[RE-wrenches] Sealed battery test/maintenance

[robert ellison]

It is a timed test to do it correctly, load the bank to 25 amps or what ever
load the spec is and measure the battery voltage every 15 minutes (take a
starting voltage unloaded first)
until the first battery drops below 1.75 VPC
That is the first battery to fail. Do it till they are all at 1.75 VPC. The
battery that make it closest to 6 hours is the best, the ones that fail
first are the worst ones. Bet you figured that out without me...
You have to adjust the load as it moves around as the battery gets
discharged fully.
When done charge them back up. Hard to do in an off grid situation.
When new the entire pack should take the load and be dead at 6 hours of
draw.

Bob

On Wed, Dec 17, 2008 at 12:22 PM, Peter Parrish <
peter.parrish at calsolareng.com> wrote:

> I am very interested in this thread as we too have about a half-dozen
> grid-tied battery backup system in the field. I used to be a ham radio
> operator and I remember using large, wire-wound resistors encased in an
> aluminum casing. The case could be bolted to a heat sink.
>
> I looked up one of these puppies and found them rated up to 50W continuous.
>
> Here is a simple tester:
>
> Assume a single 12 V battery. If you want to test battery banks, I think
> that that would be a different ballgame altogether.
>
> Use a number of 5 ohm / 50 watt resistors in parallel. The number you use
> depends on the current you want to test to. Assuming that you want to run
> at
> C/20, here is how you determine how many resistors you need.
>
> A 5 ohm resistor will draw 2.4 amps. Assuming C/20, a single resistor would
> be an appropriate load for a 48 Ah battery. The power drawn is 28.8 W which
> is fine for a 50 W resistor as long as it is bolted to a good heat sink.
> Two
> 5 ohm resistors will draw 4.8 amps, appropriate for a 96 Ah battery. The
> general formula is "battery capacity divided by 48 gives you the number of
> 5
> ohm / 50 W resistors you need in parallel". The power dissipated in each
> resistor will always be the same regardless of the number in parallel.
>
> I will probably rig one of these loads up one day soon if a better solution
> isn't out there already.
>
> One could add a high current switch or DC rated circuit breaker, voltage
> probe point and a high precision shunt to measure current.
>
> I have no idea what sort of voltage as a function of time should be. Has
> anyone spoken to battery manufacturers about the specs under C/20?
>
> - Peter
>
> Peter T. Parrish, President
> California Solar Engineering, Inc.
> 820 Cynthia Ave., Los Angeles, CA 90065
> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
> CA Lic. 854779, NABCEP Cert. 031806-26
> peter.parrish at calsolareng.com
>
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Glenn Burt
> Sent: Wednesday, December 17, 2008 7:41 AM
> To: 'William Miller'; 'RE-wrenches'
> Subject: Re: [RE-wrenches] Sealed battery test/maintenance
>
> Thanks for the reply William,
>
> When you load the battery bank, are you using the inverter as the source of
> the load (obviously with its loads), or do you use an independent DC load
> like a carbon pile (auto battery tester)?
>
> Glenn
>
> -----Original Message-----
> From: William Miller [mailto:wrmiller at charter.net]
> Sent: Tuesday, December 16, 2008 2:07 PM
> To: glenn.burt at glbcc.com; RE-wrenches
> Subject: Re: [RE-wrenches] Sealed battery test/maintenance
>
> Glenn:
>
> There are a combination of tests, none as decisive as we might like:  Load
> the battery bank and test per cell voltage (more often we find warm
> connections revealing related problems).  Measure the at rest voltage.
> Measure voltage over time at load.  If you are serious about this,
> establish
> base lines when batteries are new.
>
> Good luck.
>
> William Miller
>
>
> At 09:55 AM 12/16/2008, you wrote:
> >Good Holiday Season to all:
> >
> >Does anyone have a sealed (gel & AGM) battery test/maintenance
> >procedure they would feel comfortable sharing with the group?
> >I have been tasked with creating one for our company now that we have
> >more than a couple of grid tied systems with battery backup.
> >
> >Hate to re-invent the wheel with so much talent available here.
> >Thanks in advance!
> >
> >Regards,
> >
> >Glenn Burt
> >Technical Specialist
> >
> >Renewable Power Systems, LLC
> >PO Box 967
> >Averill Park, NY 12018
> >V: 518-674-5808
> >C: 518-810-3174
> >F: 518-514-1175
> >E: gburt at RPSPower.com
> >www.RPSpower.com <http://www.rpspower.com/>
> >
> >
> >
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