Li-ion Camera / Cell Phone Battery Charge Adapter

If you have some Li-ion/Li-po cells from a cell phone or a camera laying around, but for some reason don’t have the fitting charging adapter (since they all have three pins, but in a different distance), you easily could build an adapter to charge the batteries through any charger supporting lithium batteries (never ever charge them with a charger which does not support lithium batteries!!).

Note: this only works for single cell Li batteries (you have a single cell battery if it states to have 3.7V).

Technically it is very simple how the cell has to be connected to your charger. The cells normally come with 3 pins, labeled as „+“, „-“ and „T“. Well „+“ goes to „+“ on the chargers output, and „-“ goes to „-„. Since we only have one cell, no balancing is needed. But whats about the „T“? Some say „T“ stands for temperature, and that a NTC is connected between „T“ and „-“ (you could measure that with a multimeter, it should be something about 10k). Some (cell phone) chargers use the NTC to avoid charging the battery when certain temperatures are detected (to cold, to hot). Assuming, a charger which is appropriate for the battery is used (I use the X-Peak 3 evo from Jamara), and that it is used indoor only, we could just ignore that pin.

So the only thing left, is coming up with an adapter to connect the battery to the charger. I build a simple adapter using a prototype board, some header pins. On the one side I placed header pins in a way, they connect to the „+“ and „-“ contacts of the battery. On the opposite side I also added some pins to hold the battery in place while charging.

To make it a little more handy, I added some standoffs. To connect to the evo, I took one of the cables that came with the evo, but had a plug on the one side which looked so strange, I was sure never to use that. This plug I cut off and soldered it to the header pins which contact „+“ and „-“ of the battery.

When I charged the battery for first time, it took about 2h@0.6A until the charger told it was finished. While charging, the battery did not even get warm.

To get an idea of how I build the adapter, see the pictures.

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