Good points, Allan, and I agree about the brand choices if you can afford them. Regarding the strings, I always try to go with two series strings for remote locations. In the event of a battery failure, there is always the option to go down to one string in an emergency. Of course, most of my off-grid experience is in the Caribbean where replacement batteries are often 4-5 weeks away.
Jason Szumlanski Fafco Solar From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Allan Sindelar Sent: Wednesday, December 29, 2010 10:41 AM To: dahlso...@gmail.com; RE-wrenches Subject: Re: [RE-wrenches] Trace inverters undercharging batteries. Jesse, Don't waste your time on those batteries; they are all toast. Don't replace them with the same; four strings is poor design. Read the article about off-grid batteries in the current Home Power, and then sell the customer a set of 12 (or 24; either one string or two is OK) 2V industrial cells, such as HUPs from Northwest Energy Storage or K-series Surrettes. Size unknown. The existing full bank was 1400 A/hr if the cell cases had black covers, 1600 A/hr if the tops are blue, to give you an idea. BP modules from 1998 would have most likely been 12V 75W or 85W, meaning 900-1000 watts; too small an array for that size battery bank if the home is used full-time; OK for a seasonal or weekend cabin. Only with new batteries can you even tell what the inverters are doing. My hunch is that the inverters aren't at fault. However, given the poor quality of the original installation, they likely are set to default setpoints, which can charge at a very high rate (about 220A at 28.8V for two if the gennie is big enough) but won't get batteries full (and can't equalize them), as the default setpoints are too low. And I'll bet dollars to doughnuts the default setpoints are in place, as the inverters have been shut down sometime in the last 12 years, losing any original programming settings. You might see about getting an experienced off-gridder in your frozen region to work with you. Maybe Darryl could consult now, then make one trip out to set up the system once the new batteries are in. This was the classic late-90s system with a later charge controller upgrade, but if you have never worked with this equipment, you're likely to set it up for a repeat failure years down the road. Just read Jamie's post - while his advice is spot on, of course, you need to decide if it's worth your while. I'd be more inclined to try his approach if the battery bank was three years old, not 12. That's a huge amount of time spent, working with acid and an unknown set of hazards, with at best the possibility of a few years' use. I'd suggest that unless it's your father-in-law's cabin, and you value the chance to hang out there for a week, it's not worth your time or the customer's, especially given that you acknowledge having little off-grid experience. Allan Allan Sindelar al...@positiveenergysolar.com <mailto:al...@positiveenergysolar.com> NABCEP Certified Photovoltaic Installer EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com <http://www.positiveenergysolar.com/>
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