charge voltage [RE-wrenches]

[Richard Perez, Home Power magazine]

<x-flowed>Hello Kurt

PV are essentially constant current devices, so just select a module 
(regardless of voltage) which has the appropriate current rating for 
recharging the alkaline cells. If the module has say C/5 rate or 
better into the battery, then it will overcharge the battery in a 
single day--then you need some form of regulation if unattended.

Straight voltage regulation is dicey--the cells need to come up to 
over 1.6 VDC per series connected cell and then drop back to a C/20 
rate or less for floating. I imagine that a circuit could be made to 
do this. Say an LM723 which after the cells reach say 1.64 VDC each 
would enable a LM317 configured as a constant current source.

Richard


At 18:06 -0800 10/29/00, Kurt Nelson, SunWise wrote:
>Richard Perez, Home Power magazine wrote:
>  >
>  > Hello Kurt
>  >
>  > Sintered plate alkaline cells are floated by current not voltage. Use
>  > the C/20 rate (50 mA for a 500 mA-hr cell) and you can float them for
>  > days.
>  >
>  > Hey Richard and thanks.  I realize current is the way to float, I 
>guess I should have mentioned that I was attempting to make a 
>"match" between the number of 150 mA PV cells in series with three 
>AA ni-cad batteries in series (3.6 V, 600mA).  I say "match" because 
>I was hoping to do an unregulated charge with this larger panel and 
>look to the power curve of the panel to due some self regulation.  I 
>have a bunch of cordless phone battery packs and a bunch of 8 and 10 
>cell encapsulated hobby panels.  I've been messing around with them 
>and some white LED's.  The LED's regulated circuit can see anything 
>from 3-14VDC.  Would the battery pack be over-charged if the pack 
>came up to near OCV of the 10 cell panel (5V)?  Seems like the 4 
>volts of the 8 cell panel would be way lite?  I realize this is not 
>an ideal way to charge such a battery, but thought it might work 
>out, especially with NiMH, which would not have as high a tendency 
>to develop memory?
>
>I should have explained better, but maybe the answer is the same.  Not a
>good way to charge?
>
>Thanks, Kurt

------------------------------------
Richard Pérez
Home Power
PO Box 520, Ashland, OR 97520  USA
Tele: 530-475-3179
FAX: 530-475-0836
Subscriptions: 800-707-6585
mailto:richard.perez at homepower.com
Web: http://www.homepower.com

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