NiCad Batteries [RE-wrenches]

[Brad Bassett]

John,

My understanding of NiCd's is that they are not affected by staying less 
than fully charged like Pb acid batteries. Also, that they will charge 
up to about 90% of full at regular PV system voltage ie: 15 volts or 1.5 
v/cell with 10 cells. So my assumption is, without direct experience, 
that you just don't use the top 10% of the battery's capacity. I have 
also read that if held at a lower voltage, 1.5v/cell, given enough time 
it will eventually fully charge the battery. I've specified a few NiCd 
battery banks to northerly climes and have not had any negative feedback 
with this method, for what it's worth. It's been a number of years since 
these batteries went in and there was no way to equalize them either. 
Actually they were large enough that after 5 years they might be just 
about discharged for the first time. The system had about 3 years 
battery autonomy, they are being used for seasonal storage (smalll 
load). I wish I could do that! 

The problem with going to 9 cells in a 12 volt system is that the 
voltage can drop too low for the loads, 1.2 x 9 = 10.8v running voltage.

Brad


John Blittersdorf, Cent. VT Solar & Wind wrote:
> Jay,
>     I just learned about using 19 instead of 20 but the DR manual says 19 is 
>     
> OK  but this is a 12 V system with two strings of 10 and they say not to 
> go 
> to 9.  Anyone had luck sawing these batteries apart?  Looks like nicads 
> and 
> 12V systems are not compatible unless someone else has some ideas.  This 
> 
> system was set up with golf cart batteries originally and the owner took 
> it 
> upon herself to buy some used Nicads to get longer life.  Maybe I should 
> 
> trade with her my 8 Trojan L16's for her 20 nicads and keep the 20th one 
> for 
> a doorstop. 
> 
> Jeff W., this may be one of your customers as she lives only a few miles 
> from 
> you.  I got involved as she is a dear friend of one of my new employees 
> and I 
> had a repair to do nearby (another friend).  
> 
> John
> CVSolar
> 
> --
> [Non-text portions of this message have been removed]
> 
> 
> 



Brad Bassett
Schott Applied Power 
Tumwater, WA office
bsbassett at earthlink.net

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