I get questions all the time from people using NiMH Rechargeable Batteries that don’t last very long or that don’t seem to put out full power. The obvious question is whether there is something is wrong with the batteries, the charger, or both. These batteries are pretty expensive and it can be really annoying when they don’t do the job they are needed for.
Unfortunately, rechargeable batteries continually lose some of their power in a process called self-discharge. This process occurs at different rates in every type of battery, and it occurs very quickly in standard NiMH batteries. In my experience they only hold enough charge for a few days before the reduced charge levels becomes obvious. When I try to use them in my Speedlite flashes I find that I really have to charge them the same day, or maybe the night before, if i want to get decent life out of them.
If you need your batteries to last longer then you need to get low self-discharge batteries (often marketed as Pre-Charged batteries), such as Sanyo Eneloops. I find that these batteries, even at only 2000 mAh, last far longer and are much more useful than any of my 2500 – 2900 mAh standard NiMH batteries. I now have enough of these batteries for use in all of my flashes plus a spare set for each flash as well. You can leave these in your camera bag for months and they only lose a small percentage of their power.
For more information and to learn about other brands of batteries, check out the Low Self Discharge NiMH Battery article over at Wikipedia.




