Steve Clunn via EV wrote:
I am working on some Golf Carts and portable 12V power packs that get used
sporadically and may sit for months without use.
I have contactor on one 12V and 36V that draws about 1 amp. The problem
is, if everything is happy, the Mini BMS Circuit keeps the contactor ON.
Which draws enough current, that at some point, will drain the battery down.
I am trying to come up with a way that the owner can walk away from this
system, and come back to it and have it ready to go without having to
switch switches OFF and ON.
Steve, could you elaborate a bit more on exactly what you need to do? My
impression is that you have a 36v pack, with a contactor to connect it
to its load. You don't want to have an on/off key switch; just hop in
and drive. But that would mean keeping the contactor on all the time,
which would run the pack dead?
The best I can think of is something like a seat switch. When no one is
sitting on it, the switch opens and turns the contactor off, which
removes all loads from the batteries. When someone sits on the seat, it
turns on the switch, which turns on the main contactor, and away you go.
Another possibility is that Albright (and others) make latching
contactors. There is a magnet as well as the solenoid coil. The magnet
is sized to hold the contactor on (once it is already on), but not
strong enough to pull it in (if it is already off). You then pulse the
coil with a positive pulse of current to turn it on, or a negative pulse
of current to turn it off. In both states, the continuous power
consumption is zero.
--
If you would not be forgotten
When your body's dead and rotten
Then write of great deeds worth the reading
Or do these great deeds, worth repeating.
-- Ben Franklin, from Poor Richard's Almanac
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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