[RE-wrenches] Voltage discrepancy
boB Gudgel
boB at midnitesolar.com
Sat Aug 14 15:10:26 PDT 2010
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
>>>> 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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>
> 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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