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. Phil Undercuffler Director, Battery-based and Off-grid Conergy Sales & Systems, Americas Our World Is Full of Energy 1730 Camino Carlos Rey Suite 103 Santa Fe, NM 87507 [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> Direct | 505.216.3841 Toll Free | 888.396.6611 x4841 Fax | 505.473.3830 www.conergy.us <http://www.conergy.us/> ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Max Balchowsky Sent: Monday, August 18, 2008 2:01 PM To: RE-wrenches Subject: Re: [RE-wrenches] offgrid system question Dear wrenches, going to look at a system installed by others and would like some input from some of you with more off grid experience than I have ( 4 systems over the years). the system was put on a new home - off grid 20 sharp ND123UJF panels 4 modules in series - 5 parrallel strings, 2460 total array dc voltage. mppt 60-150 charge controller, 12 sun extender sealed AGM batteries, 305 AH at 12 vdc, wired for 915 AH at 48 volt DC. The system is tripping off when the AC unit trys to start - AC is comfortmaker 3.5 ton 13 seer. They say start up inrush is 104 amps (sounds high to me) and they put a DST 10 soft start on the unit (I think that's just a big capacitor). I haven't been on site yet but it sounds to me that they just didn't design enough inverter capacity into the system...... What are your thoughts? Max Balchowsky SEE Systems
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