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How should I recharge a 7.4V battery?

I have a 7.4V rechargeable battery and I'm wondering what voltage I should be charging it with.
would 9V work?
Are there any general guidelines for recharging batteries?

Specs:
7.4V
1400 mAh
Lithium-ion
Was originally used in a NXT LEGO robot.

Thanks!
Ryan

Picture of How should I recharge a 7.4V battery?
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It is generally considered a bad idea to try to charge lithium batteries without the proper charger or a voltage/current limited power supply. If you get it wrong, lithium batteries are likely to be damaged, catch fire or in some cases explode.

If the original application is still able to charge the batteries, that is the best option. Otherwise, you should build or buy a suitable charger. While you are trying to charge them you should monitor the temperature to try to avoid any serious issues.
jensenr30 (author)  The Skinnerz1 year ago
thanks for the advice! I'm going to look up how to make battery chargers.
I'm guessing I'll want a resistor to limit the current.

Ryan
Make sure you find instructions for a Li-Po battery charger at the correct voltage, as attempting to use a charger designed for other battery types can be dangerous.
jensenr30 (author)  The Skinnerz1 year ago
Good point. I have measured my AA battery charger and it outputs roughly 3V.
Needless to say, this is not the right charger for the job.
No! Make sure the battery charger you are using is rated for Lithium ion (or li-ion). Just a plain old charger, while might work, could blow up your battery. I think you can buy chargers on ebay rated for a 7.4v for pretty cheap if you have $10 or so
jensenr30 (author)  astroboy9071 year ago
I said "this is not the right charger for the job." As in, I wasn't going to use it. did you just misread it or am I misunderstanding you?
Just emphasizing ;)
pfred21 year ago
Whatever happens post an article here and share your adventures with us! It looks to me like you already have one image.
jensenr30 (author)  pfred21 year ago
i will
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