Quote:
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Originally Posted by A4DTM
...i know you're always supposed to monitor the chargers.. but if a cell blew up, what could i do anyways? i've got it in a lipo-sack sitting on a big piece of metal..
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Well, you're right; if it's gonna puff, it's gonna puff and there's not much you can do about that. But if you're there monitoring them, you can stop the charge before the cells go from puff to flame. Using a lipo sack and on top of something non-flammable simply
mitigates the risk, it doesn't
eliminate it.
If charge time is important, then I would either get a single supply capable of about 25A, or two supplies each capable of 12-15A. You don't want to pull the max current a supply can supposedly generate because:
1) It reduces the life of the devices running at their max.
2) Power supplies are rated to supply a certain current at usually 25*C - but the inside of a PS is rarely 25*C and there is a derating curve.
3) When drawing the max current (or close) a supply can provide will cause the output voltage to drop. When this happens, the current has to increase to compensate which then causes the voltage to drop further.
You can make the power supply a little more stable on the 12v line by loading the 5v and/or 3.3v line(s) with about 1-2A. All supplies are switching units and the circuitry usually measures the current on one of these other lines to provide feedback for the regulator to adjust the voltage on all the lines accordingly. The reason for this is because these power supplies are meant to be used in computers where all lines are bing used in a somewhat equal proportion. So, the circuit assumes that heavier current on one line will most likely be drawn on the other lines. Since you aren't using the other lines, the circuit thinks you aren't using much power on the 12v line either. And since it doesn't measure the 12v line specifically, it has no way of knowing. I hope all that made sense and I didn't give you useless info. :)