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Proper Care and Feeding of a NiMH Battery

Proper Care and Feeding of a NiMH Battery

What does NiMH stand for?

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

What is meant by battery memory?

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.

What is the mAh rating mean?

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.

What is the best application for NiMH batteries?

Most all applications where there is a high energy consumption and demand, is where NiMH belongs. The most popular applications are digital cameras, PDA’s, hand held games, portable music players, video devices and toys. If you find yourself constantly buying alkaline batteries for an application then you should consider using rechargeable NiMH.

How many times can a NiMH battery be recharged?

Rechargeable NiHM BatteriesLower capacity rechargeable AA batteries -1700 up to 2000mAh mAh can be recharged up to 1000 times in overnight slow charge mode. 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 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

What applications are not good places to use NiMH batteries?

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.

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

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.

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

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 that allow longer term use.

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

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.

What you NEVER want to do.

 

  • 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

Do NiMH batteries lose capacity over time?

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.

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

NiMH RechargerYes, 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.

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

Tenergy NiMH ChargerYes, 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.

How do dispose of old NiMH batteries?

This is an easy one! While it is safe and legal in most states to dispose of in a landfill, we always encourage recycling whenever possible.


 
61 Responses,   4.6 Rating

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  • 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

    Vicki
    August 4, 2012 a 12:07 pm
    • I‘m glad you enjoyed our article. Share it with your friends, if you haven‘t already done so. :)

      Tech
      August 6, 2012 a 9:43 am
    • 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.

      Ketan
      September 25, 2012 a 12:40 pm
      • Batteries do not discharge in a linear fashion. The higher the draw amount, the less duration of discharge you will experience. wattage is total power. According to OHM‘s Law, Watts = Volts x Amps. If your draw amount is 1 watt. 1 Watt = 1.2 Volts x 0.833 Amps (833 mAH). If your pulling 833 mAH from a battery rated at 450 mAH, I would be surprised if you even received 1/2 an hour of runtime.

        Tech
        September 28, 2012 a 8:59 am
      • 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)?

        Rajesh
        October 9, 2012 a 12:52 am
        • 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.

          Tech
          October 9, 2012 a 4:06 pm
        • AM USING KODAK DIGITAL CAMERA BATTERY OF 2000MAH AA 1.2V.HOW MUCH TIME DO I NEED TO RECHARGE THEM?

          DSANJIB
          October 13, 2012 a 8:28 am
          • 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.

            Tech
            October 15, 2012 a 8:46 am
            • I used http://www.csgnetwork.com/batterychgcalc.html 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?

              Luis
              January 14, 2013 a 7:05 pm
              • I recommend you measure the resting voltage of your battery pack. This will tell you the state of charge of the battery.

                Tech
                January 15, 2013 a 9:16 am
                • 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.

                  EnewsDigest
                  March 17, 2014 a 1:40 pm
          • 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.

            Manoj A
            October 16, 2012 a 7:49 am
            • 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.

              Tech
              October 16, 2012 a 10:00 am
            • 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
              Thanks

              Amin
              October 17, 2012 a 11:11 am
              • 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.

                Tech
                October 17, 2012 a 11:20 am
              • 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!!!

                Siddharth
                October 18, 2012 a 1:39 am
                • 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.

                  Tech
                  October 18, 2012 a 8:14 am
                • Nice and useful information. thanks for sharing.

                  Mani
                  November 2, 2012 a 8:41 pm
                  • 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.

                    BOB
                    November 24, 2012 a 9:53 pm
                    • 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.

                      Tech
                      November 26, 2012 a 2:15 pm
                    • 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.

                      Beatlearl
                      December 8, 2012 a 12:26 pm
                      • 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?
                        Thanks!

                        Steven
                        December 9, 2012 a 10:09 am
                        • 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?

                          Tech
                          December 10, 2012 a 9:55 am
                        • 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?

                          Chris
                          December 18, 2012 a 11:38 am
                          • 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.

                            Tech
                            December 18, 2012 a 11:52 am
                          • 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?

                            Matt
                            January 6, 2013 a 3:25 pm
                            • 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.

                              Tech
                              January 7, 2013 a 9:10 am
                            • 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.

                              Bruce
                              January 8, 2013 a 7:26 pm
                              • 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.

                                Tech
                                January 9, 2013 a 8:44 am
                              • Hi,
                                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?

                                Thanks!

                                Julia
                                February 7, 2013 a 7:21 am
                                • Do both your ipod and cell phone run on NiMH batteries?

                                  Tech
                                  February 7, 2013 a 9:32 am
                                • 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.

                                  Gabe
                                  February 18, 2013 a 6:40 pm
                                  • 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.

                                    Tech
                                    February 19, 2013 a 8:53 am
                                  • 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?

                                    Dmac
                                    February 18, 2013 a 10:21 pm
                                    • 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.

                                      Tech
                                      February 19, 2013 a 8:57 am
                                    • 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

                                      thanks

                                      Chohan
                                      February 23, 2013 a 3:27 am
                                      • 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.

                                        Tech
                                        February 25, 2013 a 9:34 am
                                      • Great tech support here!

                                        Betty
                                        March 14, 2013 a 6:48 am
                                        • 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!

                                          Autumn
                                          May 30, 2013 a 2:47 pm
                                          • You‘re Welcome~!

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

                                            Chuck
                                            May 30, 2013 a 1:13 pm
                                            • Yes they are! Follow this link:

                                              www.batterystuff.com/batteries/aa-aaa-9v-nimh/

                                              Jeremy Fear
                                              May 30, 2013 a 1:36 pm
                                            • 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.

                                              Dick
                                              April 20, 2013 a 11:37 am
                                              • We are glad you found it to be helpful! :)

                                                Jeremy Fear
                                                April 24, 2013 a 9:32 am
                                              • 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?

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

                                                  Jeremy Fear
                                                  May 21, 2013 a 11:49 am
                                                • Kodak Ni-MH Rechargeable Battery heat up while charging..is it a problem..plzz help
                                                  AbhinayD
                                                  May 21, 2013 a 5:36 am
                                                  • It may be. I would recomment contacting the manufacturer to find out the heat tolerance of those batteries, and measure the temperature accordingly.

                                                    Jeremy Fear
                                                    May 21, 2013 a 11:49 am
                                                  • 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

                                                    Daveboy
                                                    June 21, 2013 a 3:50 am
                                                    • thaaaaanks

                                                      Adel Salem
                                                      June 22, 2013 a 7:49 am
                                                      • Really clear & helpful

                                                        Fast Robert
                                                        July 25, 2013 a 10:50 pm
                                                        • 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.

                                                          Ashton Grave
                                                          August 6, 2013 a 10:52 pm
                                                          • 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.

                                                            JT
                                                            August 9, 2013 a 9:59 am
                                                            • 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

                                                              R Woods
                                                              August 14, 2013 a 4:34 pm
                                                              • 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)?

                                                                Thanks.

                                                                Jim O
                                                                November 29, 2013 a 3:34 pm
                                                                • 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!

                                                                  Kurt
                                                                  February 16, 2014 a 11:47 am
                                                                  • 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?

                                                                    Steve
                                                                    March 21, 2014 a 4:23 pm
                                                                    • Wow! Very helpful, thank You!!!

                                                                      Vladan
                                                                      March 26, 2014 a 8:18 am
                                                                      • 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?

                                                                        Effem
                                                                        March 30, 2014 a 12:08 am
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