Santiago
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Testing a AGM?
What's the equivalent of a hydrometer test in a flooded battery? I have a chance to pick up some 12v "gently used" deep cycle AGMs and want to test
them.
I have a multi-meter but that will only test voltage, right?
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larryC
Super Nomad
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You can test them with a voltmeter. I suspect that the batteries are at rest, meaning they are sitting disconnected and not being charged or
discharged. Fully charged agm will sit at about 12.7v. The same as most all lead acid batteries. If you had a load tester that would tell you more
about their potential life. Generally I just test the voltage. If a battery is low it doesn't mean that it is not good it just means it may have been
put out of service before it was fully charged. If that happened a long time ago then it may have started to sulphate so I generally stay away from
the ones with lower voltage. Since you are buying a pig in a poke, don't pay too much for them. Also check the date of manufacture and stay with the
newer ones.
Good luck.
Off grid, 12-190 watt evergreen solar panels on solar trackers, 2-3648 stacked Outback inverters, 610ah LiFePo4 48v battery bank, FM 60 and MX60
Outback charge controllers, X-240 Outback transformer for 240v from inverters, 6500 watt Kubota diesel generator.
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larryC
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Frank
Thanks for the link, some good info there. Seems to be geared to more automotive use batteries but informative.
Off grid, 12-190 watt evergreen solar panels on solar trackers, 2-3648 stacked Outback inverters, 610ah LiFePo4 48v battery bank, FM 60 and MX60
Outback charge controllers, X-240 Outback transformer for 240v from inverters, 6500 watt Kubota diesel generator.
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Bob and Susan
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i'd just pass on the used ones...why bring down a headache
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larryC
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I also have had very good luck with used batteries. I like the 2v batteries and then I put them in series to make what ever voltage bank I need. They
are getting really hard to find though. The best I ever got were some some Absolyte llp they were 5 years old when I got them and they lasted another
6 years.
Off grid, 12-190 watt evergreen solar panels on solar trackers, 2-3648 stacked Outback inverters, 610ah LiFePo4 48v battery bank, FM 60 and MX60
Outback charge controllers, X-240 Outback transformer for 240v from inverters, 6500 watt Kubota diesel generator.
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landyacht318
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A load test is more relevant, when it is known how the battery will perform on the same tester, when new.
Generally AGMS will outperform the same size flooded battery in a common load test. They might test good, and actually be marginal, due to their
lower internal resistance..
As for checking voltage, it means little.
12.7v is Low for an AGM. If my 90AH Northstar AGM is at 12.7v, it has 25AH removed from it and is under a 5 amp load.
The Lifeline GPL-31XT I broke in, had a fully charged resting voltage of 13.16V and is a damn impressive battery.
Voltage has very little to do with state of charge except on a rested battery and only when the batteries fully charged voltage is known.
And AGMs take significantly longer to come to their resting voltage after a charging source is removed. That Lifeline took 7 days to rest at 13.16v.
Day one it was 13.23v.
AGMs also require that they be fully charged more often than flooded batteries. Some of them also require they be recharged at high amperages every
so many deep cycles, and the more often the better.
Lifeline says 20 amps per 100AH capacity
ODyssey says no less than 40 amps per 100AH capacity
Deka and some others will say not to exceed 30 amps per 100AH capacity.
People tend to paint all AGMS with broad brushes. Their actual charge parameters vary widely brand to brand.
People also act like their greater price instills them with magical powers. False, Very very false. They require proper charging, without it they
will not last as long as a flooded battery given the same treatment, and cost twice as much to have less overall lifespan, when their specific demands
are not met.
I would not buy any used battery, unless I knew how they were treated, and this basically means how they were charged, and how low they were
discharged. If the seller Appears supremely ignorant of a battery's requirements, walk away.
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LancairDriver
Super Nomad
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I wouldn't buy used battery's without load testing them. I have seen too many that check out with a voltmeter but won't handle any load. This is a
link to a reasonably priced load meter from Walmart that I have seen an auto shop using.
http://www.walmart.com/ip/39586978?wmlspartner=wlpa&adid...
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Cappy
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Great morning read with a cup of coffee. I now am aware of AGM charging more than I ever thought I could be. They sure work good in all my toys
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