On 23 Jun 2015 at 10:48, damon henry via EV wrote: > Has anyone ever made a circuit to shut off a switch once a predetermined > voltage limit has been hit while charging.
I "designed" (as much as any non-EE can "design" a circuit) and built a charger like that for my 24v Electro-Ped back in the 1990s, but I can't find my schematic now. :-( I'll keep looking. IIRC, I used a basic "cycle dropping" design but added a latching relay. A cycle dropping charger (without my latch) is about as simple as automatic chargers get. When the battery's on-charge voltage reaches the target value, it turns on an SCR through a zener diode. That SCR pulls a power SCR's gate low, stopping the charge. the output of the charger's transformer/rectifier is pulsating DC, so the power SCR goes to zero 120 times per second. So normally, when the battery's surface voltage falls enough, the charger can turn on again. This charger-on-charger-off cycle repeats, with the duty cycle gradually shortening and the average charge current falling. The battery is fully charged when the average current falls to ~C20/50. The charger should shut off for good at that point, but most of these simple chargers don't. :-( (BTW, I'm pretty sure this is exactly how the original Rudman Regulators worked, except that they closed a shunt round the battery, rather than opening the charging circuit to it.) If you filtered the charger's DC, you probably wouldn't need the extra latching components -- but that would probably be more expensive. Lee Hart may have some further thoughts on this. He's good at finding simple, inexpensive, and elegant ways to charge batteries. ;-) Here's one cycle dropping charge circuit, as used in late Citicars and Comuta-cars. http://www.evdl.org/docs/c_car_charger.jpg I've seen similar circuits, mostly for 12v batteries, round the web at various "maker" sites. I hope this helps. David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ 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)
