I have seen drivers charge their pack from another pack.
The first instance was when I heard of a couple in the East SF Bay EAA
Chapter, the Cornell's, who both drove EVs. Talk about getting the most
out of the $ they spent on a pack, when a pack was replaced because its
range did not suit their needs, the batteries that still had life in
them were stored in the garage, and kept charged from the solar array on
their roof (this was at a time when there were no solar incentives, and
the Cornell's were way ahead of everyone else. Their roof solar would be
thought of as common place by today's standards).
When one of them got home, they would recharge their EV off the older
pack which had been recharged from solar electrons. The current they
used to recharge their pack was low, so I would not call it a dump
charge. At that time, a dump charge was what the racers were doing at
the track with high currents (like level-3 power), to get back out to
race on the track (APS racing).
The other experience was at high current levels, so you could call it a
dump charge of sorts. In both cases, the effort to transfer the power
from one pack to the other was a manual one, where the human brain was
the smart charger. They each used a source pack that was at an
incrementally higher voltage (higher than a destination pack voltage).
The example is when I hung out with John Wayland at a Sacramento Raceway
nedra.com EVent. His White Zombie at the time I believe had the smaller
Jonson Controls agms. His older pack that used to be in his EV were made
up of Optima yellow top agms. When he came in to his pit location after
doing his run, he would measure his pack voltage, and match that plus
one more 12V agm. Then connect the slightly higher voltage old pack to
his EV's partially spent pack. As the dump current decreased, he would
add another 12 agm to bump up the current. He knew from experience when
to do this so as to not push too much dump current, and to not waste
time on a lower, slower dump current.
When John's EV pack had reached the finishing voltage, he pushed/goosed
it a little, forcing a higher than normal finishing current into his
EV's pack. This caused his EV's agm pack to steam some of the
electrolyte. John said he did this on purpose because his hot pack
performed better (one could like that thinking: prematurely
aging/destroying his EV's agm pack just so he can get a better race
time, to what the ice heads to when they push their ice beyond
red-line). After he left to go get in line to race again, he had a
genset pushing power into the old Optima set of batteries that was in
his support vehicle.
I've heard of drivers of today using a controller to push the power from
one pack to another. IT still would require a human to incrementally
bump the current up as the pack charged, but no batteries had to be
added, you could start out by using the highest source pack voltage.
{brucedp.150m.com}
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On Sat, Apr 19, 2014, at 02:12 PM, Dan Baker wrote:
> Hello fellow Evlist users,
> I have question around charging the battery pack on an EV from a larger
> pack of batteries, same voltage. I'm looking to build a stationary solar
> array (48v) and charging 12 x 12 volt 133 amp/hr sealed lead acid
> batteries, 4 batteries per bank These are retired but gently used UPS
> batteries and I will have about 1200 watts in solar going into a
> Morningstar 45 amp solar controller. I would like to be able to charge
> my
> EV boat pack (http://www.evalbum.com/4767) from this pack, UPS batteries
> again, but 4 x 12 volt AGM 133 amp/hr.
> My questions for the list: how do I transfer the charge from the solar
> bank to the EV pack? Can I just use a charge cable directly and the two
> banks will equalize? Or would I need to use a charge controller? I
> have
> another 45 amp solar controller I could hook from the main battery pack
> to
> the EV pack but I fear the input amps would exceed it? I remember a
> while
> back someone mentioned they were charging a lawnmower from a truck pack,
> wish I could find more info on this ...
-
--
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love email again
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