Build Your Own Arcade Controls Forum
Main => Everything Else => Topic started by: RayB on September 26, 2010, 04:05:21 pm
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Is it normal for rechargable batteries (AA) to just lose power after a while even if not in a device?
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yes
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For NiMH:
The self-discharge is 5–10% on the first day and stabilizes around 0.5–1% per day at room temperature.
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Yup, very common. In fact, it's worse on the newer batteries. There's something of a trade-off between absolute capacity (mAh rating) and self-discharge rate for Ni-MH chemistries. Since Ni-MH batteries are sold mostly based upon the capacity figure, development has been driven in that direction at the expense of self-discharge for the stuff you normally see advertised and at retail.
It's possible to make the trade-off the other way. These are made and sold under various trade names with "Infinium" and "eneloop" being some of the more common. They have slightly (~10%, typically) lower capacity than the top-of-the-line batteries you normally see, and they cost a little more, but they'll hold most of their charge for weeks or even months. There's a Wikipedia article (http://en.wikipedia.org/wiki/Low_self-discharge_NiMH_battery) that lists some of the common trade names for these.
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The Sanyo Eneloops keep a decent charge for months on the shelf. They won't be full capacity but enough to still be usable while you're charging another set. I think there's some Sony's out there that are rebranded eneloops .
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Well then, lesson learned. Don't buy Energizers.