Maintenance Tips for Rechargeable Batteries

I found a good deal on some Maha Powerex 2700mAh NiMH AA batteries on Amazon.com, and it occurred to me that I should write an article on good battery management to get the most out of your battery investment. I highly recommend these specific batteries to photographers because they are pretty much the most powerful AA batteries you can get for high energy devices like external flash. They won’t hold an 85%+ charge after sitting for a year on a shelf like some of the Maha Imedions and Sanyo Eneloops, but I don’t buy batteries to sit in my camera bag for months on end unused! 2700mAh will last a long time under heavy use for bright LED flashlights, external flash, kid’s toys with motors, etc. What’s particularly amazing is the speed an external flash will recycle at full power, typically around 3 seconds on my Nikon SB-900 with freshly charged batteries. Most impressive is that even after 500 full power pops it still averages around 7 seconds when most other batteries average 16-20 seconds—that’s a disaster at an event like a wedding! At normal power levels (fill flash) the flash will keep up with 9 burst bracketed shots at 8fps without skipping a frame. At half power (dominate light source in dim light) it will hit 3-4 frames, especially if I lower my shooting speed to 4fps. Usually my flash will overheat long before I reach 100 full power shots (maybe around 50-60?), and even at quarter power it’s difficult to hit 100 shots in very quick succession. However the batteries are still only slightly warm to the touch when they are removed and the overheating issue is a well-known problem on the Nikon SB-900 flash. Someday I will get an updated SB-910 as my primary flash to resolve the overheating issue, although I wish Nikon had done a product recall or firmware update instead of releasing a new model to resolve it. Sigh…

If you would like to see a very thorough test done on several common rechargeable batteries I highly recommend this link: http://photography-on-the.net/forum/showthread.php?t=677074 The Powerex 2700mAh comes out on top for every test that really matters for photographers.

So, you've invested a bit in some good NiMH rechargeable batteries (any brand or model), what are some good practices to maintain them and keep them in good shape for years to come?

1) First, I would recommend a very good charger. I use a Maha MH-C808M to charge not only AA, but also AAA, C, and D sized batteries, which is very useful in my household with four kids! Maha MH-C9000 is a good portable charger for AA/AAA on the road. Not every battery charger will properly charge high capacity batteries without overcharging or undercharging them, so see what your charger is capable of before charging 2000mAh+ AA batteries in it. I especially recommend a charger that has independent channels to charge each battery individually instead of in pairs. Not every battery charges and discharges at the same rate (even if they are the same brand/model), and even if you label them and always keep them in pairs (like I used to with my old NiCd’s) over time you will find you are only getting about a quarter of life out of your batteries as they will only charge as much as your strongest battery and only supply power for as long as your weakest battery. Eventually one will only charge to about 20% and the other one will only drain to 80%, giving you about 20% battery life. Splitting up pairs and swapping them around quickly makes it even worse, especially in devices that use an odd number of batteries. If you have a bunch of old NiMH batteries in this state, you can probably recover them with a new charger and use them for lighter duty like remote controls around the house as I’ll show you shortly.

2) Second, I recommend a charger that can do rapid charge when you really need it at a wedding or other event, or decide to take a spur of the moment trip and have two hours to top off a bunch of batteries. Be aware that older and lower capacity (under 2000mAh for AA) batteries can be permanently damaged or even explode with rapid mode charging, so only use it on your premium batteries and only when you really need to as the higher heat level will shorten the overall lifetime of your batteries. Use the longer soft charge as much as possible to get the longest lifespan and highest charge out of your batteries. But for critical events and unplanned photo shoots, rapid mode has saved many a day for me!

3) Third, I recommend a charger that can do deep conditioning. I've recovered many of my older batteries by deep-discharging and recharging them. I use the older batteries in low power devices now like remote controls and such around the house. I've been able to recover batteries for other people too. Just don’t expect a battery that has not been properly maintained to deliver the same performance it used to. Even well-cared for batteries will eventually wear out with age and use. When even a conditioning charge no longer works on a battery, it’s time toss it.

4) Fourth, it’s a very good practice to run a conditioning charge on all your batteries after about ten normal or soft charges. This will keep your batteries in top condition for years to come and hundreds (if not thousands) of charges. To keep track, I wrap a piece of clear scotch tape around one end of the battery and mark a little tick with a permanent marker for every charge. Once I've hit ten, I do a conditioning charge and put on a fresh piece of clear tape, starting all over. Be careful not to overlap the tape if you don’t want to change the thickness of the battery for very tight tolerances like Mini Maglites. You can see my method in this photo.

5) Lastly, I rotate my batteries. I tend to grab the batteries with the least number of tick marks to make sure I wear them all evenly. I also split them up and swap them around between devices when I recharge them so the same 2, 3, or 4 batteries won’t keep getting used in the same device under the same usage conditions. So throughout the lifetime of a single battery it will get used in high current and low current devices, that prevents some batteries from wearing out faster than others. When they start taking a long time to condition charge (usually after several years of use for me) I permanently mark them on the other end of the battery and start using them exclusively in low power devices such as remote controls, since they no longer hold up to the demands of my flash on critical photo shoots. I've still gotten several more years of use from old batteries in low power devices though, some of my oldest NiMH batteries are over 15 years old!

These practices have let me get incredibly long life and great performance out of all my NiMH rechargeable batteries. If you have any tips or suggestions, please share them in the comments for others. If this was useful to you, feel free to re-share it or comment below!

Happy shooting!