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kittysmitty
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# Posted: 25 Apr 2024 11:33am
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I'm doing some load testing on some batteries. I have noticed that AGM's seem to hold the voltage and drop slowly, but at around 50% they drop like a rock. FLA's just the opposite. Voltage seems to drop quicker early but once they hit 50% it slows down. Anyone have any comments or observations?
And please don't comment on how much a battery should be discharged as this is just for testing purposes.
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paulz
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# Posted: 25 Apr 2024 01:45pm
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I may have seen what you describe. Are you actually load testing? I have seen low voltage FLAs that will still lake a load, where AGMs that still read decent voltage won’t do much load. No idea why.
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gcrank1
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# Posted: 25 Apr 2024 05:21pm
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Ive had both agm's and la that hold a decent voltage reading but don't have much for usable amp hours.
To me it is the ah's that are important.
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gcrank1
Member
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# Posted: 5 May 2024 10:13pm
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Just saw on diysolarforum that the 120v hair dryers run off an inverter make great load testers.
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paulz
Member
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# Posted: 7 May 2024 12:16am
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Quoting: gcrank1 Just saw on diysolarforum that the 120v hair dryers run off an inverter make great load testers.
Just dug one up. Oldy oldy but works
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gcrank1
Member
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# Posted: 7 May 2024 12:25am
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Waiting on the road test report Paul 
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paulz
Member
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# Posted: 7 May 2024 01:27pm
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Ok. What am I supposed to do, just jump a spare inverter to a battery and turn on the dryer? Is it going to tell me something my load tester doesn’t?
Heaven knows I have plenty of half dead batteries around here, both FLA and AGM.
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gcrank1
Member
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# Posted: 7 May 2024 01:37pm
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Typical automotive load tester (afaik) puts on a heavy load as if using the starter to start an engine. Maybe the fancy ones have an adjustable load?
The hair drier on Hot will draw per the label rating for the low or high speeds letting you watch the bat sag from load over x time; ie, more like what deep cycle bats are rated by.
For lfp you can take a fully charged one and load steady until the lvd and find out what real world usable power you have in it vs the stated ah's.
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paulz
Member
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# Posted: 7 May 2024 01:49pm
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Makes sense. Shoot I left that dryer at the house, be a few days..
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paulz
Member
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# Posted: 7 May 2024 10:20pm
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While waiting.. today a friend brought over his weed blower for me to fix (simple, rotted fuel line). The good part is he gave me some solar stuff he no longer uses: a renogy 100w panel, wanderer controller and 1250w inverter (msw I’m sure).
The controller has no digital read options, but it does have Sealed, Gel and Flooded battery settings. I wonder what the differences are?
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paulz
Member
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# Posted: 8 May 2024 01:47am
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Found the charging differences between battery types.
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paulz
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# Posted: 8 May 2024 02:36pm
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Started wondering about the charging differences (at least with this Renogy controller) and how it might affect load. There is no LFP setting (it’s an old one I guess), and no AGM either (maybe that’s the sealed setting).
Anyway drove me to this good description of the different battery types. Kind of long, haven’t digested it all yet.
https://www.foxtronpowersolutions.com/gel-battery-vs-lead-acid/#:~:text=On%20the%20ot her%20hand%2C%20sealed,with%20a%20glass%20mat%20substance.&text=And%20gel%20batteries %20are%20filled%20with%20silica%20to%20coagulate%20the%20electrolyte.&text=Besides%20 that%2C%20sealed%20batteries%20are%20virtually%20immune%20from%20spills%20and%20leaka ge.
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paulz
Member
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# Posted: 11 May 2024 05:33pm
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Ok first highly unscientific test done. Not much learned really, except I got some dud batteries. All showed full charges, over 12.5 overnight. The two big FLAs ran the heated dryer no problem, time indefinite as they would likely do it for hours. Of the smaller sealed bats, (AGMs?) only the fairly new one (2023 date) that runs my cart would run the dryer. The others would not even get it started.
Same results with the load tester, three tested in the green, the others went to nothing right away. Not much to learn really, except even after testing the bad ones still showed 12+ volts. So I guess you can have useless ones that still show good voltage.
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gcrank1
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# Posted: 11 May 2024 08:15pm
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That is true, and at 12v a '12v battery is pretty much dead/the beans are gone.
But! A bat that is that far gone for any real power can likely still run LED lights and I think USB chargers.
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paulz
Member
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# Posted: 12 May 2024 02:11pm
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Quoting: gcrank1 But! A bat that is that far gone for any real power can likely still run LED lights and I think USB chargers.
True, I’ll test one today. But, maybe for no longer a time than a little LFP 18650 and more trouble to keep around.
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paulz
Member
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# Posted: 30 May 2024 01:40pm - Edited by: paulz
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Bit of fooling around this week..
Couple months ago I bought a FLA car battery from a city house neighbor. It’s a few years old but was never used or charged, it was his backup sump pump battery. Still looks new but dead, I gave him 20 for it, figuring I could always get 10 back, which is what Napa gives me for cores.
Put it on a grid charger for several days and it did finally light the green light, measured over 12.5. But the load tester went to fail immediately and it was back under 10v right away.
Brought it to the cabin after reading the recent thread on equalization/boost charging. Here I have a couple old HF panels, the smaller ones that measure around 18v. So I’ve had that battery hooked direct (no controller) for a couple days* hoping it might jar some sulphate loose. Gets up over 12.5 but still dies as soon as unhooked. Oh well, looks like another Napa core.
*I read that panels do draw some juice at night with no CC.
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ICC
Member
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# Posted: 30 May 2024 06:09pm
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Quoting: paulz *I read that panels do draw some juice at night with no CC.
I don't think that has been true for decades
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paulz
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# Posted: 30 May 2024 07:35pm
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Ok good. I only did a quick search and read the highlighted. I did try putting a VOM on a panel in the dark, nothing.
From https://shopsolarkits.com/blogs/learning-center/do-solar-panels-drain-batteries-at-ni ght#:~:text=It%20explains%20that%20while%20solar,compatible%20with%20the%20battery%20 voltage.
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gcrank1
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# Posted: 2 Jun 2024 06:26pm
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To the original post:
The comment about how the two type bats went to 50% then beyond slipped by me.
They both are lead acid chemistry
They both are best Not regularly depleted to 50%, def not beyond (it kills them); max 25-30% use off the top will give you the longest bat life.
Both need to be recharged asap or they will sulfate, which also kills 'em. Lead Acid bats Like to be kept fully charged.
Also, LA charges rather slowly. The initial goes fairly good, then the amps in drop off (internal resistance) and the final run to the fully charged turns into a slow walk.
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kittysmitty
Member
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# Posted: 5 Jun 2024 12:10pm
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From the original post
"And please don't comment on how much a battery should be discharged as this is just for testing purposes."
And for a "Load" I use multiple 100watt light blubs with an inverter.
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gcrank1
Member
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# Posted: 5 Jun 2024 01:38pm
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Many people read this forum and not all are aware and/or follow the comments and reasoning of things being discussed (or think they do but don't).
Imo restating fundamentals from time to time isn't a bad thing. Sorry it offended you.
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kittysmitty
Member
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# Posted: 5 Jun 2024 10:56pm
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My apologies, sometimes I'm a little cranky before my first coffee
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gcrank1
Member
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# Posted: 6 Jun 2024 12:33pm
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And the frustration from the battery issue
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paulz
Member
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# Posted: 6 Jun 2024 02:43pm - Edited by: paulz
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Speaking of apologies; I mentioned on the 30th the new/old FLA I got. So it’s been at the cabin hooked to 18v solar panel sans controller (1 amp or less). Poured some epsom salt in it, very carefully as you can see. Been stuck at 10.7 volts. Had my bat tools out yesterday for other stuff and stuck the load tester on it. Surprisingly it didn’t go down all the way like the dead ones usually do. Below the “good” range though as expected. Then checked it with the hydrometer, 5 cells in the green, one stone cold dead red. Hmm, maybe got a usable fla with one dead cell..
In the spirit of further time wasting, maybe I’ll drain that cell, flush it out or something and fill with good electrolyte out of another battery. 10.7/5 x 6 = 12.8!
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gcrank1
Member
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# Posted: 6 Jun 2024 03:29pm
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Let it go, Paul, let it go
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paulz
Member
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# Posted: 6 Jun 2024 05:51pm - Edited by: paulz
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Careful gcrank, you’re in danger of suspension from the Cabin Cheapskater’s Club (CCC). 
I dumped that cell and the 2 next it in a pan, tapped on the bottom and refilled them with that mixture. On the charger, showing 12 and change so far but it’s done that before.
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ICC
Member
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# Posted: 6 Jun 2024 06:33pm
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Quoting: paulz In the spirit of further time wasting, maybe I’ll drain that cell, flush it out or something and fill with good electrolyte out of another battery.
I think you nailed it as a waster of time.
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paulz
Member
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# Posted: 6 Jun 2024 10:42pm
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Probably but I have a lot of time these days, everything is done, lol. On the bright side, it starts and runs my cart. Only a V twin Briggs but it turns it over fine. The cart has a solar charger on the roof, I’ll unhook it and see how the battery lasts but it’s always there. 13.2 at the moment.
Glancing around, there’s the 3 tractors. 2 carts. Log splitter, generator, dump truck, 56 Chevy. All 12v car battery powered. Half sits battery les but nice to have spares around. Lugging car batteries isn’t as easy as it used to be!
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gcrank1
Member
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# Posted: 6 Jun 2024 11:11pm
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Iffn its working leave the solar hooked up, LA likes to be kept charged! (and you do want it to work when you want rather than putz with it, right?)
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FishHog
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# Posted: 7 Jun 2024 01:42am
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I like to putter and experiment and waste time. Perk of being retired, but you are fighting a losing battle Paul.
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