The Engineering Notebooks by Forrest Mims (sold by Radioshack originally) are a great resource for simple circuits like this. You can take your choice of method. A comparator circuit occurs to me first. It will change its output based on the difference between two voltage signals. When the target voltage and actual voltage are the same the difference is zero so you get no charging current. Of course this has to be interfaced with the power side.
You can use digital means as well as transistor logic (TTL). You can latch them, or make set/reset circuits, all with very mall low power circuits. On Tue, Jun 23, 2015 at 10:45 PM, EVDL Administrator via EV < ev@lists.evdl.org> wrote: > 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) > > -- To invent, you need a good imagination and a pile of junk. Thomas A. Edison <http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 585-6737 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150623/82372534/attachment.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)
