Resting voltage for an AGM battery at 100% charge is 12.7-13.0V, so it's in the ballpark. However, voltage under load is the important thing. That 12.7V can drop like a rock as soon as you draw some current from it. Hopefully you're good-to-go!
I think this battery is toast
- Thread starter MountaineerTom
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MountaineerTom
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I thought about throwing it in and seeing how it did on a start-up. If it didn't do well, I'd want to try out the new charger, so I figured I'd wait til I get off work tomorrow night at 8:00 pm.
If it drops voltage bad on a start-up, do you think I should try charging on the AGM setting for a while or go straight for the Desulfation/Recondition setting on the charger?
I’d go straight to recondition setting because it’s fully charged now, so that’s not your issue. If it had a bad cell, you wouldn’t get 12.7V. Recharging on the AGM setting would be a waste of time.
MountaineerTom
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MountaineerTom
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MountaineerTom
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MountaineerTom
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I woke up earlier than usual for work this morning so I checked the voltage, installed the battery and started it up.
Voltage when I went out there was 12.96 volts at 7:00 am. When I cranked it up, it dropped to 8.64 or so volts but started. I drove it to work and took my jump pack in case it doesn’t want to start tonight. I guess I’ll put it on the new charger and use the reconditioning setting.
Voltage when I went out there was 12.96 volts at 7:00 am. When I cranked it up, it dropped to 8.64 or so volts but started. I drove it to work and took my jump pack in case it doesn’t want to start tonight. I guess I’ll put it on the new charger and use the reconditioning setting.
MountaineerTom
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Based on that, I’d say she's on the way out. Using a weak battery like that is hard on the starter, just keep that in mind. I'm interest to see what happens after you run it through a "reconditioning" cycle or two. Keep us posted, I want to see if it comes back to life.
Agreed!
Also agreed. The starter is pretty much a constant power load device. It's a little more complicated, but that's the gist. If the voltage drops, the current increases to make up for the voltage loss (volts x amps = watts, which is an unit of power, like hp). Normally, the battery will drop to maybe 11V during starting. Dropping to 8.6V is about a 20% loss in voltage, so current drawn by the starter will increase by about 20% to make up for it. Increased current, as you know, means increased heat. The weak point, current wise, for most starters is the contacts in the solenoid. They can actually weld together slightly, keeping the starter gear riding the ring gear after startup. I've experienced this a couple times over the years. So, if you hear an odd noise right after startup, shut the TJ off! Really bad things will happen if you don't.
I am, too. I have several chargers with the Recondition feature, but I've yet to use it. I'm curious if it can adequately desulfate a battery that was loaded to very low voltages. In the past, I've always ended up replacing batteries drawn that low, but if the Recondition function can revive them, all the better!
MountaineerTom
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Will do. I’m interested too. I didn’t even know about this reconditioning and desulfating until a couple days ago.
MountaineerTom
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Put the battery in Desulfation mode shortly after getting home from work. (Around 9:00 pm) The charger manual says it could take up to 24 hours. I’ll check it in the morning before I leave for work.
When I left work tonight, I checked voltage before starting and while cranking. Results were pretty much like what I posted this morning. Fired up on the first crank though.
When I left work tonight, I checked voltage before starting and while cranking. Results were pretty much like what I posted this morning. Fired up on the first crank though.
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MountaineerTom
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CreepinDeth
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Auto-Desulfator ?? Niiiiiice
You don't see many of the common brands out there sold anymore offering this.
I've got 2 that do, but it was hard to find them years ago. I may buy one of these also
They've actually been quite readily available for the last several years.
My current Schumacher charger doesn't have a desulfate or maintenance mode, which having a few batteries sitting around, I think I could use. If this works for Tom I might go ahead and pickup one of the CTEK chargers that covers it all.
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