short lived UPS system [RE-wrenches]

[Christopher Freitas - OutBack Power]

I think the poor life of vented batteries in the Trace SW UPS systems 
can be attributed to the continuous charging of the batteries at the 
float voltage level.  I have observed that the water consumption of the 
batteries increases with age and then gets even worse quickly - so the 
users get on a certain schedule (if they ever do it) and then they still 
end up with dried out batteries. 

The solution here is to NOT float charge the batteries continuously - 
but to give them a rest period each day when the inverter is not seliing 
power back to the utility grid.  This also improves the perfomance of 
the system by reducing the losses at night.  

This capability should have been implemented in the SW series years ago 
- but it still isn't even today.  There is a automatic control box sort 
of available from Darren of solarhackers.com that automatically switches 
the inverter from SELL mode during the day to SILENT mode at night - but 
additional hardware adds cost and should not be required.  The upcoming 
OutBack grid-tied software includes this "silent-sell" capability 
inherently without any additional hardware required.  

So - I think using flooded cells with continuous charging is the real 
source of the failure.  I also advise using sealed AGM batteries for thi 
stype of application - but also think using an inverter system that 
continuously floats them is asking for trouble.  

Christopher Freitas
OutBack Power Systems, Inc.
cfreitas at outbackpower.com  www.outbackpower.com
Tel 360 435 6030  Arlington WA USA

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