On 31 May 2015 at 22:48, Lee Hart via EV wrote: > In this case, the ComutaCar charger is *not* voltage regulated, nor > current limited, nor is there any shut-off timer. It is nothing but a > big transformer and rectifier.
I had a 1980 C-car. Its charger was pretty crude, but it was a little more than this. I believe the term for its charge control is "cycle dropping." It charges the battery to an OCV threshold, then shuts off and waits for the battery voltage to fall to some value a little below this voltage (I don't recall the hysterisis). Then it turns on again until the voltage reaches the threshold. This cycle repeats, with the long-term average current dropping, for many hours. As the battery approaches full, the duty cycle gets very short, eventually reaching a second or less. Here is the circuit : http://www.evdl.org/docs/c_car_charger.jpg In the 1980s I saw an absolutely identical circuit in a EE reference design book (don't recall the title or author). This is the same "algorithm" used by many cheap automotive battery chargers. EVDL old-timers may recall that the "blinky" chargers, made by Cliplight of Canada and sold with Zap ebikes, worked this way. Most of the consumer chargers add some kind of protection against reverse polarity. As for the need for a BMS, we don't know anything about Gail's "adoptee," but I would caution against assuming that he can (or wants to) invest significant amounts of time in EV maintenance. We want this person to have a good experience with his C-car. "Bottom balancing" may work fine for careful hobbyists. (I was going to say "careful hobbyists like us," but I know myself well enough to know that I'd wreck the battery if I tried it.) The average person just wants to drive the car, not babysit it. The era of regular automotive self maintenance is just about over. When I was a kid, my father was out in the driveway and under the hood of his '56 Chevy nearly every Saturday. He checked and changed the oil, checked and changed the coolant, and did filter changes and basic tuneups (plugs, points, condenser; sometimes rotor and cap). Who does that stuff today? Heck, I know some folks who have their dealers or mechanics fill the windshield washer reservor! Few auto owners pop the hood weekly or even monthly. Many never open it at all. > A BMS should be looked at like the circuit breakers in your house. An excellent analogy! 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)
