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*
al...@sindelarsolar.com <mailto:al...@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.chamber...@redwoodalliance.org>
> To: RE-wrenches <re-wrenches@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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