[RE-wrenches] offgrid system question

[jay peltz]

Hi PHIL,

Although the batteries may indeed be bad, I would point out that the  
the AC unit is turning on probably when the sun is out, therefore the  
total load isn't all on the batteries.

And do we know they are XW inverters?

thanks,

jay
peltz power


On Aug 18, 2008, at 3:18 PM, Phil Undercuffler wrote:

> My .02 would be a close examination of the batteries, and a  
> realistic realignment of their expectations of their capacity.  12  
> sun extender sealed AGM batteries, 305 AH at 12 vdc, wired for 915  
> AH at 48 volt DC -- sounds like those are the PVX-2580.  They’re  
> only rated 305AH at the 120 hour rate.  If you’re hitting that bank  
> with a fast discharge rate (is 104 amps at 120v or 240?), you’ll do  
> better to consider the bank’s capacity at the 24 hour rate (258AH)  
> or even 1 or 2 hour rate ( 165 and 209 AH respectively).   
> Realistically, those three strings of batteries are really a 774,  
> 627 or even a 495 AH bank, depending on how fast you’re discharging  
> them.
>
>
>
> Make sure the batteries have temperature compensation on all  
> charging sources, and that the batteries are not exposed to high  
> temperatures.  All batteries are affected by temperature, but if  
> VRLA batteries are charged without temperature compensation when in  
> a hot environment they will lose electrolyte which cannot be  
> replaced.  Additionally, ensure all connections are good and tight,  
> and that the bank’s series and parallel connections are sized  
> adequately to handle the surge.
>
>
>
> Finally, check the LBCO settings on all the XW inverters.  I can’t  
> remember the default setting, but my memory was that it is a little  
> too high – especially when the battery bank is small and surge  
> loads are high.  I worked on a troubleshoot the other week where  
> the installer set the LBCO only a bit below the AGS Start DCV 30  
> second voltage, on an older battery bank of questionable capacity.   
> Unfortunately, the batteries bottomed out before the generator  
> could get started and the system shut down a couple times.
>
>
>
>
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