[RE-wrenches] Xantrex XW / AGM Battery charging issue

[Kevin Pegg]

Hi Folks, 

Greetings from northern BC, Canada. 

I've got several dozen Xantrex XW off-grid systems out there (12 / 18 / 24 kW systems) that operate either entirely as cycle charge systems off generator, or just part of the year when renewables aren't sufficient in the northern latitudes. 

The vast majority of these systems are using various flooded batteries - flat plate, tubular, 2V, 6V, etc. In all those flooded applications the battery bank is performing as expected and all is good. 

There are a few sites that client was not going to maintain batteries so UnigyII AGM's were installed. Every one of those sites it's a constant issue keeping battery capacity up. We would typically band-aid this by periodically boost charging the weak cells with a dedicated 2V charger but it's very tedious and costly to do. One of these sites is in the high arctic, 2 days travel. 

UnigyII cells are installed and operated according to spec (voltage, temp). Battery charge settings as manufacturer specified, and used the trick of fooling the XW by lying about the battery capacity, which did make some improvements - in that the intervals to boost charge increases. But at the end of the day it just does not appear the XW is returning enough energy to the battery and over enough cycles it adds up to serious undercharge. 

We have other UnigyII sites with other inverters (SW or Outback) and they are performing as expected. 

I have heard though the grapevine the XW is known for this problem, and that others have had this same issue. I have also heard that there is updated firmware for the XW that improves the less than perfect battery charging algorithm currently in place but it won't be released. 

Anyone know of any fixes to this (other than ditching the XW)? 

Thanks, 

Kevin Pegg
Industrial / Commercial sales
EA Energy Alternatives Ltd. 
37471 Hwy 16 E
Smithers, BC Canada
250-846-9888
Http://www.EnergyAlternatives.ca