[RE-wrenches] Voltage discrepancy
Drake Chamberlin
drake.chamberlin at redwoodalliance.org
Sun Aug 15 07:53:24 PDT 2010
At 06:33 PM 8/14/2010, you wrote:
> how often they run theri generator.
>Darryl
They are almost never charged on the generator. Last winter the
batteries got fairly low in cold weather and had to be charged on the
generator via the inverter.
The cabin has intermittent usage. When the cabin was left empty for
6 weeks, the owner came back and put 3 1/2 gallons of distilled water
in the 4- L 16s.
The bulk and float voltages had been left at factory default by the
original installer, which is low enough for sealed batteries. This
setting is low for vented, liquid lead acid. So the voltage settings
shouldn't cause the water loss. The automatic equalization was
disabled, due to the fact that the system has DC loads that could be
damaged by voltages over 30 V.
The original voltage reading discrepancy on the MX 60 was early in
the day, when the array was partly in the shade. Later that day,
when the batteries were receiving full charge with power tools and
other loads on the system, the MX 60 gave correct readings.
Thanks,
Drake
>--- On Sat, 8/14/10, boB Gudgel <boB at midnitesolar.com> wrote:
>
> > From: boB Gudgel <boB at midnitesolar.com>
> > Subject: Re: [RE-wrenches] Voltage discrepancy
> > To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> > Date: Saturday, August 14, 2010, 5:10 PM
> > Drake Chamberlin wrote:
> > > boB,
> > >
> > > Thanks, I will check all connections when I get
> > out there. Is there anyway a loose connection could
> > cook the batteries?
> >
> > A loose connection, if it was like I described, would tend
> > to under-charge the batteries. I would
> > think that
> > if there were ~that~ much of a voltage drop, and
> > significant current, you'd have a pretty hot connection
> > somewhere. Although, if the connection is bad enough,
> > you might just get the CC to get to Absorb or
> > Float voltage and that would at least limit the current but
> > maybe not enough..
> > Of course, loose connections may not be the problem, but
> > that's what I look for first.
> > I would measure the voltage at the CC terminal block and
> > see if it is telling the truth.
> >
> > If the CC is telling the truth, then she may have a bad
> > connection, and then
> > it's Warning Will Robinson !!
> >
> > Could be intermittent too. Then ya may
> > want to start wiggling and banging on things.
> > It sure worked well with TV sets.
> >
> > boB
> >
> >
> > >
> > > Thanks,
> > >
> > >
> > > Drake
> > >
> > >
> > > At 03:16 PM 8/14/2010, you wrote:
> > >> Drake Chamberlin wrote:
> > >>> I called her back just now, and the voltage
> > readings on the Mate, MX and Trimetric all match.
> > Humm.
> > >>> The batteries are 4, 4 1/2 year old, U.S.
> > Battery L-16s wired in 24 volt configuration. It seems
> > that I remember postings of Wrenches having problems with
> > these batteries. There is about 1 KW STC of PV on the
> > roof.
> > >>
> > >> Might want to be careful of loose
> > connections. Maybe the MX was putting out some
> > high(ish) current and there
> > >> was a voltage drop across that connection, and now
> > they are reading the same because the current is
> > >> lower from the MX. i.e. high voltage
> > at the terminals of the CC and lower at the actual battery
> > terminals.
> > >>
> > >> boB
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>>
> > >>> At 12:12 PM 8/14/2010, you wrote:
> > >>>> Any way she can get a real
> > voltmeter? the MX60 has voltage calibration, so does
> > the FX it sounds like something is over charging,
> > perhaps the generator run? additonal
> > details on battery bank size, array size and typical
> > load. Darryl
> > >>>>
> > >>>> --- On *Sat, 8/14/10, Drake Chamberlin
> > /<drake.chamberlin at redwoodalliance.org>/*
> > wrote:
> > >>>>
> > >>>>
> > >>>> From: Drake
> > Chamberlin <drake.chamberlin at redwoodalliance.org>
> > >>>> Subject:
> > [RE-wrenches] Voltage discrepancy
> > >>>> To: "RE-wrenches"
> > <re-wrenches at lists.re-wrenches.org>
> > >>>> Date: Saturday,
> > August 14, 2010, 8:58 AM
> > >>>>
> > >>>> Hello Wrenches,
> > >>>>
> > >>>> I just got off the
> > phone with an off grid system owner who has a
> > >>>> voltage
> > discrepancy showing between the reading on her MX-60 and
> > >>>> both her Mate and
> > Trimetric meter. The MX-60 shows 28.8 V and
> > >>>> the Trimetric and
> > the Mate both show around 25 volts. The
> > >>>> batteries are
> > using a tremendous amount of water.
> > >>>>
> > >>>> Has anyone seen
> > this scenario before? Do you think the MX-60 is
> > >>>> bad?
> > >>>>
> > >>>> Thanks,
> > >>>>
> > >>>> Drake Chamberlin
> > >>>> Athens Electric
> > >>>> OH License 44810
> > >>>> CO License 3773
> > >>>> NABCEP TM
> > Certified PV Installer
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> > 740-448-7328
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> > 740-856-9648
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> > > Drake Chamberlin
> > > Athens Electric
> > > OH License 44810
> > > CO License 3773
> > > NABCEP TM Certified PV Installer
> > > Office - 740-448-7328
> > > Mobile - 740-856-9648
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Drake Chamberlin
Athens Electric
OH License 44810
CO License 3773
NABCEP TM Certified PV Installer
Office - 740-448-7328
Mobile - 740-856-9648
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