[RE-wrenches] Trace inverters undercharging batteries.

Wed Dec 29 12:37:06 PST 2010

Hi Jay, 

To previous posts, I would question why the battery is able to freeze.

Assuming nothing drastic, if there are fine ice crystals in the battery
which cause no pressure on the plates, the battery will generally
recover without incident.  Once the battery warms, the slush melts and
SG's will rise as the battery recharges. 

However, if there is "ice" in the battery and any deforming of the case
- the battery is very likely destroyed.  Moreover, be very cautious when
recharging such a battery as it will undoubtedly have a short. 

Regards, 

Jamie 

>>> jay peltz <jay at asis.com> 12/29/2010 4:24 PM >>>
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 -92Â° F (-69Â° C) 

1.265 -72.3Â° F (-57Â° C) 

1.250 -62Â° F (-52Â° C) 

1.200 -16Â° F (-27Â° C) 

1.150 +5Â° F (-15Â° C) 

1.100 +19Â° F (-7.2Â° 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 ( mailto: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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