[RE-wrenches] Batt Cap AGM

Wed Nov 21 14:06:51 EST 2018

I agree with Allan,  I have never done a full load test on a battery 
bank.  The customers experience usually provides the necessary info.  In 
this case there is no question the battery bank needs replacing.   Here 
are the reasons to replace in summary:

1)  Battery wiring in parallel/ then series, with too many parallel strings

2) Age of the batteries, 5 years is not bad for an average AGM in even 
good conditions.

3) Odd brand not suited for solar, with outrageous life expectancy claims.

4) 100 AH, 12 v batteries are just not the right choice for anything 
over a single series string.  Larger 6 v batteries are always preferred 
when possible and have longer cycle life because of thicker plates.

5) Wide variance in voltages between batteries (13 to 15 v?)

6) Customer's experience: obviously the service call came in, because 
the system wasn't performing properly anymore.

Load testing this mess is just a further waste of everyone's time.  
Temporarily rewiring the best batteries into a normal series/ parallel 
configuration with maybe 3 strings at most could regain a bit of 
performance until the the new set can be installed.

Ray Walters
Remote Solar
303 505-8760

On 11/21/18 11:40 AM, Sindelar Solar wrote:
>
> Mick,
>
> While I fully agree on the importance of a monitor such as the 
> TriMetric, I'm confused by some of what you've written below. A TriMet 
> (or any similar monitor for LA) can measure amp-hours removed and 
> replaced, but it can't measure & display the battery bank's amp-hour 
> capacity. Only taking the time to drain the bank at a measured rate 
> will do that, and I have yet to have a customer want to pay me to do a 
> battery capacity test down to 1.75 vpc at the 20-hour rate - or any 
> rate for that matter. The TriMet is set up such that the installer 
> tells the TriMet the battery capacity. In a case such as this, what 
> number would you program into the TM as the amp-hour capacity? How 
> would you determine this value?
>
> Thanks, Allan
>
> -- 
>
> *Allan Sindelar*
> allan at sindelarsolar.com <mailto:allan at sindelarsolar.com>
> NABCEP Certified PV Installation Professional
> New Mexico EE98J Journeyman Electrician
> Founder (Retired), Positive Energy, Inc.
> *505 780-2738 cell*
>
> On 11/20/2018 11:28 PM, Mick Abraham wrote:
> > Hello, Drake & All~
> >
> > Drake described his service dilemma about batteries bought elsewhere 
> & whether to correct the original hinky pack wiring (copied below). My 
> reply below may seem cynical & I may seem too eager to declare the 
> existing battery as: "Failed". Call me jaded.
> >
> > Mick's $0.02 is: If there's no amp-hour monitor in the system, I 
> suggest you first try to persuade the homeowner to buy a metering 
> shunt & a modest amp-hour meter such as the Tri-Metric--which could be 
> used to measure & display the battery bank's amp-hour capacity. If the 
> client won't approve that expenditure (& hourly labor for 
> explanations), the service tech is hamstrung. Nobody can measure the 
> health of a battery bank by just looking at it or talking about 
> it...and clients sometimes receive the inevitable "battery bad news" 
> if they are shown the diminished capacity on a digital display after 
> an equitably managed "pump & dump".
> >
> > Your thought, Drake, of holding back on any re-wiring of the battery 
> pack...seems prudent...until the first set of amp-hour measurements 
> are recorded as a baseline. From there...a common pattern is a series 
> of attempted remediation efforts--all for pay, of course--until the 
> homeowner acknowledges that it's time to start afresh.
> >
> > Oops, I left out an important step: getting a read on whether the 
> client has the money for new batteries or not. I'm personally terrible 
> at getting that reconnaissance done early enough. If the client isn't 
> materially blessed to be able to get new batteries, they might be 
> better off spending limited funds on fuel for the engine generator 
> instead of on battery testing & tutorials.
> >
> > Mick Abraham, Proprietor
> > www.abrahamsolar.com
> >
> >     ---------- Forwarded message ----------
> >     From: Drake <drake.chamberlin at redwoodalliance.org>
> >     To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> >     Cc:
> >     Bcc:
> >     Date: Tue, 20 Nov 2018 11:41:17 -0500
> >     Subject: [RE-wrenches] Batt Cap AGM
> >     Hello Wrenches,
> >
> >     An owner of an existing system has a bank of twenty, 100 AH, 12 
> V Deep cycle batteries of the Batcap brand.
> >
> >     The bank is made up of four sets of 5 batteries in parallel to 
> produce 500 AH battery sets at 12 V. These four parallel sets are then 
> wired  in series to give a 48 V nominal bank.
> >
> >     The battery voltages vary from around 13 to 15 volts. The bank 
> is about 5 years old. The CEO of Batcap told the system owner that 
> these batteries have lasted up to 30 years in solar applications, so 
> he has high expectations for these batteries being around for a while.
> >
> >     My first impulse is to rewire the bank in a normal series - 
> parallel configuration. But there are too many strings to do this 
> without a bus bar. Besides, the batteries are likely damaged, and 
> rewiring them might cause the bank to exhibit unsuspected problems. 
> How much money is worth putting into this bank? $0?
> >
> >     The owner seems like a reliable guy who likely hired the wrong 
> installer. He could use some help. What would you do in this 
> situation? Rewire the bank, leave it well enough alone or run for the 
> hills.
> >
> >     Thanks,
> >
> >     Drake
>
>
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