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After having burned a small hole in my finger, I'm trying to figure out why exactly the Micro-Lipo charger heated up instantly.

I am using the Adafruit Micro-Lipo charger

which has the following specs:

3.7V/4.2V LiPoly/LiIon 100mA charge rate default Short jumper for 500mA

I had connected a 3.7V 1200mAh battery to the terminals where the entire board heated up instantly. The battery is an uxcell 603450.

Was this because the mAh rating on the battery was way too high? There was no power source connected to the MicroUSB port on the charger.

If it is the size of the battery, how do I calculate what size charger I need in order to charge 3 of the 3.7V 1200mAh batteries wired in a series?

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  • \$\begingroup\$ Do you have a datasheet or part number for the cells you were using? Did the charger overheat and let the smoke out? or did it just heat up? \$\endgroup\$ – VBwhatnow Feb 25 at 17:54
  • \$\begingroup\$ @VBwhatnow Added in a link to the battery I'm using. the charger went from regular room temperature to too hot to touch in a split second; I was mistakenly holding it. It hadn't started smoking yet, but there was a burning smell. The battery was on there for about 20 seconds before I found some pliers to disconnect it. \$\endgroup\$ – Brian Feb 25 at 18:00
  • \$\begingroup\$ Are you certain that the red and black wires were the right way round? \$\endgroup\$ – Finbarr Feb 25 at 18:22
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    \$\begingroup\$ "If you are soldering on a JST cable or using a non-Adafruit battery check the polarity of the wires going into the battery port. A backwards battery can destroy the charger!" As you're using a non-Adafruit battery, did you actually check or just assume it must be right? \$\endgroup\$ – Finbarr Feb 25 at 19:11
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    \$\begingroup\$ You should probably re-think the whole project - you cannot use these to charge series connected cells as you state as your goal. Nor can you use three of them, unless their power sources are fully isolated (and even that would be a very bad idea) \$\endgroup\$ – Chris Stratton Feb 26 at 16:20
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Given the Keying of the connector on the battery and the keying of the connector of the Adafruit Micro-Lipo charge; Finbar is probably right, you appear to have connected the battery with the wrong polarity.

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