I’ve been using NIMH rechargeable AA batteries in various digital products for roughly 10 years now, but I just learned something kind of significant today while perusing prices on Amazon.com. One of the reviewers pointed out that high battery capacity (typically 2500-2700 mAh nowadays) isn’t the only characteristic you’ll want to look at. The other thing to look for in a modern NIMH battery is a low self discharge rate. Many of the highest capacity brands like Energizer have a high self discharge rate and will quickly lose a large percentage of their charge over the course of a month even if not used. If you’re swapping and recharging them daily or weekly that’s probably not an issue, but if you’re using them in scenarios where the device will be used sporadically over a longer period of time you’re going to want a long self discharge rate.