Posted: 8/31/2009 5:19:59 AM EDT
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Quick question. I have a 7.5v battery that needs charging. The standard charger is 8.4v at 600mAh. but all I can replace it with is either a 9v charger at 300 or 450mAh. Can I get by using either of the chargers, or will I run the risk of ruining the battery?
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http://www.batteryuniversity.com/partone-12.htm What happens if a battery is inadvertently overcharged? lithium-ion is designed to operate safely within their normal operating voltage but become unstable if charged to higher voltages. When charging above 4.30V, the cell causes plating of metallic lithium on the anode; the cathode material becomes an oxidizing agent, loses stability and releases oxygen. Overcharging causes the cell to heat up. If left unattended, the cell could vent with flame. I haven't ever tried using a Li-Ion battery with a charger other than the one it came with, but according to this, it looks like it's bad juju. I'd take the time to get the right charger. |
| The battery is for a Samsung camcorder. Here's the interesting part. My Sony camcorder uses a 7.2v battery, and the charger for it is a 8.4v 1.7a unit. I was able to rig it to charge the battery by running two wires from the charger. However, to do this I have to remove the battery and actually tape the wires to the battery. If I can figure out the requirements for the battery, I can actually fab up a charger to use directly through the camcorder itself (via the pin in the back). |
| Your battery has two Li cells in it, each is nominally 3.7V, so battery nominal voltage is 7.4V, but each cell at 100 percent charge will be 4.2V, hence 8.4V output on the charger, as it flows a constant current (for my camera, a .9 C current) and then a constant voltage at the top of the range. A charger that you buy that is not for that voltage will overvoltage it and destroy the battery, possibly causing other damage when that happens. You are playing with fire if you try that. |