digital battery hydrometer [RE-wrenches]

[Joel Davidson]

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Hello Dan,

Thanks for the voice of reason and experience...and the mellow photo of an 
ASI16-2000 on your website.

Anyone care to share their written instructions for batteries and trimetric 
that they give to homeowners?

Best regards,
Joel Davidson

----- Original Message ----- 
From: "Dan Fink" <danbob at otherpower.com>
To: <RE-wrenches at topica.com>
Sent: Friday, February 15, 2008 10:36 AM
Subject: RE: digital battery hydrometer [RE-wrenches]


>
> Hi all -- I've been following this 'why I abuse my batteries' thread for
> quite some time now. Besides RE system install experience, I have
> experience in liquid process control.
>
> Everyone here knows what a nightmare customer battery bank abuse is for
> the system designer, seller and installer. Repeated repair calls,
> damaged batteries, and blame flying between customer and RE wrench.
>
> The short answer-- you CAN buy a digital battery hydrometer, and also
> in-situ acid hydrometer sensors for battery process control. But, the
> issues involve can quickly take you WAY past something that's practical
> for a home-scale RE system.
>
> --A battery acid refractometer is an option if you must do lots of SG
> tests for customers. They range from $80 for automotive grade to $300
> for lab grade. You'll still be using a turkey baster to draw the sample,
> and must clean it all after every sample. And you have to keep in mind
> temperature compensation.
>
> -- a (relatively) inexpensive handheld digital battery hydrometer is
> commonly available and might be a good option for an RE Wrench that has
> to check battery banks frequently. It will at least prevent acid holes
> in your Carrharts, since the pump is usually built in....no turkey
> basters. These units also measure temperature and provide a corrected SG
> reading. Most can be PC interfaced into a spreadsheet. However,
> inexpensive versions generally require that the sensor be cleaned after
> each use, just like inexpensive pH meters, etc. They can't be
> permanently submersed in electrolyte.
>
> -- in-situ sensors are also available. They are expensive. These STILL
> need to be removed from the electrolyte and calibrated at least yearly.
> Generally a network of sensors is used, into a PC data acquisition
> program. Though i suppose you could just use one. But.....
>
> What I don't understand is WHY go to all this expense? Just monitoring
> SG on one battery cell of a large bank is not going to help you or
> customer learn much of anything about how the system is performing,
> except to detect gross problems. And those you can detect with a $200
> Tri_metric. A couple grand spent on digital specific gravity metering of
> a couple cells won't give you any clue at all about problems in any of
> the other myriad cells in the battery bank.
>
> If you want a fool-proof battery monitoring system, you can buy one.
> They use them in nuclear submarines, telecom backup power centers,
> utility grid switching stations, etc. The SG and temperature of the
> electrolyte in each cell is monitored individually. Control of charge
> current can actually be performed on each series and/or parallel string
> of cells and in some cases individual cells. If a part of the battery
> bank gets too far off the SG of the rest, the charging current to just
> the affected parts can be adjusted to compensate, then alarms go off and
> make automated cell phone calls to the supervisor, and technicians go
> searching for bad connections and loose wires with a thermal imaging
> camera!
>
> My advice is:
> --never install a system without a Tri-metric or E-meter to track NET
> amp hours and kilowatt hours...inputs vs loads, tracked over time.
> --research the cost/benefit ratio of a digital handheld hydrometer vs.
> your extra time spent with the turkey baster plus cost of new Carrharts
> per year.
> --Recommend a battery check-up by YOU every year. And check every single
> cell with the hydrometer!
> --Also check carefully for loose wires and bad connections when you do
> your service call. I would place these at #2 in top causes of battery
> failure. A SG monitor would not detect this unless it was installed in
> the cell(s) that was dying from starvation...it would only detect the
> effect of the bad cell spread over the entire bank.
>
> In my opinion, a system monitor that reads Specific Gravity from only
> 1-3 cells is a false friend. The BEST system monitor in the world is an
> experienced RE Wrench armed with historic system data from a Tri-metric,
> a turkey baster and good glass float hydrometer, a multimeter....and
> Carrharts with lots of holes in them from battery acid. If he/she shows
> up in brand new coveralls.....ask for a picture of the last coveralls
> before hiring! (grin)
>
> DAN FINK
> Technical Director
> http://www.otherpower.com/
>
>
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>
>
>
>
> 


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