Once the electrolyte has been changed out, all bets are off for using SG as an indicator for state of charge. Jamie Surette gave excellent commentary on a similar thread recently on how to handle a situation such as this.
Mick's suggested procedure (below) will work, with caveats. Be sure you use a meter that records accumulated watt-hour usage in non-volatile memory. You'll be connecting the meter on the AC-side of the inverter, and when the AC goes off due to low DC input voltage, the meter will go off as well. The basic Kill-A-Watt meter (and perhaps others?) forget everything when the power goes off. P3 (mfgr of the K-A-W meter) make a model P4460 that "remembers" values even when powered down. Others likely do as well. I would recommend using incandescent lamps as a safer and more easily adjustable load. Parallel three 100 watt lamps on a power strip. With a meter (above) measure the actual power drawn by the lamps. As a backup "timer" for testing batteries, I use an ordinary analog clock .. the type with moving hands (remember those?). Got mine from a big-box store. It uses 3 watts, so is an insignificant load compared to 300-400 watts. Set the clock to 12 am and start your test. The clock will stop with the total run time when the inverter shuts off. Speaking of inverters .. use a model that requires a manual reset after low-voltage shutdown. Some types will automatically start back up if the voltage rises high enough again. This could give you a bit of a false reading as to total capacity Be careful. Dan --- On Wed, 1/26/11, Mick Abraham <m...@abrahamsolar.com> wrote: From: Mick Abraham <m...@abrahamsolar.com> Subject: Re: [RE-wrenches] Load testing batteries? To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org> Date: Wednesday, January 26, 2011, 9:19 AM Hello, Jesse~ Instead of trying for laboratory precision, here's a way to measure the battery capacity using equipment that you may already own: * Gather up appropriate safety stuff: gloves, goggles, baking soda, distilled water, off duty fireman, blast protection, etc. * Connect only two of the 6 volt batteries in series to make a 12 volt battery string. Put those on charge once you're sure they're warmed up & thawed out. Maintain about 75 degrees Fahrenheit air temperature in the testing area. Recharge quality is important if you want to give the batteries a fair opportunity to show what they can do. * Install a DC breaker between battery positive and the positive DC terminal on a 12 volt inverter. The inverter should be 500 watts or bigger with AC plug in receptacles; you can connect inverter negative to battery negative & power it up on the DC side. * Plug into the inverter with an AC kilowatt-hour meter (such as Kill-a-Watt, the Brand meter, WattsUp?, etc.) then plug into the kWh meter with an adjustable blow dryer. * Switch on the hair dryer at a low setting then dial up on the heat until your AC meter shows about 360 watts of power draw. The battery pair, if new, should be able to sustain a drain like this for about ten hours--this is based on the 298 amp-hour rate for that battery on the Rolls spec sheet. * Run the blow dryer until the inverter shuts off due to low voltage, then read the number of AC watt-hours that were clocked by the kWh meter. 298 amp hours X 12 volt nominal = 3,576 watt-hours. Battery professionals would replace a battery if it fails to deliver 50% of the original rated power. * Repeat this same test with the other battery pairs. As mentioned, this approach is not scientifically perfect, but it might be done with minimal outlays for new equipment...and the results will be close enough. Jolliness~ Mick Abraham, Proprietor www.abrahamsolar.com Voice: 970-731-4675 On Tue, Jan 25, 2011 at 10:53 PM, Jesse Dahl <dahlso...@gmail.com> wrote: Wrenches, I have some (4) rolls 6 volt batteries 4000 series S-460. They are from a stand alone system in Ely, MN I have mentioned in a previous question. I had mentioned in the previous post that they were suspected to have been frozen (bulged cases). The owner took them out of the system, dumped the electrolyte out and added new electrolyte. I have no idea what she added or any specifics. I did a SG test today, all of the cells seemed to have 50% SOC, but I don't think that means anything. Most of the info I got from the last post and from my knowledge tells me the batteries are shot. They are 10 years old at least. What I'm asking, I guess, is what type of load tester would a person need to load test a battery like this. I have a cheap one, up 160Ah I believe, but I'm not sure if it will work this test. I have limited battery experience and would appreciate any help with testing methods. Thanks everyone, Jesse Sent from my iPad!!! _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org 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 -----Inline Attachment Follows----- _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org 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
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