Re: (ET) battery charger controller

[William Korthof <wkorthof earthlink net>]

>
>Well, it seems like there might be some interest. If there is anyone who 
>is 
>local enough to come by with some goodies to swap, they can have the 
>controller and/or the charger. And I can show them some of the other 
>accessories I have made as well. If not, I can ship it.  Then maybe they 
>can 
>report to the list how it worked out. I'm thinking that $50 would be 
>about 
>the price for a controller and solid state relay. But that's just a 
>guesstimate right now. It would take a few serious orders to make it 
>worth 
>laying out a board and having some made.
>I like 38V because that is about the voltage that a fully charged 36V 
>pack 
>will settle to with no load. That's 2.11 V/cell. Plenty of people have 
>recommended higher, but I like 38V. The circuit has a pot on it to set 
>the 
>voltage anywhere you like.

2.11 volts per cell?? That seems awfully low. 
I don't have the table in front of me, but that's seems a 
lot more typical of the ocv for an 50% *discharged* pack...
If you don't periodically do a vigorous, full charge, you 
can forget about loosing capacity from dissociation of the 
electrolyte, and *expect* to lose capacity from sulfation. 
During charge, I would not limit the voltage to less than 
2.18 vpc. Actually, I would reccomend typical charging to 
at least 2.33 vpc, up to 2.50 for periodic equalizing. 
The open circuit voltage after good charging should sit at 
at least 2.17 vpc. Just remember to add water occasionally... 

IMHO, Lead acid batteries like to be charged. Especially 
run-of-the-mill L-A batteries are very handicapped if they 
don't get fully charged. 

/wk

>Harry Landis
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