Re: (ET) Buck/boost for E20 charger....

[Steve Gaarder <gaarder ecovillage ithaca ny us>]

I have some of those cells as well.  Just finished putting 20 of them into
packs and doing a "commissioning charge".

Nicads, as I understand it, prefer a constant current charge; you can use
constant voltage, but the voltage to use varies with temperature.  Cell
voltage rises gradually during charging, and then rises much faster as
full charge is reached.  If you keep the charge going too long, the
voltage will drop again and the battery will overheat.

Also, I have heard that it's ok to parallel Nicads when discharging, but
that they should be charged *separately* rather than in parallel.

cheers,

Steve Gaarder

On Sun, 12 Jun 2005, Christopher Zach wrote:

> Ok, this is going to be interesting.
> 
> So I came into possession of approximately 300 SAFT NiCD cells. Each 
> cell is a BB600 form factor, and puts out 30-40ah at 1.2 volts. Flooded 
> cells.
> 
> That's the cool news. What I want to do is put these puppies into my E20 
> and get rid of the T105's. I think I can replace a T105 with 15 of these 
> cells (5 cells wide=6 volts, 3 ranks deep=110ah) and get a tractor that 
> will run full power in the summer, winter, etc for about 20 years per 
> pack.
> 
> Problem is charging them. The E20's charger ramps up to 45 volts IIRC, 
> is it possible to change the cap value and boost the voltage a bit 
> higher? NiCDs like around 1.6vpc, or 8 volts per 6 volt battery or 48 
> volts nominal. Add 2 volts to that for the battery control circuit I use 
> (the TI DQ series) and I would need the Elec-trak transformer to put out 
> a max of 50 volts.
> 
> SO any thoughts on getting that ferro-resonant transformer to have a 
> slightly higher secondary without rewinding it?
> 
> Chris
> 
> 
> 
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