name : green batteries;
Seller : Greenbatteries;

Country : USA;
Sity : Reno, Nevada;
postalCode : 89511;
Street : 16157 Galena Meadows Drive;
Telephone : 1-800-790-7866;

BRANDS greenbatteries Battery

Belkin | Delkin | Duracell | Eneloop | Energizer | Enersys | Go Green | GoGreen | Gold Peak | Greenbatteries | Imedion | iPower | LaCrosse | Maha | Minwa | Powerex | Powerfilm | Powergenix | Powerpax | Sanyo.


iPower 520mAh 9V Lithium Polymer Pro Rechargeable Battery.
Energizer e2 Lithium, Size AAA, 4 pack non-rechargeable, single use batteries.
Energizer e2 Lithium, Size AA, 8 pack – non-rechargeable, single use batteries.
CR123A Lithium Photo / Flashlight Primary Batteries – 10 pack.


Which of our NiMH (Nickel Metal Hydride) & NiCD (Nickel Cadmium) battery chargers would be the best battery charger for your specific requirements? – a smart battery charger, a solar battery charger, a universal battery charger (to charge AA, AAA, C, D, and 9 volt NiMH and NiCD batteries), one with battery conditioning or battery analyzer features? We have many to choose from in our store.
TurboCharger 4000 Smart Battery Charger and Conditioner,
iPower 9v Lithium/NiMH/NiCD Battery Charger,
Maha 10 cell smart charger for 9 volt NiMH – charge 7.2V, 8.4V 9.6V,
Maha NiMH 9 Volt Smart & Fast Charger,
Universal Smart Battery Charger and Conditioner,
Maha 8 Cell Smart Charger/Conditioner AA AAA C D NiMH NiCD Batteries,
Maha MH-C9000 WizardOne AA and AAA Smart Charger – Analyzer,
Maha 8 cell Smart Charger and Conditioner AA, AAA, NiMH & NiCD batteries,
Maha MH-C401FS-DCW Smart Charger with Car Adapter,
GP Powerbank Torch,
Smart charger with LCD display and four separate charge channels,
Energizer e2 15 Minute Charger for AA & AAA batteries & 4 – 2200mAh AA batteries,
8-Cell AA/AAA NiMH Smart Battery Charger with discharge/conditioning and DC adapter,
Basic AA & AAA NiMH battery charger,
Battery Charger 2-4-6-8,
10-Cell AA/AAA Smart Battery Charger and Conditioner,
Universal Battery Charger,
“Speedy” Charger for AAA – AA – 9V NiMH Batteries,
9V NiCD & NiMH Single Battery Charger,
Energizer Family Charger – new unit with LCD battery charge readout.

Digital Camera Battery Chargers – Lithium Ion Digital Camera Battery Chargers – Green Batteries

Battery Charger base and battery plate for Pentax EI-D-Li1 Type Lithium Ion Batteries.
Digital Camera Charger for Kodak KLIC-7002 type li-ion batteries.
Digital Camera Charger for Kodak KLIC-7001 type li-ion batteries.
Digital Camera Charger for Olympus LI-30B type li-ion batteries.
Digital Camera Travel Charger for Sony FE-1 type li-ion batteries.
Digital Camera Travel Charger for Nikon ENEL-20 type Battery.
Digital Camera Travel Charger for Samsung BP-1030 type Battery.
Digital Camera Travel Charger for GoPro AHDBT-001 type Battery.
Digital Camera Travel Charger for Minolta LB-4 type li-ion batteries.
Digital Camera Charger for Olympus BLM-1 type li-ion batteries.
Battery Charger for Fuji NP-80 and NP-100 Type Lithium-ion Batteries.
Digital Camera Charger for Olympus L1-10B type li-ion batteries.
Battery Charger for Canon BP-511 , BP-511A , BP-512 , BP-514 batteries.
Digital Camera Travel Charger for Fuji NP-30 type li-ion batteries.
Digital Camera Travel Charger for Nikon EN-EL2 type li-ion batteries.


TurboCharger 4000 Smart Battery Charger and Conditioner
Maha 10 cell smart charger for 9 volt NiMH – charge 7.2V, 8.4V 9.6V
Maha NiMH 9 Volt Smart & Fast Charger
Universal Smart Battery Charger and Conditioner
Maha 8 Cell Smart Charger/Conditioner AA AAA C D NiMH NiCD Batteries
Maha MH-C9000 WizardOne AA and AAA Smart Charger – Analyzer
Maha 8 cell Smart Charger and Conditioner AA, AAA, NiMH & NiCD batteries
Maha MH-C401FS-DCW Smart Charger with Car Adapter
Energizer e2 slider charger for AA & AAA Rechargeable batteries
GP Powerbank Torch
Energizer slider charger for AA & AAA Rechargeable NiMH batteries with 4 – 2300mAh AA NiMH batteries
Energizer Energi to Go Instant Cell Phone Charger plus 2 Lithium AA Batteries and 3 Motorola Connectors
GP Powerbank Universal Charger
Energizer charger for AA & AAA Rechargeable batteries with car and home adapter & 4 AA batteries
Energizer AA or AAA NiMH Value Charger




This interchangeable battery plate will convert your TurboCharger LX charger so you can charge numerous different models of Li-ion batteries. Need an extra 110 volt plug, 100-220V AC Adapter , the cord can be purchased separately, just in case your new puppy chews. Do you travel and want to charge your camera battery in the car, an extra 12volt car cord is what you require. If you own more than one type of camera, these interchangeable battery plates are for you.
Battery Plate to Fit Olympus 200483, LI-30C type batteries
Interchangeable Battery Charger Plate for the BP-511 li-ion type battery
Changeable Battery Plate for Fuji NP-100, NP-80 Kodak KLIC-3000, Toshiba PDR-BT1, Ricoh DB-20, DB-20L, Epson EU-85, JVC more type batteries
Changeable Battery Plate for Kyocera BP-780S
Changeable Battery Plate for Minolta NP-400, Pentax D-LI50, Samsung SLB-1674, Sigma BP-21 type batteries
Changeable Battery Plate for Panasonic CGA-S, CGR-S, DMW-BM, Leica BP-DC5-E type batteries
Changeable Battery Plate for Panasonic CGA-S003, CGA-S003A/1B, VW-VBA05
Changeable Battery Charger Plate for Minolta NP-500, Konica NP-600, DR-LB4 type batteries
Changeable Battery Plate for Konica Minolta NP-700, Pentax D-LI72, Sanyo DB-L30, Samsung SLB-0637 type batteries


Our exclusive battery wallets come in several types and are designed to be a AA battery holder but can fit many other sizes too. The battery contact covers are specifically designed to be used with the specific li-ion battery in each battery holders title and description and they snap on securely so that your charged battery is safer to carry in your pocket, pack or purse. The plastic battery cases, aka battery storage boxes, are great for AA and AAA batteries and come in several colors of plastic – each battery holder has its own design features too. The clear green cases will clip together to make carrying even easier. Our battery adapters are designed to convert AA and AAA batteries to size C and D batteries. Kits come in a package of two adapter sets and they are easy to use. These converters can work with NiMH or alkaline batteries.
Leather Battery Wallet with Belt Clip
Plastic battery cases for AA and AAA batteries – Clear Green
Nylon Battery Wallet – a battery case and digital memory card holder.
Powerpax Battery Caddy for 4 – D batteries
Powerpax Battery Caddy for – 4-CR123 batteries
Powerpax Battery Caddy for 4 – C batteries
Battery Adapter – Converter AA to D – set of 4
Powerpax AA Battery Caddy
Battery Adapter – Converter AA to C – set of 4
Powerpax Battery Caddy for 6 AAA batteries
Powerpax Battery Caddy Holds AA, AAA, 9V Batteries
Powerpax 9v Battery Caddy


We carry simple low cost battery checkers for AAA, AA, C, D, and 9 volt batteries and full featured ZTS Multibattery Testers that can test dozens of different kinds of batteries. Battery adapters that allow you to always have the right size battery available for use. We also have a few battery chargers that have great battery analyzer features – The BC-700 and the BC-9009 from LaCross Technology and the MHC-9000 from Maha.
ZTS Lead Acid Multi Battery Tester and Accessory Kit
Battery tester for AA and AAA battery – clear plastic
Mini Multi Battery Tester – 9v NiMH version
Mini Multi Battery Tester – 3v Lithium version
ZTS Multibattery Tester
Low Cost Battery Checker


We offer battery accessories like the AC adapter battery charger pictured above that is designed to replace the AC adapter that ships with the TurboCharger LX Smart Battery Charger and the Powercharger II+. The adapter has a standard US style two-prong plug. It may require a plug adapter to fit the local AC outlet of different countries.
Input: AC 100-240V 50-60 hz 50W
Output: DC 12 V 1000 mA
Polarity: Negative outside, positive inside-5MM diameter-10MM length
The Worldwide Plug Adapter Set allows you to plug devices with US two prong type plugs into the AC outlets found in other countries. This battery accessory is ideal for use with multi-voltage battery charger devices like the TurboCharger 4000 Smart Battery Charger. This four plug set covers 95% of the world including UK and Ireland, Europe, and Australia.
*Please note: These are not voltage converters, they simply adapt the plug. Your battery charger or other device must be able to accept the local voltage. **We also offer the Mini Travel Charger Kit for lithium-ion rechargeable batteries for your travel needs.
Our 12V DC car cord allows the POWERcharger II, or the Ultralast CR123A charger to operate in cars or other vehicles that have a cigarette lighter outlet. These charger battery accessories can also be used as a replacement for the POWERcharger II 12 volt adapter since that battery charger currently has one included.
With our 12 volt socket multiplier, you can plug two battery accessories into any standard 12 volt automotive outlet. Simply insert the 2 in 1 adapter into your cigarette lighter and plug the battery accessory of your choice into the ports on the rear side of the unit.
Our mini tripod with tilting panhead is so useful and compact you will want to take it everywhere. Especially designed for use with digital cameras and mini camcorders. Great for use with your self timer, so you can get in the shot too!

Non-slip rubber feet.
Measures 4.5″ tall when set up.
Folded measurement is 8″ long.
Easily fits into any camera or battery accessories bag!


Powerfilm Accessory RA-1 Male Cigarette Lighter Adapter for PowerFilm® Rollable Solar Panel
Powerfilm R-28 Rollable Solar Panel – 28 watt
Powerfilm R-21 Rollable Solar Panel – 21 watt
Powerfilm R-7 Rollable Solar Panel – 7 watt
Powerfilm R-14 Rollable Solar Panel – 14 watt
Powerfilm F16-1800 Foldable Solar Panel – approx. 30 watt
Powerfilm AK-2 Adventure Kit
Powerfilm AK-1 Assurance Kit
Powerfilm Accessory RA-2 Female Cigarette Lighter Adapter
Powerfilm F15-600 Foldable Solar Panel – approx. 9.25 watts
Powerfilm Accessory RA-6 Daisy Chain Accessory
Powerfilm F15-300N Foldable Solar Panel – approx. 5 watts
Powerfilm F16-3600 Foldable Solar Panel – approx. 60 watt
Powerfilm F16-1200 Foldable Solar Panel – approx. 20 watt
Powerfilm Accessory RA-9 Charge controller
Powerfilm Accessory RA-11, 15 ft. Extension Cord with O-ring
Powerfilm Accessory RA-8, 15 foot extension cord w/ Alligator Clips
Powerfilm Accessory RA-7 15 foot extension cord




Sun Oven


What is the difference between Lithium batteries and Lithium Ion batteries?

There are several important differences. The practical difference between Lithium batteries and Lithium-ion (Li-ion) batteries is that most Lithium batteries are not rechargeable but Li-ion batteries are rechargeable. From a chemical standpoint Lithium batteries use lithium in its pure metallic form. Li-ion batteries use lithium compounds which are much more stable than the elemental lithium used in lithium batteries. A lithium battery should never be recharged while lithium-ion batteries are designed to be recharged hundreds of times.

What are the advantages of Lithium Ion batteries compared to other rechargeable batteries?

Lithium-ion batteries have several advantages:

They have a higher energy density than most other types of rechargeables. This means that for their size or weight they can store more energy than other rechargeable batteries. They also operate at higher voltages than other rechargeables, typically about 3.7 volts for lithium-ion vs. 1.2 volts for NiMH or NiCd. This means a single cell can often be used rather than multiple NiMH or NiCd cells.

Lithium-ion batteries also have a lower self discharge rate than other types of rechargeable batteries. This means that once they are charged they will retain their charge for a longer time than other types of rechargeable batteries. NiMH and NiCd batteries can lose anywhere from 1-5% of their charge per day, (depending on the storage temperature) even if they are not installed in a device. Lithium-ion batteries will retain most of their charge even after months of storage.

So in summary; lithium-ion batteries can be smaller or lighter, have a higher voltage and hold a charge much longer than other types of batteries.

What are the disadvantages of Lithium Ion batteries compared with other rechargeable batteries?

Lithium-ion batteries are more expensive than similar capacity NiMH or NiCd batteries. This is because they are much more complex to manufacture. Li-ion batteries actually include special circuitry to protect the battery from damage due to overcharging or undercharging. They are also more expensive because they are manufactured in much smaller numbers than NiMH or NiCd batteries. Li-ion batteries are becoming less expensive and over time we should see their price decrease significantly.

Lithium ion batteries are not available in standard cells sizes (AA, C and D) like NiMH and NiCd batteries.

UPDATE: I just discovered an overseas manufacturer that sells down regulated li-ion cells in several standard cell configurations, AA, AAA, etc. that outputs 1.5 VOLT S – whaatttt?? How long have they been on the market? Are they reliable? Are they safe? Kentli is their name and I need to get some samples and test the heck out of them ASAP. Lithium ion is considered a “volatile” cell chemistry so I am a bit skeptical but finally a manufacturer has gone and ventured into that territory. This could be both disruptive and awesome. More to come. 😉

Lithium-ion batteries also require sophisticated chargers that can carefully monitor the charge process. And because of their different shapes and sizes each type of Li-ion battery requires a charger designed to accommodate its particular size. This means lithium ion battery chargers are more expensive and more difficult to find than NiMH and NiCd battery chargers.

Are Lithium Ion batteries available in standard sizes like AA , C or D cell size?

No, Lithium-ion batteries are not available in standard sizes. We believe this is because it would be too easy for users to inadvertently put them in a charger not designed for Lithium-ion batteries creating a potentially dangerous situation. (If an alkaline battery is put into the wrong charger it might leak or even burst, but a lithium-ion battery put into a NiCd or NiMH charger not designed for lithium-ion, might ignite. Also, because Li-ion batteries operate at much higher voltage (typically 3.7V per cell) than the 1.2 to 1.5V of most cell batteries, designing a 1.5V lithium-ion cell would be expensive.

What is the difference between “name brand” (Canon, Nikon, Fuji, etc.) Lithium Ion batteries and the other types?

Like prescription drugs there is often very little difference between name brand lithium-ion batteries and generic lithium-ion batteries. Camera makers often make very little from the sale of the camera itself, but have high profit margins for the accessories, like batteries and flashes. Not all third party batteries are the same quality as the original battery, but many (including those which we sell) are virtually identical.

What is the best way to store Lithium Ion batteries?

Lithium-ion batteries can hold a charge for many months. It is best to store a lithium-ion battery with a partial or full charge. Occasionally, a lithium-ion battery with a very low charge is stored for a long period of time (many months) and its voltage slowly drops to below the level at which its built in safety mechanism allows it to be charged again. If the battery is going to be stored for several months it’s a good idea to take it out and recharge it after a few months. Better yet would be to actually use the battery every few months and then leave it partially or fully charged.

If my camera (or other electronic device) uses alkaline batteries can I use Lithium Ion batteries?

The answer depends on the particular camera or device. But in many cases you can not. Because the size, shape and voltage of alkaline and lithium ion batteries are different they are not interchangeable. However, some camera makers have designed some of their cameras in a way that allows the camera to work with either AA size batteries or CRV3 type lithium batteries. If your camera or other device can use different types (chemistries) of batteries the User’s Manual should mention it. Also check here to see if your camera can use the rechargeable CRV3 batteries that we carry. Important – There are several different kinds of rechargeable CRV3 lithium ion batteries now available under various brands and they cannot use each others chargers – they are designed as a set and have different charging requirements. This is one area, unlike NiCD and NiMH batteries that you need to get one brand of rechargeable battery, and its matching charger, and stick with it.

Another alternative would be to use an external battery pack of some sort. These are sometimes available with Lithium-ion batteries.

If my camera (or other electronic device) uses NiMH or NiCd batteries can I use Lithium Ion batteries?

Normally you can not switch between a NiMH or NiCd battery and a lithium ion battery in a digital camera. There are some devices specifically designed to use either type of battery, cell phones are the most common example. If you can use either type of battery, it should say so in the User’s Manual.

How should I dispose of Lithium Ion batteries?

Lithium ion batteries, like all rechargeable batteries are recyclable and should be recycled. They should never be incinerated since they might explode. Most places that sell rechargeable batteries will also accept them back for recycling.

NIMH BATTERY FAQ. Which are better, NiCd batteries or NiMH batteries?

For most electronic devices it is better to use NiMH batteries than NiCd batteries. NiCd batteries use Cadmium, a highly toxic heavy metal, that can damage the environment if not disposed of properly. (They should be recycled not discarded). NiMH batteries usually have a higher capacity than NiCd batteries of the same size. Some people argue that NiCd batteries deliver faster discharge rates than NiMH batteries. While this may be true under certain circumstances, the difference is not relevant when considering power sources for electronic devices like digital cameras or portable music players. (If you are choosing a battery to drive a high torque power screwdriver, then NiCds can outperform NiMH). NiMH batteries require more sophisticated chargers than those typically used for NiCd batteries. But smart chargers designed especially for NiMH batteries are now readily available.

Is it normal for my digital camera to use so many alkaline batteries?

Unfortunately, it is. Digital cameras use alkaline batteries at a shockingly fast rate. (For an explanation why, see the following question). If you are using lots of alkaline batteries for your electronic devices you’ll probably want to switch to rechargeable NiMH batteries ASAP. Not only will the NiMH batteries power a digital camera (or most other electronic devices) much longer than alkaline batteries will, but they are much less expensive to use.

Why do my alkaline batteries run down so quickly when used in a digital camera (or other electronic device)?

Alkaline batteries were not designed to meet the very high power demands of today’s electronic devices. Alkaline batteries have a high rated capacity, but they can only deliver their full capacity if the power is used slowly. (See alkaline drain chart). Electronic devices such as digital cameras place a high power drain on batteries, so it is much better to use rechargeable NiMH or NiCd batteries for these type of devices. Lithium ion rechargeable camera batteries also work well in high drain applications like digital cameras but can be more expensive.

Do Ultra or Advanced Formula alkaline batteries last any longer than standard alkaline batteries?

Yes, for high drain applications Duracell Ultra and Energizer Advanced Formula batteries do last longer than standard alkalines. Unfortunately, they only last about 30% longer. So instead of lasting for say 15-25 images they might last for 20-40. That’s a little better but it’s still pretty poor, especially considering that these new style alkalines cost as much as $1.50 each. Rechargeable NIMH or NiCds are the better choice for high drain applications. They last much longer on a single charge and don’t have to be discarded after a single use.

What about rechargeable or renewable alkaline batteries?

Rechargeable alkalines work well for some uses but, they are not a good alternative for use in digital cameras. They typically have an even lower capacity than standard alkaline batteries. This means that if a standard alkaline only lasts for a few exposures, a rechargeable alkaline will last for even fewer!

Can NiMH batteries be substituted for alkaline batteries even though they are only 1.2 volts?

Yes, for most high drain electronic applications NiMH batteries are ideal substitutes and you needn’t worry about the apparent voltage differences. Even though alkaline batteries are rated at a nominal 1.5 volts, they only deliver 1.5 volts when they are fully charged. As they begin to discharge the voltage of alkaline batteries continuously drops. In fact, over the course of their discharge, alkaline batteries actually average about 1.2 volts. That’s very close to the 1.2 volts of a NiMH battery. The main difference is that an alkaline battery starts at 1.5 volts and gradually drops to less than 1.0 volts. NiMH batteries stay at about 1.2 volts for most of their discharge cycle.

There are a couple of cases where their actual voltage difference may be important to you. In the case of a device like a radio, where a higher voltage can mean a stronger signal, a fresh alkaline battery may be more desirable – but more expensive – than a rechargeable NiMH battery. This is also true for a flashlight, which will be brighter with the initial higher voltage of alkaline cells. This minor difference may not be important to you and is probably offset by the much lower cost of operating NiMH batteries. And keep in mind that the alkaline battery only has a higher voltage when it is fully charged. Once it gets to 50% capacity or less, it will be delivering a lower voltage than a NiMH battery.

The one time when the voltage difference of the two is important would be in the case of a device that checks the voltage of a battery to estimate the amount of charge left on the battery. Because the voltage of an alkaline battery drops at a very predictable rate it’s possible to estimate the amount of capacity left in an alkaline battery based solely on its voltage. (1.5 volts – fully charged, 1.25 volts – 50% charged, 1.0 volts – almost fully discharged). But a NiMH (or NiCd) battery stays at about 1.2 volts until it is nearly completely discharged. This makes it almost impossible to know the amount of capacity left based on its voltage alone. When a device that’s using NiMH batteries indicates the battery is low, it’s time to change the batteries now!

Do NiCd batteries really have a memory effect?

Answering this question is a sure way to start a flame war on the internet. The simple answer is: Technically speaking NiCd batteries do not have a memory effect. However, they do suffer from a voltage depletion or voltage depression phenomenon that most people call the memory effect. So practically speaking, NiCd batteries do suffer from a memory effect, even if it is not technically correct to call it that. There is a lot of disagreement in the battery industry over what actually causes voltage depression. The phenomenon itself is very real. If a NiCd battery is repeatedly charged after it has only been partially discharged it will develop a lower voltage and a lower capacity. Fortunately, this effect is reversible by conditioning NiCds. Conditioning is simply fully discharging the battery (down to about 1.0 V per cell) after charging it. If a full discharge followed by a charge cycle is done several times, a battery suffering from voltage depletion (voltage depression, memory effect, or whatever you would like to call it) should be restored back to its normal voltage and capacity.

If you use NiCd batteries you should be aware that most of the problems experienced by NiCd battery users are not due to a “memory effect” but are due to overcharging or improper storage. Overcharging is usually caused by poorly designed first generation battery chargers. These chargers continue to deliver current to the batteries even after the batteries are full charged. “5- hour” and “8-hour” timer type chargers can damage NiCd or NiMH batteries if they are frequently used to charge batteries that are only partially discharged.

The other common cause of damage to NiCd and NiMH batteries is leaving them in a device like a flashlight left “ON” after the battery has run down. Electronic devices normally switch themselves off once the battery is discharged. But other devices like flashlights, cassette players, and many toys, will continue to put a small load (drain) on a battery even after the battery is run down. Eventually (after a few weeks) this drain on a discharged battery will cause the polarity of the battery to reverse (the plus end actually becomes minus and vice versa). Once this happens the battery will not take a charge again. Battery makers recommend that rechargeable batteries be removed from any devices that will not be used for several weeks or longer.

The big difference between voltage depletion, the so called “memory effect” and damage caused by overcharging or improper storage, is that reduced capacity due to overcharging is not reversible.

Do NiMH batteries have memory effect?

Technically, NiMH batteries do not have a “memory effect”, but strictly speaking neither do NiCds. However NiMH batteries can experience voltage depletion, also called voltage depression, similar to that of NiCd batteries, but the effect is normally less noticeable. To completely eliminate the possibility of NiMH batteries suffering any voltage depletion effect manufacturers recommend an occasional, complete discharge of NiMH batteries followed by a full recharge. NiMH batteries can also be damaged by overcharge and improper storage (see the NiCd section immediately above this one). Most users of NiMH batteries don’t have to be concerned with this voltage depletion effect. But if you use a device say a flashlight, radio, or digital camera for only a short time every day and then charge the batteries every night, you will need to let the NiMH (or NiCd) batteries run down occasionally.

How many times can a rechargeable battery be recharged?

I normally answer that question by simply saying “hundreds”. The reason I can’t be more precise is because this is a more complex question to answer than it might seem. The number of times a battery can be recharged depends on how the battery is used. An analogy that is sometimes used is to compare a rechargeable battery to a loaf of bread. Suppose someone asked, how many slices can be cut from a loaf of unsliced bread? The answer, of course, depends on how thick or thin the bread is sliced. If the slices are very thin it can be cut into more slices. The same is true for recharging a battery. Every time a rechargeable battery goes through a charge and discharge cycle it loses a tiny bit of capacity.

If the battery is completely discharged before it is recharged, that takes a bigger “slice” of the battery’s capacity, if it is only partially discharged a before recharging, it uses up a smaller “slice”. A NiMH battery can be charged and discharged hundreds of times, but whether that means 200 times or 800 times has a lot to do with how big of a “slice” you take each time.

Does putting batteries in the freezer or refrigerator make them last longer?

It depends on which type of batteries and at what temperature you normally store them.

Alkaline batteries stored at “room temperature” will retain 90% of their power for years without refrigeration. Under normal circumstances, refrigerating or freezing alkaline batteries will extend their life by less than 5%. (see Battery Myths)

NiMH and Nicad batteries, start to lose power when stored for only a few days at room temperature. But they will retain a 90% charge for several months if you keep them in the freezer after they are fully charged. If you do decide to store your charged NiMH cells in the freezer or refrigerator, make sure you keep them in tightly sealed bags so they stay dry. And you should also let them return to room temperature before using them.

Does rapid charging reduce the life of batteries?

No. So long as it is done using a properly designed, smart charger, most NiMH batteries can be recharged in about an hour without any damage or reduction in their life. However, NiMH batteries must be rapid charged with a specifically designed NiMH battery charger. Chargers designed to charge NiCd batteries can overcharge NiMH batteries. Even a standard or slow NiCd charger can damage NiMH batteries.

What does mAh stand for?

mAh stands for milli Ampere hour or milli Amp hour. It is a measure of a battery’s energy storage capacity. If you think of a battery as a small fuel storage tank, which in a sense it is, mAh a measure of how much “fuel” the battery holds. (This is roughly comparable to using gallons to measure how much fuel a gas tank can hold. The more gallons of capacity, the more fuel the tank can hold.) With a battery the higher the mAh rating the more electrical energy it can store.

While it is useful to think of mAh as being the rough equivalent to gallons, the analogy is not a perfect one. Different types of batteries use different methods to measure mAh so comparing the mAh rating of one type of battery, say an alkaline battery to another say an NiMH battery, is not always meaningful. However, in general, the mAh rating of a battery is a quick way to compare the relative energy storing capacity of one battery to another battery of the same type.

Can I substitute a higher mAh battery for a lower one?

If the batteries are of the same type, i.e. both are NiMH or both are Lithium-ion, then you can use a higher capacity (i.e. higher mAh) battery instead of the lower one. The reverse is also true. Using a higher mAh rated battery will allow the device to run longer on a charge. So a camera should take more pictures and a music player can play more songs.

Keep in mind that it will take a little longer to charge a higher capacity battery. (Staying with the fuel tank analogy from above, it would also take longer to fill a 20 gallon gas tank than a 12 gallon tank).

What is the shelf life of a NiMH battery?

You probably mean to ask: What is the self discharge rate of a NiMH battery? The rate of self discharge for any battery depends on the temperature at which it’s stored. Stored at 70 degrees F (20 C) NiMH batteries will lose up to 40% of their charge within a month. If they are stored at a higher temperature, they will self discharge at an even higher rate. NiMH batteries stored at a lower temperature self discharge at a lower rate (Self discharge chart available soon).


brief overview of all the different types of AA and AAA batteries today: Alkaline, Rechargeable Alkaline, NiZN, NiMH, NiCD, and lithium batteries (rechargeable and non-rechargeable) that are available in today’s market.

AA and AAA batteries are probably the most common battery sizes for consumers today. The challenge is there are so many different kinds of AA and AAA batteries, nickel metal hydride batteries, lithium batteries, lithium ion batteries, alkaline batteries, each of them have their strengths and weaknesses for use in today’s modern electronic equipment.

What we will try to do it here is to explain the pros and cons of each different battery type and explain what the recommended ideal battery type for different applications might be so that you can make an informed decision about which batteries to use for all of your tools and toys.

First a bit of detail about each battery type and then a AA Battery Comparison Table to compare them to each other in an overview.

alkaline AA and AAA batteries – if you don’t use a lot of batteries and the devices that you do have are not gobbling up your alkalines – you can still use them, you can’t beat em for convenience and initial cost. However, if you use lots of them like many people do you are wasting money and you need to consider using rechargeable batteries.

rechargeable alkaline AA and AAA batteries – if you have devices that perform better with the 1.5 volts of an alkaline and are not high drain (high drain devices deplete alkaline batteries very quickly) then this battery chemistry will work well for you. You can also get them with chargers that can also charge NiMH batteries, so that is pretty convenient.

lithium AA and AAA batteries – if you need batteries that last for years or are fantastic in extreme temperatures, this is the ticket. Yeah, I know – they are not rechargeable but there are some applications that these are really the best batteries for the job. They do last several times longer than alkalines, up to seven so the ads go…

nickel metal hydride AA and AAA batteries – my personal favorite. Environmentally friendly rechargeable batteries! If you use your device a lot and over a short period of time – say days or weeks, the higher the mAh rating on your NiMH high capacity battery the longer it will last per charge (it will also take longer to charge though) Now available in a Ultra Low Self Discharge (ULSD) – also known as ready to use NiMH batteries – so you can buy them and they are ready to use! This is a better choice for general purpose use if you use devices that are not high drain (it is not high drain if it does not use up alkaline batteries fast) Or if you do not use it frequently.- e.g.- I have a Kodak digital camera and I like it OK but don’t use it a lot. I’ll take a few pictures and then leave it in a drawer for weeks and weeks. This is the perfect application for the ULSD type of NiMH batteries. The self discharge issue with NiMH batteries is probably their biggest weakness and this new type of battery addresses this very nicely. If you have not tried them you really need to get some…

NiZN – These are not new batteries per se but have been re-engineered to make them really an exciting alternative. They are 1.6 volts, designed for high drain devices and roughly equivalent to 2500 mAh NiMH in terms of usable energy. Very cool new patented manufacturing process by a San Diego company and they are now available on! Get some now and see for yourself.
nickel cadmium AA and AAA batteries – in some cases these batteries are still a good choice and for high temperature applications or some commercial applications these are actually better than NiMH. Not environmentally friendly though – bummer…

lithium ion AA and AAA batteries – this is really confusing because technically there is no such thing as rechargeable Li-ion 1.2 or 1.5 volt button top consumer batteries. However, there are AA size rechargeable Li-ion batteries. They are typically 3.6 or 3.7 volts and they require a dedicated charger, so really only the serious techies even know about them. FYI – we do not carry them.

crv3 batteries – this is a common lithium, lithium ion, and sometimes even NiMH AA battery equivalent that many manufacturers are trying to make available to replace two AA batteries and also have them be safe enough for the average consumer to use. They are approximately the size and shape of two AA batteries but they are connected. They are available in regular non-rechargeable lithium in most camera stores.

They are occasionally found in rechargeable NiMH type but most often found in the lithium ion rechargeable type and for the lithium ion type it is important to use a dedicated charger – do not mix and match these batteries in other manufacturers chargers – lithium ion battery technology still has some safety issues that are best not “tested” in your home or office. 😉


Ad – Battery reconditioning instructions for the do-it-yourself battery tech – save money, and learn how to recondition your own rechargeable batteries.

Rechargeable batteries have a lower capacity than disposable alkaline batteries.

This is really a huge challenge for all of us because you can see companies everywhere advertising their “battery fact” as rated capacity and what they are really doing is perpetuating the “battery myth” that disposable batteries have a greater actual or available capacity than rechargeable batteries.

The actual or available capacity for a battery is way more important to actual usage but is also more complex to determine, because it really depends on what you are using the batteries for. (For more detail see battery terms page – “actual capacity”.)

For most high drain electronic devices, like digital cameras, rechargeable batteries will continue to work much longer than alkaline batteries. In fact, in devices like digital cameras, NiMH batteries will run on a single charge for 3-4 times as long as they would on an alkaline battery. Look at this chart of a brand name alkaline battery and a high capacity NiMH battery both set up in a computerized battery analyzer and subjected to a high drain rate of 500 mA.
You can see that the NiMH battery lasts WAY longer than the poor old alkaline battery when subjected to this high discharge rate.

Heavy Duty, Super Heavy Duty, High Capacity, Quick Charger, Rapid Charger, Ultra, Long Life, etc.

Since there are no real industry standards, many terms used by battery manufacturers have become misleading marketing hype.

“Heavy Duty” batteries are often the least powerful batteries you can buy and some “quick chargers” can take as long as seven hours to recharge a set of batteries!

I believe these terms didn’t start out as misleading. For example the term Heavy Duty battery was used to refer to Zinc chloride batteries which had about 50% more capacity than traditional carbon zinc batteries. But that was 50 years ago! Calling zinc chloride batteries heavy duty became misleading once alkaline batteries with 300% more capacity than zinc chloride batteries became available.

A similar situation happened with battery chargers. Originally NiCd battery chargers took anywhere from 12-24 hours to recharge NiCd cells. Later, chargers that could recharge NiCd cells in half that time were introduced. Unfortunately, calling these chargers “quick chargers” was a real disservice to the rechargeable battery industry. Anyone that purchased NiCd cells and a “Quick charger” only to realize later that a quick charge took seven hours must have been very disappointed. I know I was.

The good news is that it’s now possible to buy a battery charger that can recharge batteries in less than two hours, and in some cases even as fast as one hour or less!!

Battery capacity ratings are meaningless when used to compare different types of batteries or to compare the capacity of batteries powering different types of devices.

This means that you may not be able to predict how long your electronic device will run just by looking at the capacity rating of a battery. For example AA alkaline batteries typically have a capacity rating of over 2,500 mAh and AA NiMH batteries have rated capacities of only 1,200 to 1,900 mAh. But when it comes to actually powering an electronic device like a digital camera, the NiMH batteries will often run the device for three or four times as long.

(for an explanation see Battery FAQ, Why do my alkaline batteries run out so fast?)

Unfortunately, even comparing the capacity ratings of similar types of batteries won’t always work because different manufacturers often measure battery capacity in slightly different ways.

Putting batteries in the freezer or refrigerator doesn’t necessarily prolong their life

Alkaline batteries stored at “room temperature” self discharge at a rate of less than two percent per year. So normally refrigerating or freezing them will only help maintain their charge by a tiny amount. Hardly worth the effort of chilling them. However, if alkaline batteries are stored at higher temperatures they will start to lose capacity much quicker. At 85 degrees F they only lose about 5% per year, but at 100 degrees they lose 25% per year. So if you live in a very hot climate or are storing your batteries in a very hot location, it may be worthwhile for you to store your alkaline batteries in a refrigerator instead.

NiMH and NiCd batteries self discharge at a MUCH faster rate than alkaline batteries. In fact, at “room temperature” (about 70 degrees F) NiMH and NiCD batteries will self discharge a few percent PER DAY. Storing them at lower temperatures will slow their self discharge rate dramatically. NiMH batteries stored at freezing will retain over 90% of their charge for full month. So it might make sense to store them in a freezer. If you do, it’s best to bring them back to room temperature before using them. Even if you don’t freeze your NiMH batteries after charging them, you should store them in a cool place to minimize their self discharge.

Quick charging NiMH batteries will reduce their life.

For practical purposes with batteries that are designed to be quick charged, for example, Sanyo, GP, Maha, Energizer, that is not true. It is important to use a battery charger that has been specifically designed to rapid charge NiMH cells. Actually there is a much greater likely hood of reducing the life of a NiMH battery by using an “overnight” charger than by using a smart fast charger. Overnight chargers rely on the fact that you will unplug them after a number of hours. If you forget to unplug them they can continue to charge the batteries longer than they should. Overcharging WILL reduce the life of batteries. From a strictly technical sense, a battery that is always slow charged will likely last a little longer than one that is always rapid charged. However, the difference is so small that it is not likely to be noticeable for most users.

A battery with a capacity of 2,800 mAh can deliver a current of 2,800 mA for an hour

Assigning capacities to batteries can be very tricky, that’s probably why you don’t see capacity ratings marked on most alkaline batteries. When powering high drain electronic devices like digital cameras, computer peripherals, or portable music players, an alkaline battery will only deliver a small fraction of its rated capacity. A NiMH or NiCd battery is likely to deliver much closer to its rated capacity when it’s powering high drain devices. This means that a NiMH battery with a rated capacity of 1800 mAh can take many more photos than an alkaline battery with a rated capacity of 2,800 mAh.

FREQUENTLY ASKED QUESTIONS ABOUT NIMH AND NICD BATTERY CHARGERS. What’s the difference between a rapid charger and a fast charger?

Both terms are essentially meaningless. There is no standard in the industry, so manufacturers can use the terms in different ways. One of the problems with terms like these is that the amount of time it takes to charge a battery is dependent on the capacity of the battery being charged. A charger that can charge a standard capacity AAA NiCD battery (180 mAh) in just one hour might take 8 hours to charge a high capacity NiMH (1500 mAh) battery. It’s best to ignore such terms and make a rough calculation of how fast a charger can charge batteries. (To do this you can use our Battery charge-time calculator.)

How long will it take a charger to charge batteries?

It’s pretty easy to estimate how long it will take. Simply divide the capacity of the battery by the charge rate of the charger, then increase the amount of time by about 20% to allow for a certain amount of inefficiency. As an example, a battery with a capacity of 1600 mAh will require about 4 hours to be fully charged by a charger with a charge rate of 500 mA. (1600 mAh/500 mA x120%). Incidentally, this example would apply to a standard AA NiMH battery and a typical “rapid charger”. Keep in mind that a battery that is only partially discharged will be recharged in less time.
If this seems too complicated, please use our Battery charge-time calculator.

Can a battery charger damage a battery (shorten its life or reduce its capacity)?

Yes. The most common cause of premature battery failure is overcharging. The type of chargers most likely to cause overcharging are the 5 or 8 hour so-called “rapid chargers”. The problem with these chargers is that they really don’t have a charge control mechanism. Most of them are simple designs which charge at their full charge rate for a fixed period of time, typically five or eight hours, and then shut off or switch to a lower “trickle” charge rate. If they are used properly, these chargers are fine. If they are used improperly they can shorten a battery’s useful life in a couple of ways.

First, suppose fully charged or partially charged batteries are put into the charger. The charger has no way to sense this, so it will give the batteries the full charge it was designed to deliver. It is not unusual to put partially charged batteries into a charger since it’s pretty easy to mix batteries up and inadvertently put fully charged batteries into a charger. Do this enough times with one of these battery chargers and the capacity of the battery will start to drop.

Another common situation is for the charge cycle to be interrupted part way through the charge. The charger is unplugged to see how warm the batteries feel or to use the electrical outlet for something else. Then the charger is plugged back in. Unfortunately, this will cause a complete charge cycle to start again, even if the previous charge cycle was almost complete.

The easiest way to avoid these scenarios is to use a smart charger, a charger with microprocessor control. A smart charger can determine when a battery is fully charged and then depending on its design, either shut off entirely or switch to trickle charge. Most of our chargers use microprocessor control. For specific information see our Battery charger comparison table.

What is trickle charge?

Theoretically a trickle charge is a charge rate that is high enough to keep a battery fully charged, but low enough to avoid overcharging. Maintenance charge is another way to describe trickle charge.
Determining the optimum trickle charge rate for a particular battery is a bit tricky to describe but is generally accepted to be around ten percent of the battery capacity – i. e. Sanyo 2500 mAh AA NiMH optimum trickle charge rate is at or below 250mA.
One of the reasons it is important for you to understand the optimum trickle charge rate for your charger and batteries is to compensate for the self discharge of NiCD and NiMH batteries.
Another reason is because overcharging a battery will definitely reduce its useful life.
Although most manufacturers do not recommend that you leave a battery in the charger for long periods of time, many people leave their batteries in the charger on trickle charge for days or weeks to keep their batteries “ready to use”.
If you know the rate of trickle charge that your charger puts out and it is around one tenth of the battery capacity or less, then you should be alright if you are just going to do this occasionally. Generally speaking, though you do not want to leave a battery charger plugged in unattended for long periods of time.

Is trickle charging harmful to batteries?

Many battery manufacturers do not recommend long term ( months at a time) trickle charging. If trickle charging is used then the charge rate should be very low or only intermittent. The best smart chargers will only send an occasional pulse charge to the battery once it is charged. They do not apply a continuous low rate of charge. Some battery resellers state that applying a continuous trickle charge of about 1/10th the battery’s capacity is not harmful. However, we have not seen any battery manufacturer condone the practice.

It is better to fully charge batteries and then store them fully charged in the freezer than to leave them on trickle charge for very extended periods of time.

Does rapid charging reduce the life of batteries?

Not significantly. So long as it is done using a properly designed smart charger, most NiMH batteries can be recharged in about an hour without any damage or significant reduction in their life. However, NiMH batteries must only be rapid charged with a charger specifically designed for charging NiMH batteries. Chargers designed to rapidly charge NiCd batteries can overcharge NiMH batteries. While it may be true that rapid charging NiMH batteries can reduce battery life by a small amount (probably less than 10%), this should be more than offset by the inconvenience of always slow charging batteries.

What’s the difference between a NiMH battery charger and a NiCd battery charger.

The biggest differences are in the charge rate (how fast the charger can charge batteries) and the charge control (how the charge determines when to stop the charge). Many of the inexpensive NiMH battery chargers are simply NiCd chargers that have been modified slightly. Typically a 5 hour NiCd charger has a switch that allows the charge time to be increased from five hours to eight hours. Thus a 5 hour NiCd charger becomes an 8 hour NiMh charger. As we mentioned above, we do not recommend this type of charger design. While a timer type charger is less expensive to manufacture than a smart charger, it can lead to overcharging and battery damage if batteries are frequently charged before they have been discharged (that is, the batteries are used for a short time and then fully charged again).

NiMH smart chargers have actually been designed to detect when a NiMH battery is fully charged and then shut off or go into a trickle charge mode. Because of the more complex circuitry, this type of charger costs more to make, but should lead to greater battery life. Some of these chargers only cost slightly more that the “dumb” chargers. We strongly recommend investing in a smart charger for your NiMH or NiCd batteries.

Can I use an older NiCd battery charger to charge NiMH batteries?

The answer to this question depends on the type of NiCd charger. Depending on the type of NiCd charger you have, the older NiCd charger may undercharge NiMH batteries (most likely), it may overcharge them (less likely), or it may charge NiMH batteries properly (but it’s not likely to do so automatically and could take a very long time). Let’s take a look at the three cases.

Many of the older NiCd chargers are the simple timed type charger which will charge batteries for a fixed amount of time and then shut off. Unfortunately, since NiCd batteries have a much lower capacity than NiMH batteries, the timer is likely to shut off long before the NiMH batteries are fully charged. This won’t harm the batteries, but the NiMH batteries won’t be fully charged since the timer will have stopped the charge cycle too soon.

Also common among older NiCd chargers are the so called “overnight” chargers which charge batteries at a low rate as long as the charger is plugged in. This type of charger can fully charge NiMH batteries, but it might take a very long time to do so. It’s possible that an old NiCd charger could take as long as 48 hours to fully charge new high capacity NiMH batteries! This type of charger is not likely to damage NiMH batteries unless the batteries are left in the charger for weeks at a time, but it may not be very convenient to use. If you have this type of charger you can get an idea of how long you’ll need to charge your batteries by using the calculator found above.

The final possibility is that the older NiCd charger is a rapid charger that will charge NiMH batteries but will not have the necessary circuitry to stop the charge cycle once the NiMH batteries are fully charged. If the NiCd charger is designed to charge batteries in less than two hours it may be this type. In this case the risk is that the older charger will overcharge NiMH batteries. This will be apparent if the batteries get very hot during the charge cycle. (It is normal for NiMH batteries to get warm as they become fully charged, especially in a rapid charger). If the NiMH batteries get too hot to handle and stay that way for more than 20 or 30 minutes, then the NiCd charger is most likely overcharging the NiMH batteries and may shorten their life. You would be most likely to encounter this type of charger if the charger was designed for rapid charging radio control (RC) vehicle batteries. We would recommend that you not use an NiCD rapid charger to charge NiMH batteries.

Which are better, NiCD or NiMH batteries?

This really depends on what you are going to use them for exactly. NiCD batteries are commonly used for power tools and in that capacity they are in many ways superior to NiMH batteries. For high drain digital devices where weight is of primary importance, NiMH batteries are the best choice. NiMH batteries are also considered an environmentally friendly battery chemistry. NiCD’s are toxic and recycling them is mandatory.

What is battery conditioning or exercising?

When you intentionally discharge a battery down to a certain minimum voltage and then recharge it this is known as battery conditioning or reconditioning . It is also sometimes referred to as battery exercise. This is particularly important to reduce what some call the memory effect experienced using NiCD batteries if you habitually do not fully discharge them each time you use them. For NiCD batteries this must be done periodically, approximately every 10 charge/discharge cycles or so, or the batteries will begin to lose capacity. For NiMH batteries conditioning is not really needed to reduce any memory effect because that is negligible in this type of battery. However, reconditioning is very convenient for both NiMH and NiCD batteries because brand new batteries are not charged when you receive them and they must be charged and discharged three to five times before they reach their full capacity. In addition, occasionally conditioning rechargeable batteries helps to ensure that they give you years or service and save you as much money as possible, before you recycle them and get new ones.

What is a charge channel or charge circuit?

Battery chargers have one or many charge channels aka charge circuits. Each charge channel can charge one or more than one battery. fro example, it is common for a AA, and AAA battery charger to have four charge stations and two charge channels. This means that each charge channel charges two batteries in the same circuit. This is why you see lots of folks recommend that you keep your batteries in sets to optimize their charging. Mostly, this is recommended because you are probably using a charger that has two batteries in each charge channel, like our TurboCharger 4000 for example.

What is a charge station?

In a battery charger, the charge station is where you place the battery to recharge it. Many battery chargers have charge stations that accommodate multiple kinds and sizes of batteries. For example, most AA chargers will also accept AAA batteries, and some “universal” chargers will accept other kinds as well in the same charge station. e.g.- AA, AAA, C, and D cells. Still other kinds universal chargers have adapters that come included, or must be obtained separately, to use different kinds and sizes of batteries.

What makes a charger a “smart charger”?

Any charger that uses a computer chip to control various aspects of the charging process can be considered a smart charger. Technically even a charger that can detect and adjust the charge rate based on the battery inserted into the charge station can be considered a smart charger, but anything that is either manual (steady charge rate as long as it is plugged in) or uses a timer to manage the charging process, we do not consider a true smart charger. There are even various levels of smart chargers. Different features that work together, sometimes in mysterious ways because there are just so many variables with batteries and chargers. In order for us to consider a battery charger a smart charger it needs to have a common charging feature known as negative delta V. Negative delta V is basically a technical method for a charger to know when a battery has reached its charge capacity and then shut the charging off, or sometimes change to trickle charge mode. Other features that contribute to a battery chargers “smart” status are: battery rescue (implemented in various ways to attempt to “jump start” an overly discharged battery – i.e. less than 1.0 or 0.9 volts – so that it will take a charge), temperature sensors, discharge and conditioning features, battery test features and even timers to limit the total length of the charge so even if you leave it plugged in, it turns itself off after a preset time. Remember, all manufacturers consider their chargers “smart” with any or all of these features and they are not all the same!? Hey, neither are we for that matter…