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Proper Care and Feeding: NiMH Battery FAQs

Proper Care and Feeding of a NiMH Battery

Q: What does NiMH stand for?

A: The material is Nickel Metal Hydride (NiMH) which has many advantages over other battery construction materials.

Q: What is meant by battery memory?

A: Older generation and batteries with other chemical make-up were subject to a memory effect. This is when a battery must be fully drained before recharge or their capacity is reduced. The New Generation of NIMH batteries do not develop a memory effect and can be recharged at anytime during usage cycle. When uncertain about battery charge level or condition, recharge it.

Q: What is the mAh rating mean?

A: This is a rating of energy storage capacity mAh = “milli-ampere hours”. So if you are comparing batteries to a AA with a 2000 mAh rating, it will have twice the capacity of a 1000 mAh rating.

Q: What is the best application for NiMH batteries?

A: Most all applications where there is a high energy consumption and demand, is where NiMH belongs. The most popular applications are digital cameras, flashlights, and toys. If you find yourself constantly buying alkaline batteries for an application, then you should consider using rechargeable NiMH.

Q: How many times can a NiMH battery be recharged?

Rechargeable NiHM BatteriesA: Lower capacity rechargeable AA batteries of 1700 up to 2000mAh can be recharged up to 1000 times in overnight slow charge mode, while 2100 to 2400 mAh rechargeable batteries can be recharged up to 600 to 800 times in overnight slow charge mode.

The new higher capacity AA 2500 mAh rechargeable batteries have greater power capacity, but   they can only be recharged approx 500 times in the overnight mode. Capacity improvement or quick charging will always decrease the number of cycles. Every cell available on the market above 2100 mAh will have below 1000 charge cycles.

Q: What applications are not good places to use NiMH batteries?

A: Any situation where the battery is not used within a 30 day period or low energy draw devices, for example smoke alarms, emergency flashlights, clocks, TV remotes, etc.

Q: Why won’t NiMH batteries work in some applications such as smoke alarms?

A: NiMH batteries self discharge about 1% per day so if used in a low energy consummation or stand-by device, the battery will only last about 90 days before requiring recharge.

Q: Can I use a higher rated mAh battery in my electronic device (i.e. 1800mAh vs. 2000mAh)?

A: Yes, the mAh rating will give you longer run times between recharges. The higher rated mAh of a battery has no effect on electronic devices other than they allow longer term use.

Q: Why are AA and AAA batteries rated at 1.2 volts and alkaline batteries rated at 1.5 volts?

A: In fact, over the course of their discharge, alkaline batteries actually average about 1.2 volts. 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 almost 80% of their discharge cycle. Once alkaline batteries discharge to 50% capacity, it will be delivering a lower voltage than a NiMH battery.

Q: What you NEVER want to do with replaceable batteries?


  • Never mix batteries from different manufacturers
  • Never mix batteries of different capacities
  • Never mix batteries of different chemistries, i.e. NiCd, NiMH, Lithium, etc.
  • Never DROP the battery if you can help it as NiMH batteries damage internally quite easily
  • Never store NiMH in the refrigerator
  • Never expose to extreme heat

Q: Do NiMH batteries lose capacity over time?

A: Yes, but nothing drastic. About 10 to 15% of the battery mAh capacity will be lost at the 400 to 800 recharge level. This will vary greatly because of battery and charger quality, along with how the consumer treats their batteries.

Q: When I receive my batteries do I need to charge them?

NiMH RechargerA: Yes, before you use them for the first time, you need to charge your NiMH batteries fully. Please note that for new NiMH batteries, it is often necessary to cycle them at least three to five times or more before they reach peak performance and capacity. The first several times that you use your NiMH batteries you may find that they run down (discharge) quickly during use. Don’t worry, this is normal until the batteries actually structure internally.

Q: Is there a difference in chargers. i.e, fast, slow, microprocessor controlled, etc?

Tenergy NiMH ChargerA: Yes, there are differences in the different chargers on the market today. If the charger was designed and sold in the past couple years and specifically says it is made to charge NiMH batteries you are probably okay. Most of the new chargers use a small computer chip to manage the charge and you should be getting at least 500 charges from your batteries. If not, buy a new charger. Some of the no name batteries sometimes have a short life. Fast chargers also tend to give shorter battery life of less than 500 charges.

Q: How do dispose of old NiMH batteries?

A: This is an easy one! While it is safe and legal in most states to dispose of your NiMH battery in your regular trash, we always encourage recycling whenever possible.

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139 people commented, TECH, Phil Purnell-Webb, Tech, Sher, and 135 others
This article is rated 4.6 out of 5
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Should contain only letters, numbers, and (' - .)!

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  • Phil Purnell-Webb
    My solar lights use NiMh 1.2v 600mAh batteries. Can I replace them with (say) 2300mAh ones?

    Reply  •  Rated article 5  •  December 28, 2022 at 12:05 am
    • TECH
      You can go with a higher-capacity battery as long as you stick with the same voltage and chemistry battery.

      Reply  •  Rated article 5  •  December 28, 2022 at 8:55 am
  • Sher
    Hi. I have a sonic toothbrush with NiMH battery. I fully charged it, thinking my old sonic wasn't usable. I got the old one working and might not need the new one for a while. Will it damage battery to not use the now-charged new one for maybe a year?

    Reply  •  Rated article 5  •  June 29, 2022 at 5:09 pm
    • BatteryStuff Tech
      It is recommended to store NiMH batteries at approximately 40% SOC to reduce age related capacity loss. Most NiMH batteries can be stored at this capacity for 3 to 5 years when stored at this level.

      Reply  •  Rated article 5  •  July 1, 2022 at 10:01 am
  • Talia K
    I have a Philips XL430 cordless phone. Unfortunately I cannot use its NIMH 550 mAh batteries anymore as I have damaged one of them. I have replaced them by two fully charged GP 930 mAh batteries, however the phone does not charge and the screen says 'no battery'. What can be the reason? Thanks in advance.

    Reply  •  Rated article 5  •  October 18, 2021 at 3:11 pm
    • BatteryStuff Tech
      Talia, if you match the intended voltage and chemistry and you are getting no battery detected I would theorize that Phillips may be preventing consumers from using after market batteries by putting a chip in the battery to let the phone know its a genuine battery and OK to charge. We have seen this done with laptops and other devices, but to be honest i haven't seen this done with a phone, although we do not sell phone batteries, so I cannot tell you for sure.

      Reply  •  Rated article 5  •  November 1, 2021 at 8:48 am
  • Talia K
    Answered all my questions and more. Thanks!

    Reply  •  Rated article 5  •  October 18, 2021 at 1:08 pm

    • Great

      Reply  •  October 29, 2021 at 3:15 pm
      • Daniel Baldwin
        Great 2

        Reply  •  October 29, 2021 at 3:59 pm
        • Daniel Baldwin

          Reply  •  October 29, 2021 at 4:17 pm
          • Daniel Baldwin

            Reply  •  October 29, 2021 at 4:19 pm
  • Ronald Johnson
    Can I put these batteries in outdoor solar charged devices

    Reply  •  Rated article 5  •  September 27, 2021 at 12:32 pm
    • BatteryStuff Tech
      NiMh batteries are used in a lot of solar equipment. Realistically, we recommend sticking with the same voltage and chemistry that came with your solar charging equipment as the solar panel for that unit is most likely geared toward that chemistry.

      Reply  •  Rated article 5  •  November 1, 2021 at 10:15 am
  • Denise Meier
    can solar powered batteries be put in rechargeable battery chargers

    Reply  •  Rated article 5  •  May 9, 2020 at 10:58 am
    • BatteryStuff Tech
      Most smaller solar lights contain NiMH or Lithium batteries that can be recharged with plug in charger. In the end you just need to verify the charger is meant to charge the that style battery. If you looking for a charger we do carry a couple chargers by Tenergy that are meant to charge smaller cell batteries.

      Reply  •  Rated article 5  •  May 11, 2020 at 8:57 am
  • Armand Boisvert
    I have NIMH batteries that came with my portable phones in 2017 the phone is acting very static breaking up how do I know when it’s time to buy new NIMH batteries

    Reply  •  Rated article 5  •  March 26, 2020 at 8:26 am
    • BatteryStuff Tech
      Typically, a reduction in capacity or talk time is going to be the sign its time to replace the battery. However, weak batteries generally aren't a cause for static. Static on the phone is typically relate to other causes such as weather (moisture on phone lines), faulty cable between wall and receiver, other devices on the phone line (DSL), faulty DSL Filter, or a fault in the house wiring maybe caused by a pest.

      Reply  •  Rated article 5  •  March 27, 2020 at 7:33 am
  • Jim
    The article says i may need to cycle the batteries a few times to get peak charge but it also states not to fully discharge the batteries. How far should they drain before I recharge them to achieve a proper “cycle” to help structure the batteries?

    Reply  •  Rated article 5  •  June 24, 2016 at 7:55 pm
    • BatteryStuff Tech
      The article didn’t say you shouldn’t fully discharge the batteries. In fact fully cycling the battery when you first start to use it will help form the battery internally. We recommend you fully cycle them at least three to five times before they reach peak performance and capacity. After that feel free to recharge whenever you see fit, as the these batteries do not have memory effect.

      Reply  •  January 18, 2017 at 1:53 pm
  • Stark
    Hello I have a remote controlled heli opterbut it seems it has a battery problem it does not charge so one day I removed battery and connected it with dry cell it underperformed but worked,the battery which I removed from helicopter was a small 3.7 v 85 mah rechargeable battery so the question is now which battery do I use in order to replace the helicopter battery and bring back to working plz tell me reply fast

    Reply  •  May 26, 2016 at 1:18 am
    • BatteryStuff Tech
      You want to replace it with the same voltage and chemistry battery. Your mAh can differ, but generally you want to go with one that is the same rating or higher. If you go with a higher rated battery just make sure it will still fit, and be aware it will take longer to charge.

      Reply  •  Rated article 5  •  May 26, 2016 at 2:19 pm
  • William McCollin
    Good info all through the questions

    Reply  •  Rated article 5  •  May 20, 2016 at 2:50 pm
  • AL
    Excellent information. Thank you.

    Reply  •  Rated article 5  •  December 28, 2014 at 9:25 am
  • Chandrasekhar
    Tons of info..Excellent, Excellent & Excellent notes verrry useful

    Reply  •  December 23, 2014 at 7:03 am
  • Nona Ebol
    i bought this digital power charger w/ 4 pcs 600mah rechargeable batteries.. i tried to charge it but its too hot, both charger and the batteries, am afraid it will blast so i remove the charger.. is it ok if its too hot? and can i use the rechargeable batteries to solar garden lights?

    thanks and more power!

    Reply  •  December 8, 2014 at 4:34 am
    • BatteryStuff Tech
      Batteries will generally be warm to the touch during charging, but should be hot. If they are hot than their might be an issue either with the charger, or the batteries. I would contact the manufacturer of our charger to be sure. As far as your solar lights you would want to use the same type of battery that was installed in the light.

      Reply  •  Rated article 5  •  January 2, 2015 at 1:10 pm
  • Wayne
    I would like to know if I replace my current cordless phone battery with a higher capacity rechargeable battery.
    For example, currently the battery that comes with the phone is using a 450mah capacity battery. Can I use a 1000mah or even a 2100mah rechargeable battery ? If its possible, does that means that the charging will takes a longer time and the usage time will be longer too ?

    Reply  •  Rated article 5  •  December 4, 2014 at 12:23 pm
    • BatteryStuff Tech
      As long as the voltage stays the same you can utilize a higher mAh battery. You are correct in regards that it will simply take longer to charge.

      Reply  •  Rated article 5  •  January 2, 2015 at 8:02 am
  • Manu
    Hi, thanks for the article. Can you tell me what happens when you use a rechargeable Ni-mh 2100 with a normal AA battery? Did I damage the Ni-mh? Thanks!

    Reply  •  Rated article 5  •  November 14, 2014 at 3:42 pm
    • BatteryStuff Tech
      Mixing and matching battery chemistry is never recommended it is quite possible it damaged the battery.

      Reply  •  Rated article 5  •  November 19, 2014 at 11:05 am
  • Shannon
    You do not list cordless phones among the electronic devices that use these rechargeable batteries. I have a Panasonic cordless phone that takes Ni-MH 1.2v AAA batteries. Will any rechargeable Ni-MH AAA work in my phone?

    Reply  •  Rated article 4  •  November 11, 2014 at 8:13 am
    • BatteryStuff Tech
      Yes, however I would make sure that you replace the battery with a same mAh rating or greater so the phone last as long, or longer.

      Reply  •  Rated article 5  •  November 19, 2014 at 12:59 pm
  • MedicalGenius
    Interesting article.

    Question: If an EKG machine with an NiMH battery were to be unused for six weeks, what action(s) should one take to prevent premature wear of the accessory? Should the equipment remain plugged in, keeping the battery’s charge at full capacity?

    Also, what is minimum temperature and/or humidity levels it is safe to store NiMH batteries?

    Thank you.

    Reply  •  Rated article 3  •  October 30, 2014 at 7:41 am
    • BatteryStuff Tech
      We have posted your question to the forum, but we are unable to offer in regards to support for a medical device. I believe it would be best to contact the manufacturer for their recommendations.

      Reply  •  Rated article 5  •  November 19, 2014 at 8:43 am
  • SpongBob
    Question: What temperature and humidity range can a NIMH be safely stored in? We have three EKG machines located in trailers. We would like to lower the temperature within those structures since they won’t be occupied for six weeks. How best can we conserve energy and ensure that the batteries inside the EKG machines aren’t harmed? Should the batteries simply be removed? The units are kept plugged in 24/7.

    Thank you.

    Reply  •  October 28, 2014 at 12:04 pm
    • BatteryStuff Tech
      I believe it would be best to contact the manufacturer of the EKG machines and verify their operating temperature. Most manufacturers will provide an operating temperature range for their devices to ensure they work properly.

      Reply  •  Rated article 5  •  November 19, 2014 at 7:30 am
  • Ambrish
    Can I use a battery with higher mAh than originally provided with my camera ? Will the same charger work for new battery as well ?

    Reply  •  October 28, 2014 at 9:10 am
    • BatteryStuff Tech
      You can us a battery with a higher mAh, and the plus side is that it will last longer. However your charger will take longer to recharge a higher capacity battery.

      Reply  •  Rated article 5  •  November 19, 2014 at 7:27 am
  • AVG
    I have just received a new phone battery. Based on other purchase experience When I put it in the phone I know it will contain some charge already. Is it best to charge it fully straight away? or let it run down and then fully charge? thanks

    Reply  •  Rated article 5  •  October 14, 2014 at 7:00 am
    • BatteryStuff Tech
      The New Generation of NIMH batteries do not develop a memory effect and can be recharged at anytime during usage cycle. When uncertain about battery charge level or condition, recharge it.

      Reply  •  Rated article 5  •  November 18, 2014 at 10:36 am
  • Tep
    Really like the article! I do have a question about batteries though: I have a device which is running on two AA Duracell batteries. The batteries (brand new) together is producing 3.2 volts (1.62 volts individually), which is estimated to run for at least 2 years. The device is constantly running and consumes about 300 Micro amps, which is not a lot. I was wondering, when might the batteries voltage begin to drop from 3.2 volts to 3.0 volts or lower? After constantly being used for a month straight, will it then begin to drop?

    Reply  •  October 13, 2014 at 2:59 pm
  • ROZ
    I have a Duracell GoEasy charger (a few years old now) that came with AA NiMH batteries marked with 1700mAh and see newer AA NiMH batteries with 2400mAh. Can I use the newer 2400mAh AA batteries in this charger?

    Reply  •  Rated article 4  •  October 9, 2014 at 10:19 pm
    • BatteryStuff Tech
      Yes, it would just take a little longer for the charger to charge as it is a higher capacity.

      Reply  •  Rated article 5  •  November 18, 2014 at 7:46 am
  • Maggie
    Hi there… I replaced my solar garden batteries with new ones , because the old ones would not charge out side in the sun light anymore . ( I Use them in in strings of 50 small bulb fairy garden lights ) I ordered exactly the same batteries that were used in the solar panel for the lights, and they arrived uncharged. My problem is, that although I have put them in a battery charger several times to fully charge, they do not hold their charge for long, and the lights will not work for more than a couple of nights. The bright sunlight does not seem to power them up again during the day light. I have to keep taking them out of the panel to recharge every two to three days which is very annoying as the old batteries gave the lights life for about a year before they died. Any ideas what I am doing wrong ? Thank you so much … Maggie :)

    Reply  •  October 7, 2014 at 7:13 am
    • BatteryStuff Tech
      It sounds as if either the light conditions have changed where this string of lights are, or the battery capacity is not the same as before. If the battery capacity is less than before that would mean there was less reserve for bad weather days, which would mean the batteries last less.

      Reply  •  Rated article 5  •  November 17, 2014 at 2:19 pm
  • Wanda
    Can NiMh batteries be replaced with alkaline batteries? Thanking you in advance.

    Reply  •  August 20, 2014 at 10:39 am
    • BatteryStuff Tech
      In the application, usually yes, but not in regards to charging.

      Reply  •  August 22, 2014 at 9:42 am
  • K
    how much longer does a 2300mah battery last compared to a 1700mah

    Reply  •  August 7, 2014 at 11:59 pm
    • Admin
      It depends on your load, but it should increase you battery life significantly.

      Reply  •  August 15, 2014 at 2:33 pm
  • Elsa
    I just read your article and the questions and comments. I think you may have answered my problem, but my specifics are a little different so I thought I would ask. I bought a new unopened box of Journey’s Edge Solar powered Outdoor lanterns from a yard sale vendor. The batteries seem to be in need of recharging. They are NiCd AA600mAh 1.2V. batteries.
    I have some Energizer rechargeable AA 2500mAh 1.2 v batteries. I also have a Sanyo Ni Mh recharger. I am recharging the Ni Mh batteries now, but can I use these higher mAh batteries in my solar lights? Also should I try to recharge the Ni Cd 600 mAh ones that came with the lights in my Ni MH recharger? Will it harm the batteries or the recharger?

    Reply  •  Rated article 5  •  July 30, 2014 at 10:19 am
    • Admin
      Due to the fact that we don’t have all the information for your system we would need you to contact us at so that we can ask the appropriate questions, to get you the answer that you may need.

      Reply  •  August 15, 2014 at 2:31 pm
  • M Dawson
    Hi ,I have purchased some batteries for my solar string lights Ni-MH AA 600mah 1.2 v but they have come uncharged. I found a cheapish charger at the weekend but the charge is considerably higher … 1200 mah if i remember rightly. Is it ok to buy ? Could i also recharge the original spent batteries…. Maybe I should not have bought new batteries first.. doh ! Please help…. Thankyou


    Due to the fact that we don’t have all the information for your system we would need you to contact us at so that we can ask the appropriate questions, to get you the answer that you may need.

    Reply  •  July 7, 2014 at 9:23 am
  • M Dawson
    I have just purchased some AA Ni-Mh 1.2v 600mAh batteries to replace those used in my garden solar lights.Could i have just recharged the old ones instead of buying new ones? Also,can the new ones be charged in a charger used for 1200mah. Confused lol …Thankyou

    Due to the fact that we don’t have all the information for your system we would need you to contact us at so that we can ask the appropriate questions, to get you the answer that you may need.

    Reply  •  July 6, 2014 at 3:29 pm
  • Gary
    I’ve just purchased some AA 2400 MaH batteries for my solar lights. I’ve just noticed that the batteries that they are replacing are 600MaH. Will this make any difference to them working and also am I better off fully charging the batteries beforehand like you mentioned above (I think the answer is no to the seconfd question in this case !).
    Please help,

    Reply  •  June 23, 2014 at 9:31 am
    • BatteryStuff Tech
      It will make a difference. I would recommend charging them fully before use.

      Reply  •  June 25, 2014 at 8:55 am
  • BatteryStuff Tech
    Always check with the manufacturer.

    Reply  •  June 16, 2014 at 10:56 am
  • Irfan
    can i use 3000mah battery instead of 2000mah battery(recomd.) in my micromax canvas 2 colors A120 because it is causing heating problems and has low battery life… will dis change affect my phone ?

    Reply  •  Rated article 5  •  June 11, 2014 at 5:49 am
  • Alan
    Great article, interesting read!
    Could you help with my question? I have just bought a second hand a snap on diagnostic scanner that has an 8.4v NI-MH rechargeable battery that doesn’t hold its charge; I am going to replace this battery. The scanner comes with its own built in trickle charger and a separate battery only trickle charger both of which share the same power lead adapter. I noticed that this power lead adapter was not a snap on original but a Stontronics VE50-1500. The specs of the trickle charger require 14-16v dc input at 36W but the output of the Stontronics is +15v dc 3.4A at 50W, would this be overcharging the battery and could this be why the battery does not hold its charge? Thanks.

    Reply  •  June 6, 2014 at 2:39 pm
    • BatteryStuff Tech
      Alan, it could be. I would recommend contacting the manufacturer about this issue.

      Reply  •  June 16, 2014 at 10:26 am
  • Doug
    Is there a measurement for which I could use a multi-meter to determine if a NI-MH battery is still above 50% capacity/life? I have some that haven’t been charged that much and different chargers indicate they are fully charged, but they are clearly not when I place them in a digital camera or other higher current devices.

    Reply  •  June 5, 2014 at 7:29 am
    • BatteryStuff Tech
      Because they hold their voltage constant for so much of their discharge cycle, it would not be possible to do so.

      Reply  •  June 6, 2014 at 8:50 am
  • Lee
    I use a set of wireless headphones 900 mhz . They came with 550 Ma NiMh and they work fine. When I switch to New Duracell 800 Ma NiMh the headphones have a popping sound. Switch back to orig. AAA and all is fine again. Any ideas?

    Reply  •  Rated article 5  •  June 5, 2014 at 7:24 am
    • BatteryStuff Tech
      Sometimes there is a slight voltage difference between brands that can lead to some electronics working better on one brand than another.

      Reply  •  June 6, 2014 at 8:48 am
  • Simon
    I have a 9.6v nimh 800 mah battery pack for a Tonka toy truck. I’m looking to buy a smart charger for it but some of them are saying only use on 1500 mah or higher. If it’s a smart charger, will it hurt an 800 mah battery? If I buy a charger that comes with a new 2000 mah battery pack, will that somehow hurt the toy truck? If I’m understanding the article and comments correctly, it sounds like 9.6v is what matters and the higher mah will just take longer to charge and last longer. Am I right?

    Reply  •  June 3, 2014 at 2:09 pm
    • Admin
      It depends on the charger. It would be best to ask the manufacturer of the charger this question, as it will be different from charger to charger. Thanks

      Reply  •  June 4, 2014 at 8:59 am
  • BArBF
    I got 15 solar pathlights and 12 of the batteries in them would not charge. They are located in bright bright sunlight. label says AAA rechargeable battery can be replaced with up to 900 maH. The original maH is 150. These were cheapos but nice looking bulbs. For the ones that DO work, what advantage would there be to replace with the 900 maH?
    And would charging under indoor light be sort of the same as cycling the batteries on a charger? Can you OVERcharge these batteries that way? (duh here) lol

    THanks so much!

    Reply  •  Rated article 5  •  May 22, 2014 at 11:19 am
    • BatteryStuff Tech
      You have to make sure the charger you use is compatible with nimh batteries, which will depend on the charger. 900mAh will last a lot longer, but they will also take longer to charge.

      Reply  •  May 23, 2014 at 2:02 pm
  • Al
    Can you leave a Ni-MH battery on the charger indefinitely without damage – i.e. we have a small cordless vcaccum with a Ni-MH batter and a A/C plug in charger, and it says to toally dischargfe before re-charging – thedn requires 16 hours to recharge – making it troublesome if it runs down during use. If I forget to unplug it will damage occur – or if I just leave it plugged in will it overcharge/damage the battery? Help!!

    Reply  •  Rated article 3  •  May 13, 2014 at 9:46 am
    • BatteryStuff Tech
      It depends on the charger. That question would be best answered by the charger manufacturer.

      Reply  •  May 14, 2014 at 10:35 am
  • Samer
    an awesome article thanks man but i have a question ……..
    if a have a battery 5 v / 1 mah can i charge it with a 5 v / 1.5 mah charger or a power bank ?

    Reply  •  Rated article 4  •  April 24, 2014 at 5:53 pm
    • Admin
      Please email with your question.

      Reply  •  May 14, 2014 at 10:33 am
  • JIm H.
    Question: Do Ni-MH batteries lose power – amperage (like a car battery would)? In other words, the voltage is 2.4V, the appliance (beeper) lights up but doesn’t vibrate.

    Reply  •  April 22, 2014 at 4:14 pm
  • Effem
    Is it safe to use Ni-Cd battery charger to charge Ni-mh batteries? What are the precautions if I will do this? Another question: Can I charge different brands of AA Ni-mh batteries at one time in a 4-slots battery charger?

    Reply  •  March 30, 2014 at 12:08 am
  • Vladan
    Wow! Very helpful, thank You!!!

    Reply  •  Rated article 5  •  March 26, 2014 at 8:18 am
  • Steve
    I have a radio that uses 4 AA batteries. When I put alkaline or NiCad batteries in it works fine. I recently purchased NiMH batteries to use in it and charged them up. My multimeter says they have almost 1.35 volts each and the amperage measures higher than the NiCad batteries — but when I install the NiMH batteries, the radio doesn’t show anything, no clock, no battery level, nothing. It looks like there are no batteries in in at all. When I put the NiCad batteries with lower voltage and amperage readings back in it fires right up. Any thoughts as to why?

    Reply  •  Rated article 5  •  March 21, 2014 at 4:23 pm
    • Terry
      I was just reading through and I am no expert like some of the others here but it looks like your radio requires 1.5 volt batteries and you are trying to replace them with the 1.2 volt NiMH.

      Reply  •  April 30, 2014 at 11:00 am
  • Kurt
    So I wonder if someone can help. I have a communicator for a helmet that runs on a NI-MH battery. The battery pack says 4.8v 1000mah. The charger that came with the unit is a 12V 300ma charger. I also have one from a small cordless drill that is 12V 200ma. Is it better to charge is with the 200ma? Just curious if that is a slower charge and if so it is a better way to go for longevity of the battery? Thanks!

    Reply  •  Rated article 5  •  February 16, 2014 at 11:47 am
  • Jim O
    I have a Cobra two-way radio set. It came with SANIK NiMH batteries, 1200mAH. When the radios are placed in the charger, the LEDs light up and they seem to charge and all is well. When one of the batteries went bad, I replaced them with LENMAR R2G NiMH bateries, 1.2 volt but with a 2150 mAH rating. They don’t seem to charge, and the LED indicator doesn’t come on. The charger instructions say you can leave the radios on the charger even after the battery is charged.

    So, is there some reason the longer life batteries won’t charge? Am I stuck with only the shorter life batteries (which I can’t seem to find)?


    Reply  •  Rated article 4  •  November 29, 2013 at 3:34 pm
  • R Woods
    Outstanding site. Exactly what I was looking for and the information on more modern batteries was very interesting. Guess I‘ll have to check out your home web site. Thanks, r woods

    Reply  •  Rated article 5  •  August 14, 2013 at 4:34 pm
  • JT
    Great write-up. Much more clear and concise, and with a more user friendly presentation than most articles I have read (although they were intended for a different audience).

    QUESTION: At what percentage of the rated capacity should Ni-Mh and Ni-Cad batteries be replaced?

    Example: An 1800mAh Ni-Mh battery is now cycling (discharge / charge with a microprocessor controlled charger) with a full charge at 1200mAh. Thus, the battery is now at 67% of its’ rated capacity. How do you decide if it needs to be replaced? (These numbers are just an example, not representative of my actual batteries). If it matters, they are used in High-end 2 way radios.

    Reply  •  Rated article 4  •  August 9, 2013 at 9:59 am
  • Ashton Grave
    very comprehensive & useful article. I have replaced nicad 1.2v AA batteries in a solar sensor light with great results. whatever the nature of the cheap solar panel charging current etc is, it seems to work fine.

    Reply  •  August 6, 2013 at 10:52 pm
  • Fast Robert
    Really clear & helpful

    Reply  •  Rated article 5  •  July 25, 2013 at 10:50 pm
  • Adel Salem

    Reply  •  Rated article 5  •  June 22, 2013 at 7:49 am
  • Daveboy
    I was confused regarding rechargeable AA batteries,I have been using NI-CAM with poor results,I have now
    changed to NI-mh,hopefully the dreaded “Memory syndrone” is a thing of the past.

    Super article Tank you

    Reply  •  June 21, 2013 at 3:50 am
  • Autumn
    I just wanted to let you know that this article was extremely helpful and useful. I now have the answer I need to make my battery purchase. Thank You!

    Reply  •  Rated article 5  •  May 30, 2013 at 2:47 pm
    • Jeremy Fear
      You‘re Welcome~!

      Reply  •  May 30, 2013 at 2:51 pm
  • Chuck
    I have a rayovac rechargeable alkaline labeled 1.5v. are they still available?
    Thanks for the help

    Reply  •  May 30, 2013 at 1:13 pm
    • Jeremy Fear
      Yes they are! Follow this link:

      Reply  •  May 30, 2013 at 1:36 pm
  • AbhinayD
    Kodak Ni-MH Rechargeable Battery heat up while it a problem..plzz help

    Reply  •  Rated article 4  •  May 21, 2013 at 5:36 am
    • Jeremy Fear
      It may be. I would recomment contacting the manufacturer to find out the heat tolerance of those batteries, and measure the temperature accordingly.

      Reply  •  May 21, 2013 at 11:49 am
  • Shaz
    i have 2 nimh 1.2v rechargable batteries. I got a 11v battery charger from old stuff…can i use it to charge my battery..? Or how much volt will need to charge that batteries? I like to build circuits.. can i modify my charger?

    Reply  •  May 21, 2013 at 1:14 am
    • Jeremy Fear
      No, that charger would not be able to charge those batteries. Only a proper charger that is configured for NiMH charging is recommended.

      Reply  •  May 21, 2013 at 11:49 am
  • Dick
    This was a great article. When I first used solar lights in the yard and the batteries eventually failed I could not find 400maH ones anywhere. I succeeded in locating 1000maH by mail order from China. I always worried that the difference in spec would be a problem but I could not find any information on the Web about it then. Yours is the only article that discussed the point, and I‘m glad to find out that difference in specs is not a problem.

    Reply  •  Rated article 5  •  April 20, 2013 at 11:37 am
    • Jeremy Fear
      We are glad you found it to be helpful! :)

      Reply  •  April 24, 2013 at 9:32 am
  • Betty
    Great tech support here!

    Reply  •  Rated article 5  •  March 14, 2013 at 6:48 am
  • Chohan
    i have got 3 x makita 18v 2.6ah nimh batteries

    now the problem is these batteries show full charge on multimeter and they hold that full charge as if you see after 10 days of charging the batteries will show full charge on multimeter…..the batteries give good spin to the drill but if i apply pressure with my hands i can stop the drill

    why is this???

    remember the good 18v batteries you cant stop the drill with your hands

    so why they not performing well under LOAD

    answer will be much appreciated


    Reply  •  February 23, 2013 at 3:27 am
    • BatteryStuff Tech
      I don‘t know why they aren‘t performing well under load without testing them. Are they old batteries? Maybe you should consider replacing them.

      Reply  •  February 25, 2013 at 9:34 am
  • Dmac
    Hi, I bought a digital camera and the sales guy told me to charge my Kodak Ni-MH batteries for 4 hours before use, I charges for 6 hrs. I assumed I should charge for 4 hrs every time but the battery manual recommends 11.5 hrs. Should I listen to the sales guy or charge as per the manual. Or does anyone know how long I should charge my batteries?

    Reply  •  Rated article 4  •  February 18, 2013 at 10:21 pm
    • BatteryStuff Tech
      Maybe the batteries were only partially charged when you bought them. Sometimes the batteries are fully charged when the leave the factory, but when they sit on the shelf for months they do drain some. By the time you buy the batteries, they could be only 70% capacity remaining.

      As long as the charger is an automatic charger, there really is no harm in charging the batteries for 4, 6, or 11.5 hours regardless of the state of charge on the batteries. Once they reach full capacity, hopefully the charger should stop charging.

      Reply  •  February 19, 2013 at 8:57 am
  • Gabe
    It didn‘t dawn on me to look into the details of my AAA batteries and I‘m wondering if I may have screwed up an antique device of mine.
    Device requirements: AAA alkaline batteries (It‘s an old device – a well-preserved Handspring.)
    What I put in there: NiMH AAA batteries (Eneloop)

    What happens in cases like these?
    Many thanks.

    Reply  •  Rated article 5  •  February 18, 2013 at 6:40 pm
    • BatteryStuff Tech
      As far as the device is concerned, the AAA battery size will determine that the battery (whether Alkaline or NiMH) will have the proper voltage output. Capacity may differ, but that only affects runtime for the device. Rechargeable NiMH batteries are a compatible replacement for the one-time use Alkaline batteries.

      Reply  •  February 19, 2013 at 8:53 am
  • Julia
    I want to buy an adapter for my car since it is too old to have the place to be able to plug in and listen to my Ipod. I always heard that just a plane invertor is too high a voltage. If I get a 2100 amh charger, will I be able to play my Ipod off of it without damage? Same for a cell phone?


    Reply  •  February 7, 2013 at 7:21 am
    • BatteryStuff Tech
      Do both your ipod and cell phone run on NiMH batteries?

      Reply  •  February 7, 2013 at 9:32 am
  • Bruce
    I just got a OFNA Receiver Pack 110V AC NiMH Wall Charger 10214. It is rated at 6v output, but is showing 11.48v on a meter at the connector. Is this usual to this type charger? It is specifically for NiMH charging on the label, so maybe the circuitry turns up the voltage at initial hookup? I just bought this to charge a 4 pack of 2000ma AA size batteries. The charger is very warm to the touch with a red charging LED showing. No instructions came with it.

    Reply  •  Rated article 5  •  January 8, 2013 at 7:26 pm
    • BatteryStuff Tech
      I cannot confirm if that behavior is normal since we do not sell that particular model charger. I recommend checking with the manufacture of the charger for technical help.

      Reply  •  January 9, 2013 at 8:44 am
  • Matt
    Great article. My question … our video baby monitor came with three 1.2V 2000 mAh NiMH batteries in the handheld monitor. We charge them using the supplied cable that just plugs into the handheld monitor. The batteries that came with the monitor are slowly dying so I would like to replace them. Will any brand of AA NiMH battery from a local store do the trick?

    Reply  •  Rated article 5  •  January 6, 2013 at 3:25 pm
    • BatteryStuff Tech
      Yes. However, some brands may have higher capacity than others. 2000 mAH is like the size of the tank. It will run your monitor for longer than say a 1500 mAh battery. If you do your research, you can find high capacity AA NiMH batteries.

      Reply  •  January 7, 2013 at 9:10 am
  • Chris
    I have a Kodak digital camera (Easy Share Max Z990) that came with 4 rechargeable 1.2 volt NiMH AA batteries and a charger. Is it safe to use 4 alkaline 1.5 volt AA batteries instead?

    Reply  •  Rated article 1  •  December 18, 2012 at 11:38 am
    • BatteryStuff Tech
      Please refer to technical help from Kodak for the answer to your question. While it may technically work, we don‘t know if the voltage increase will cause any harm to the camera or not.

      Reply  •  December 18, 2012 at 11:52 am
  • Steven
    Very useful info – thanks. I bought a set of store brand 2450mAh AAs which I have been charging with an Energizer CHDC7. Strangely, two of the batteries now give the “bad” blinking indicator. Two seem fine. Is it common to have very different performance within a group bought in the same package?
    Also, I doubt I have charged them even 75 times, after mostly using them in digital cameras,(Over a two year period). Is there any justification to complain to the retailer?

    Reply  •  Rated article 4  •  December 9, 2012 at 10:09 am
    • BatteryStuff Tech
      We have experienced bad ‘batches’, but not single bad cells within a batch. But this does not give your situation any less validity. Have you measured the voltages of the batteries?

      Reply  •  December 10, 2012 at 9:55 am
  • Beatlearl
    I had to bookmark this site because I know smart when I see smart and after reading some of the articles on your site you guys are smart.

    Reply  •  Rated article 5  •  December 8, 2012 at 12:26 pm
  • BOB
    I have a question regarding this paragraph:

    “When I receive my batteries do I need to charge them?
    Yes, before you use your new NiMH batteries for the first time you need to charge them fully. Please note that for new NiMH batteries, it is often necessary to cycle them at least three to five times or more before they reach peak performance and capacity. The first several times that you use your NiMH batteries you may find that they run down (discharge) quickly during use. Don’t worry, this is normal until the batteries actually structure internally.”

    I purchased an electronic item with a NiMH battery and mistakenly didn‘t charge it as long as the manual said (it said up to 16 hours and I did it about 2 hours). After using it and wondering why the battery was already low, I looking in the manual and am now charging it fully. Since I didn’‘t fully charge it before first use, will that cause a problem for the battery?

    Thank you.

    Reply  •  Rated article 5  •  November 24, 2012 at 9:53 pm
    • Michael
      Thank you!

      Reply  •  Rated article 1  •  April 5, 2016 at 11:07 am
    • BatteryStuff Tech
      Not charging full capacity and discharging in the first initial uses can cause the memory effect. But there‘s also the chance the battery will be fine. Closely monitoring the capacity of the batteries would be the way to determine if there was any negative effect.

      Reply  •  November 26, 2012 at 2:15 pm
  • Mani
    Nice and useful information. thanks for sharing.

    Reply  •  Rated article 5  •  November 2, 2012 at 8:41 pm
  • Siddharth
    For how much time do i have to keep my 2100mAh NiMH batteries in charging???
    My charger doesn‘t have any indicator for the batteries, if they have fully charged….Plz Help me with the exact time!!!

    Reply  •  October 18, 2012 at 1:39 am
    • BatteryStuff Tech
      At what rate does your charger charge at? I would be surprised if the charger didn‘t indicate this information, either on the unit, AC adapter, or manual.

      Reply  •  October 18, 2012 at 8:14 am
  • Amin
    Which is the best battery 1000mAh or 2100mAh ? i use sony BCG-34HW2RN battery charger. Can i charge 2100mAh battery in this charger ? please reply

    Reply  •  Rated article 5  •  October 17, 2012 at 11:11 am
    • BatteryStuff Tech
      I am not familiar with the battery charger you mentioned, so I cannot answer that question. But the higher the mAh rating on a battery is, the more capacity it has. This translates to longer runtime for your application before needing to recharged again.

      Reply  •  October 17, 2012 at 11:20 am
  • Manoj A
    I am having CB-5AH NI-MH canon charger. Can i charge my batteries rated for 1000mA NI-MH. Thanks in advance. I would like to thanks you for giving wonderful understanding.

    Reply  •  October 16, 2012 at 7:49 am
    • BatteryStuff Tech
      Since we do not sell that specific charger, I cannot confirm if it will be safe to use on a 1000 mAh battery. 5 amps is too much to put into a 1 Ah battery, but if the charger is a smart charger, then it wouldn‘t matter. I recommend you contact the manufacture of the Cannon charger for the confirmation you‘re looking for.

      Reply  •  October 16, 2012 at 10:00 am

    Reply  •  October 13, 2012 at 8:28 am
    • BatteryStuff Tech
      This questions is like saying your cars holds 20 gallons. How long does it take to refill it? That depends entirely on how much is left and the rate the fuel flows through the nozzle at the gas station.

      The answer is: I don‘t know. As long as it takes? Usually a smart charger will have some light indicator informing you when the battery is fully charged.

      Reply  •  October 15, 2012 at 8:46 am
      • Luis
        I used to calculate the time to charge a 900mAh battery with a 200mA charger. The result is 5.4h. It was charging for about 23h, the light was still on (meaning it‘s not carged) when I stopped it. They are new, so I wanted to fully charge them. Is this normal?

        Reply  •  Rated article 4  •  January 14, 2013 at 7:05 pm
        • BatteryStuff Tech
          I recommend you measure the resting voltage of your battery pack. This will tell you the state of charge of the battery.

          Reply  •  January 15, 2013 at 9:16 am
          • Bob
            Measuring a battery at rest will not tell you the state of charge. You can read 1.2 volts on a battery that is almost dead, but once you put a load on that battery the voltage reading will drop greatly. If you want to measure voltage do it under load, believe me I know over 30years in the electrical trade.

            Reply  •  Rated article 2  •  April 27, 2014 at 10:28 am
          • EnewsDigest
            Thanks for the excellent article and detailed reply to all our doubts. My question is if I can measure the mAh remaining in a 1.2 V, 2700 mAh rechargeable battery with the help of a multi meter. The idea is that, then I can exactly recharge for a specific period of time without over charging the battery. Say for example, if I know that 2200 mAh is remaining I can charge for two hours with a charger with 250 mA output.

            Reply  •  Rated article 5  •  March 17, 2014 at 1:40 pm
  • Rajesh
    Can I use a charge for any battery capacity (say 400mAH to 2800mAH)? Or chargers are designed to use specific capacity?

    E.g. Can I use “Sony BCG-34HWN Battery Charger” for various NiMH batteries (say 400mAH to 2800mAH)?

    Reply  •  Rated article 5  •  October 9, 2012 at 12:52 am
    • BatteryStuff Tech
      If the voltage is nominal and the chemistry matches, you can tehcnically use the same charger. But keep in mind the charge rate is like current flow. If you have a larger capacity battery, it may take much longer to bring the charge up. Or if the current is too much for a small battery, it can damage it.

      Reply  •  October 9, 2012 at 4:06 pm
  • Ketan
    OK – my question: How many Watt-Hours can I squeeze out of a standard 450mAH 1.2V NiMH battery? Ineed to calculate scenarios, such as drive a 1 watt load for certain number of minutes etc.

    Reply  •  Rated article 4  •  September 25, 2012 at 12:40 pm
    • BatteryStuff Tech
      Watt’s Law: Wattage=Voltage X Amperage. A battery with the specifications you provided will have .54 Watt hours. A secondary issue which will affect your scenario is that draining a Nihm battery to 100% discharged will damage the battery and is not recommended. With your battery you could run a 1 watt load for about 30 minutes, though a little less, like 20 mins, would be recommended.

      Reply  •  May 30, 2014 at 10:06 am
  • Vicki
    Wow! This is very helpful and interesting info. I didn‘t realize there were certain devices where NiMH batteries should not be used, nor did I know the difference between charger types. Thank you for taking the time to educate us about these things. Warmly, Vicki

    Reply  •  Rated article 5  •  August 4, 2012 at 12:07 pm
    • AlexB
      This is the exact reason I have been researching the rechargeable Ni-MH batteries. I knew they were used for the 2-way radios but I wanted to check before using them in my headphones. I wonder if they heat up…?

      Reply  •  Rated article 5  •  May 20, 2016 at 10:31 pm
    • BatteryStuff Tech
      I‘m glad you enjoyed our article. Share it with your friends, if you haven‘t already done so. :)

      Reply  •  August 6, 2012 at 9:43 am
      • JanD
        I purchased a Coldheat chargable glue gun and the 4.8 chargable battery pack was already dead before its first use, what would cause unused rechargable battery’s to be dead before they have been charged? JanD

        Reply  •  October 29, 2014 at 8:34 pm
        • BatteryStuff Tech
          Some manufacturers send there battery packs only partially charged, and require you to charge the battery prior to use.

          Reply  •  Rated article 5  •  November 19, 2014 at 8:40 am