brushless and A123 questions

[BrianG]

Oh, so it sounds like this zip charger is relying on the resistance from a long and smaller gauge wire to limit the current.

A better way would be to build a simple constant-current source using a high current transistor like a 2N3055 or similar. You'd still have to monitor the voltage (or add other circuits to do the cutoff), but this setup can be made to have an adjustable and constant current.

You could also use a regular NiMH charger since those are CC chargers. Still have to monitor the voltage.

When charging A123's, does the voltage dip at all at the end of the charge? If so, you could set the delta peak value of a NiMH charger to a really small value...

[zeropointbug]

Highflier, that really does make me nervous when I hear you using the 12v battery 'mod' as a charger, I have seen it be done, but I prefer some decent electronics.

Brian, the A123's don't dip at all, but instead anything over 3.8v/cell, the voltage takes off like a sky rocket. At that point will most likely be very damaged if allowed to go over 4.0v/cell. But I hear 4.0v/cell is actually doable with these things.

If you want to use JUST CC, then you could use 3.8v/cell and use roughly 10 amps or more per 1p configuration, and then terminate charge once voltage is reached... I believe this will get you 96% SOC.

[Finnster]

That method is called the "nuclear charge" as I've seen it. Yeah, basically the wire is to provide some small amt of resistance so its not quite a dead short. Like a CV charge w/ barely limited current. I saw a wattmeter graph of it, and some of the initial charging was like 40-50A+ but obviously tapered off towards completetion. The idea is you try to match the # of cells to the lead batt, ie for 10S you would hook up to a 3S lead batt, then cutoff before it overvolts. Some people were charging M1s in like 5min depending on current limiting.