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 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] 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:[email protected]] Sent: Tuesday, December 16, 2008 2:07 PM To: [email protected]; 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: [email protected] >www.RPSpower.com > > > >_______________________________________________ >List sponsored by Home Power magazine > >List Address: [email protected] > >Options & settings: >http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > >List-Archive: >http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > >List rules & etiquette: >www.re-wrenches.org/etiquette.htm > >Check out participant bios: >www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
