Damon Henry wrote:
19 - 20 volts which is too high for the hairball input... so I need some way to make sure the hairball never sees my full charging voltage or too high of a surface voltage after charge.
Steve Clunn wrote:
Any great ideas out there? I am looking for something that is low to no cost, and fairly fool proof. I'm not sure what the actual upper limit is, but for safety sake I would like to set 15 volts as the absolute upper limit.
This is a classic application for a 3-terminal regulator IC. Just a few examples: uA78H12 (12v, 5amp, old), LM323 (5v, 3amp, cheap, needs resistors to set to 12v), LM1085 (12v, 3a, low dropout). I'd try the LM1085 as it has the lowest dropout voltage (can deliver 12v out with a 12.5v input).
You could also build a simple regulator with a power transistor, resistor, and zener diode. Use a 15v zener, and it won't drain a 12v battery, but will clamp the Hairball voltage at 15v - the transistor's Vbe; about 1.5v for a darlington power transistor, or about 13.5v.
-- Never doubt that the work of a small group of thoughtful, committed citizens can change the world. Indeed, it's the only thing that ever has! -- Margaret Mead -- Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
