Quote:
Originally Posted by jsr
Yeah, I opened up the hardcase on every pack and resoldered the cells. After doing so, most of them continue to re-open under any load near their "100A" rating. Since then, I use them for setups that don't draw as much current, but I've had them open on a 60A setup (that never got past just warm, so I doubt it was even drawing 60A). The tabs on the cells does not allow solder to wet. This was the case when they were first put together and also when I resoldered them. I even sanded down one of the cell tabs that didn't wet well to get clean metal and it still wouldn't take solder. Because the tabs don't wet solder very well, most of the joints that opened were because the factory knew this and all they did was blob enough solder so that it made a pressure joint against the tab (meaning the solder blob just pressed against the cell tab to make electrical contact). Any mechanical vibration (like in a RC truck) or heavy thermal stress (like big current draws heating up a crappy high-resistance electrical connection) would easily open a pressure connection. I took a picture of the solder joint before, but am too lazy to find it. I posted it on RCU or somewhere.
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Thats because your not using the right type of solder and I'm gonna guess your not using flux as well...