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Re: (ET) Found the problem with the charger
On 7/15/2012 1:23 PM, Robert Adsett wrote:
You're using the GE charger to charge a Li-Ion battery pack?
Sure, why not? It's currently charging a NiCD pack with no issues.
That's a dangerous route you're taking. Even with proper protection in
the pack. There is not proper protection in the charger for this use,
the voltage levels will be different, there's a good chance the current
levels will mismatch etc...
Oh foo. These are 20ah A123 pouch cells arranged in a 12 cell block with
solid aluminum interconnects. You can hit them with a lot of current and
they smile. Theoretically you can hit them with a lot of discharge
current and they should be happy too. This is going to be a test
platform for putting them into my car since the E20 pulls about the same
amount of current as a 300 volt car (albeit at a lower voltage).
Protecting them is a MiniBMS board rigged for 12 cells. Currently they
are wired with a relay such that if any battery goes above 3.6 volts or
below 2.7 volts it will trip off the relay. And sound an alarm. Beep.
My plan for the E15 was originally to put them up front on top of the
NiCDs, and wire the relay such that it will turn off the charger
(through the timer looping through the relay) and will turn off the
power to the control relay (through the fuse block) when power goes low.
Bonus would be to tie the BMS into the key switch so I can turn on and
off the BMS as a part of running the tractor, but this is supposed to be
temporary.
However I might just put it in the back of the tractor and use a 36 volt
contactor to isolate the battery as needed. We'll see next weekend since
I need to deal with other things today.
Technically a 12 cell lithium pack will have a max working voltage of
43.2 volts. The regulators come on at 3.5 volts per cell or 42 volts,
which is when the Elec Trak charger is tapering off anyway. So this
might work well :-) In any event the BMS and the relay/contactors will
keep it from burning the pack.
And if the pack does burn it might help provide additional welding on
the frame. :-)
Chris
Li batteries are much (much, much) more sensitive to charge conditions
than lead-acids. Even the LiFe varieties.
Robert