[RE-wrenches] Trace inverters undercharging batteries.

Thu Dec 30 05:24:32 PST 2010

To be honest, I cannot think of any reason ever to replace the electrolyte in a battery except to replace spillage. If the batteries got to the slush or freezing point at less than –10F or so, they probably already had problems with charging.

From: jay peltz 
Sent: Wednesday, December 29, 2010 1:24 PM
To: RE-wrenches 
Subject: Re: [RE-wrenches] Trace inverters undercharging batteries.

Hi Jamie, 

Would slushy electrolyte be an problem for a battery?
Would this call for replacing the electrolyte?

thanks,

jay

peltz power

On Dec 29, 2010, at 8:28 AM, James Surrette wrote:

  Hi Jay, 

  If the froze and it was "slushy" will not cause internal damage. 

  To your point, if they freeze solid - this will generally break the grid and cause internal shorts. 

  I assumed, since the batteries were operational, there is no shorts. 

  Per freezing, here is the chart on freezing points and SG levels; 

  1.280 -92° F (-69° C) 
  1.265 -72.3° F (-57° C) 
  1.250 -62° F (-52° C) 
  1.200 -16° F (-27° C) 
  1.150 +5° F (-15° C) 
  1.100 +19° F (-7.2° C) 

  Regards, 

  Jamie

  >>> jay peltz <jay at asis.com> 12/29/2010 12:16 PM >>>
  I'd like to go back to the freezing battery part as I don't live in real freezing territory. 

  How could they actually freeze and not destroy the housing, internal plate structure and in the end work at all? 

  thanks, 

  jay 

    From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan Sindelar
    Sent: Wednesday, December 29, 2010 10:41 AM
    To: dahlsolar at 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
    Allan at 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 

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