[RE-wrenches] low voltage disconnect

[Solar Plexus]

Wrenches.

	I have a customer with a stand-alone system with an XW inverter, XW  
controller,  pole mounted array of four 235-watt panels, and 4 of the  
8D gel batteries.   He uses the system mostly on weekends.
	Winter came, the solar array  was still set at about 30°,  a  
snowstorm covered  the panels while no one was there, and 4 days  
later the battery voltage was 6.
The week-end use had been substantial, so I assume the batteries were  
low prior to the snowstorm.  With no solar coming in, and loads still  
on, the battery voltage presumably went to Low Battery Cut Out   
voltage of 44 before the inverter disconnected  the AC loads.  With  
the AC loads disconnected, and no DC loads in the system, what caused  
the battery voltage to go to 6?
	 I assume the XW controller used 2.5 watts continuous or 60 watt-hrs  
per day as battery voltage went from  44 volts to 10 volts when the  
controller would have shut off completely.  What happens with the  
inverter when the battery goes below 44 volts?   Does the inverter  
shut off and there is no more draw on the batteries, or does the  
inverter continue to draw the no-load draw of 28 watts, or does the  
inverter draw the search-load draw of 8 watts?  At what voltage does  
the inverter stop drawing power?
	At 44 volts, the battery is presumed to be pretty dead. How many amp- 
hours are available in a 100 amp-hour 48v battery  (4 12-v batteries  
in series) while drawing the voltage from  44 volts and 6 volts?  Is  
there anything there or will the voltage just drop from 44 to 6 with  
very little power draw?
	The Low Voltage Disconnect is set for 44 volts,  but if the inverter  
itself does not shut off, then the practical low voltage becomes the  
voltage the inverter stops working at.  To protect the batteries, is  
there any advantage to limiting the low voltage to 44 volts as  
opposed to 6 volts.  If so, is there some way to have the inverter  
shut itself off at  low voltage?

We have had this same thing happen with an Outback inverter, again  
taking the batteries to near zero.  Is there any way that either the  
Outback or Sunny Island would operate differently than described above?

Looking forward to  any comments on these issues.

Thank you.

Lee  Tavenner
Solar Plexus
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