Battery Nimh

Posted on | September 5, 2010 | 2 Comments

Battery Nimh

Does the life of a NiMH battery reduce if kept uncharged (unpacked)? How long does it last unpacked?

Panasonic P-P511/P-H402 3.6V 1000 mAh battery made in 06-2005, unpacked. Will it last long like a fresh piece? Is there an expiry date without even charging a new battery?

My experience with Li ion battery (the type that goes into laptops) is that there is some degradation even if the battery is unused, but the degradation is slow. I have used a new battery that sat in a box for 3 years, and after a full charge, the battery meter on the computer said that the remaining battery life was about 70% of what I would expect out of a fresh new battery of the same type and size.

For NiMH, the article below says that these batteries have a lifetime of 3 years if unused, and that the drop is irreversible. It doesn't show the drop curve though: http://batteryuniversity.com/partone-19.htm . I guess your battery has one more year left in it.

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Overcharging AA NiMH Batteries with 12V battery?

I have a digital security camera that runs on 6 AA batteries, battery life is an issue so the the manufacturer also sells a 12V solar panel that can be hooked into the camera and recommends using AA rechargables. I would like to hook-up a 12Vbattery because the solar panel won't work for me. Will the 12V over charge and burn out the AA batteries? Thanks.

Standard AA rechargeable batteries are rated at 1.4VDC each. If they are wired in series to power the device, the total DC voltage available to the device is 8.4 volts (1.4V x 6).
The camera should have a built-in power control circuit to regulate the voltage. If the manufacturer is selling a 12v solar panel designed for the camera, the voltage should not be a problem. Rechargeable batteries have a certain number of cells, which determine the rated output voltage. The batteries will not be overcharged by the solar panel.

[Technical Note: The difference in potential between the charging device (in this case the solar panel output of 12V) and the battery load (8.4V assumed) is approximately 3.6 volts. That is the actual charging potential.]

The reason why AA rechargeable batteries are recommended is because non-rechargeable batteries are not designed to be recharged. Thus non-rechargeable batteries can be overcharged, which can result in overheating and leaking. This would damage the device. If you are going to use the solar panel - get AA rechargeable batteries (either NiMH or Li-ION).

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