Cor van de Water via EV wrote:
Why don't you try to connect the two first and see if there is a
problem that you want to solve, instead of first building a solution and
then finding out that it is not needed at all?
That's a good idea. If these are big low-resistance AGMs at
significantly different states of charge, the peak current could be
formidable (over 100 amps). But if they are smaller flooded cells, or
known to be pretty close in state of charge, then the peak current won't
be all that bad.
Examples:
1. My old ComutaVan had a contactor controller. It routinely switched
its 6v golf cart batteries in series/parallel combinations for motor
speed control. This tended to keep the battery state of charge
relatively close. The current between batteries when switching them was
only 10-20 amps.
2. My VW Eurovan had a 12v flooded starting battery, and a 12v
deep-cycle "house" battery. When parked, you could run lights, radio,
etc. off the "house" battery for overnight camping. When you started the
ICE the next morning, a solenoid closed to switch them *directly* in
parallel. There was a 100 amp fuse; but it never blew. When the house
battery was deeply discharged, the peak current was on the order of
50-100 amps. It fell under 25 amps in just a few minutes.
3. For a few years, we provided our BEST kid-EV teams with two
low-resistance 12v 40ah AGMs. For safety, each had a 30 amp circuit
breaker permanently attached. One team rigged up series/parallel
switches so they could get 12v or 24v to their motor. They found that if
they ran on one battery until is was half-discharged, and then tried to
switch it in parallel with its fully charged twin, both circuit breakers
INSTANTLY tripped. These were thermal breakers that normally take a
minute or more to trip at rated current, so the peak current was
probably well over 100 amps.
--
"IC chip performance doubles every 18 months." -- Moore's law
"The speed of software halves every 18 months." -- Gates' law
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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