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Rover
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# Posted: 28 Sep 2022 22:14
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Hi
I don't think I've posted before but wondering about a tool I should purchase. I need to load test my 12 v batteries as I may have been improperly charging them.
I don't have much luck/trust in automotive garages so I'm thinking of buying a typical load tester analyzer. They all seem for vehicles and focused on CCA. Is that type fine or do I need something different for deep cycle type battery? Any features/brands to look for? My batteries are AGM, 12v, 110 Ah.
Thanks
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Brettny
Member
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# Posted: 29 Sep 2022 07:45
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There are some electronic ones with no carbon pile load. Not sure if they state AH.
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gcrank1
Member
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# Posted: 29 Sep 2022 10:17 - Edited by: gcrank1
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An electric 120vac heating device, a hotplate (use a water pan on it), a small space heater, etc. with a stated Watts draw run off your inverter does it.
1) Inverter must exceed the device load but there is no 'start-up' load like a fridge
2) add in some draw from the inverter, though the biggest part of the draw on the bat will be the device
3) best not to exceed the mfr spec on 'charge rate/discharge rate' for the type of bat
4) then you chart the time it takes for the fully charged bat to discharge to a given point, say 25% charge. Keep in mind that under load the bat under load will initially read lower than it really is. If you are targeting (example only)12.6v let it go to 12.5 on your volt/ohm meter, shut off the load, let the bat settle for 1 hr and re-read voltage.
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Rover
Member
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# Posted: 29 Sep 2022 22:27
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Thanks. I might take a chance buying the tool because I'm lazy.
Thanks for the info gcrank1, I might end up doing that too. I guess I would compare the results between each battery and know which are best but not know how they compare to new.
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toyota_mdt_tech
Member
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# Posted: 2 Oct 2022 12:12
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I have a solid state one, works great, It interrogates the battery electronically, I also have another one with a fixed 125A load, you just hook it up, hit switch for load, watch analong volt meter. It reminds me of a cheese grader.
Cheese grader styleURL
Harbor tools has the cheese grader style too.
Solid State style.URL
I have both, the solid state one is my main go to unit.
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gcrank1
Member
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# Posted: 2 Oct 2022 15:24
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I think load testing lead acid deep cycle bats has some dif considerations than starting bats.
The 'C' rate (charging And discharge profile) I often see is .1-.15C,,that correlates to 10 to 15amps on a 100Ah bat. Loading a dc bat with a heavy starting type load may not be good for it?
That said, Ive done it but I kept the load short and only repeated a couple times. 2 of my big ups agm's failed quickly from a several days of charging and voltmeter read full charge after a long rest. They only ran the cabin stuff a few hours! The load tester indicated BAD so I pulled them out of the bank and actually got better performance from the remaining two than I did with all four. The bad ones were 'pulling the bank down' and being the weak link.
The 'given load' over time within the C-rate should be definitive, but sometimes I want a quick & dirty test for my suspicions. On my old agm's I knew they were dying so it didnt much matter if I stressed them out. I think I ended up getting another moderate use year out of the last two; well one did fail during that year, only the other one made it to the 10ish year finish line.
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Rover
Member
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# Posted: 6 Oct 2022 17:31
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Thanks everyone,
I bought a simple load tester and will take my chance testing the deep cycle type batteries. Hopefully a test won't damage them. I'm heading north to the cabin this Thanksgiving weekend (Canada) and will see what the tester says. I might bring the batteries home and charge each individually with a smart charger and then do a gentle test as gcrank suggested earlier.
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gcrank1
Member
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# Posted: 6 Oct 2022 18:37
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Good plan Rover.
At the cabin, if the bats are reading fully charged and have had no load so that is a 'resting voltage' you can test them, but singly, of course.
Be careful, wear protective clothing, gloves and pref a faceshield. I watched one vid where a guy blew a bat on a workbench test, No protection whatsoever.
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