Posts tagged ‘battery’

KWeld spot welder

I recently bought Kweld spot welder kit for all battery welding purposes. The old, transformer welder was not good and welds were not consistent and reliable. Worst issue with transformer welder was inability to weld thicker metal strips (0,3mm Ni).

The Kweld came with everything needed to start welding except power supply source. They offer supercap bank with charger or recommend some RC batteries. I had niether. The most suitable battery pack I have was 3S1P LiFePo pack with internal resistance of 5mΩ. Unfortuantely such source is not OK for kWeld.

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2S LiPo Battery pack

IMGP3715.jpg2S Battery pack is very useful. It can be used to supply 5V electronic circuit without DC/DC. With help of a simple boost a 2S battery can drive 3 power LED lamp with reasonable currents. Etc…

Let’s see what is required for reliable, safe lithium polymer batter pack with two serially connected cells (2S LiPo battery pack).

Obviouslly, at least two cells are needed. Unfortunately, LiPo cells are very dangerous if used over specified limits. Most dificult is maximum cell voltage during charge. If cells are aexposed to voltages above 4,2V they can burn, but not at the charging, this could happen at any time after charging.  The absolute maximum charging voltage is 4.25V per cell. To avoid burning down the house and other troubles, a battery protection circuit board (PCB) is a must with LiPo cells.

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