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Old 01-20-2009, 10:38 PM   #19 (permalink)
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Originally Posted by MazdaMatt View Post
I did some reading on chargers and found the wikipedia page that explained that a "simple" charger either uses constant current or constant voltage, but may not be the most efficient... would it be reasonable to string 9 batteries in series and simply apply a wave-rectified, capacitor-smoothed wall outlet voltage across them? Sounds absolutely insane to me. I'm just thinking, if I had a 12 battery pack and had a dpdt switch that could make them either 2 parallel strings of 6 or one series string of 12 (not a difficult switch to imagine), then i could use a very gentle step-down transformer and a couple big capacitors to charge them...

again... sounds crazy to me, but that's what i gathered from a "simple charger" description.
I think that would be fine. You could have it shut off a tiny bit early when all the weirdness starts (the bulk charging is done, and hydrogen gassing might begin in earnest). Lead Acid is very forgiving during the bulk charging phase, or so I hear. I don't know what I'm talking about!

Actually, I think that's a really good idea. Charge 2 72v strings if you have a 144v pack. Then you could do without a transformer in the charger, and you could smart charge it with a micro-controller and PWM setup, just turned down a bit, since the rectified DC voltage would be around 160 or 165 (just a little bit less than the peak of about 170v.), and you could just run the pwm at 50% to get an average voltage in the 72v charging range.

I checked yesterday, and with 11 of my 200v ripple current capacitors, at 24v through the motor, there was a ripple voltage of 0.1v. I bet it wouldn't be that much ripple from the wall. I have no idea though. I need to test some of that crap out. haha!
kits and boards

Last edited by MPaulHolmes; 01-21-2009 at 12:56 AM..
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