I think this battery is toast

[MountaineerTom]

I think I ruined my battery by leaving some off-road lights on and draining it. From what I’ve read, with it dropping below 10 volts when trying to start, indicates a bad cell. I haven’t had it load tested yet but thinking initially that this battery is bad. When I discovered it dead, I put it on a trickle charger for a bout a day and a half. Checking it Tuesday morning it was still low so I put it on a bigger charger on the to amp setting. It was on that for about a day. This afternoon, this is what happen when trying to start.

It’s an odyssey AGM battery. Thinking of a replacement, I wouldn’t mind having some extra terminals, but I don’t think I like the 34/78 group because of the side terminals being so tight near the fuse box. I think I’ve seen some other batteries with extra terminals on top. Does anyone know what those batteries are?

 

[Jerry Bransford]

I would not attempt to recharge it with a trickle charger, use a benchtop charger and place it on the charger overnight. They are not expensive, I'd go pick one up, like an 8-12 amp model with an AGM mode, before assuming the battery is dead... especially an expensive Odyssey. Then measure its voltage after being on the charger overnight. A fully charged AGM battery will show 12.8 volts when sitting on the bench or without the engine running. There's a good chance you can save that Odyssey battery with a good overnight charge.

 

[deadbeat son]

I use a Group 34M AGM battery. It’s the standard OEM size with a second set of marine terminals on the top.

 

[Jamesval035]

I did something similar a couple of months ago, left the ignition on over a 24hr period. Killed my yellow top. I had a buddy with a Schumacher battery charger. Left it at his house to charge for about 36 hrs. Topped it right off and now have no issues with it. But ya, doing some research and reading, Jerry is right, a trickle charger won’t do much but keep it at its current state.

 

[alittleoff]

As far as battery clamps go, I don't like the side terminals either. And I went with the heavy duty Mil Spec clamps.
The kind with the separate through bolt that you can use simple ring connecters.
I did this when I upgraded my battery cables to match the winch cable size.

 

[BlueC]

@MountaineerTom How old is your battery?

 

[MountaineerTom]

I would not attempt to recharge it with a trickle charger, use a benchtop charger and place it on the charger overnight. They are not expensive, I'd go pick one up, like an 8-12 amp model with an AGM mode, before assuming the battery is dead... especially an expensive Odyssey. Then measure its voltage after being on the charger overnight. A fully charged AGM battery will show 12.8 volts when sitting on the bench or without the engine running. There's a good chance you can save that Odyssey battery with a good overnight charge.

Thanks. I have it out of the Jeep now on my old Diehard charger on the 10 amp setting. I’ll check it out tomorrow. I’ve had this thing since the early/mid 90’s.

I use a Group 34M AGM battery. It’s the standard OEM size with a second set of marine terminals on the top.

View attachment 444626

This may sound dumb, but I have no knowledge of them. Having marine terminals is The only thing that makes if different from a regular 2 post battery? I guess I’m asking is there any difference in a marine battery and a regular car battery?

I did something similar a couple of months ago, left the ignition on over a 24hr period. Killed my yellow top. I had a buddy with a Schumacher battery charger. Left it at his house to charge for about 36 hrs. Topped it right off and now have no issues with it. But ya, doing some research and reading, Jerry is right, a trickle charger won’t do much but keep it at its current state.

Thanks, giving it a better charge now, hopefully.

As far as battery clamps go, I don't like the side terminals either. And I went with the heavy duty Mil Spec clamps.
The kind with the separate through bolt that you can use simple ring connecters.
I did this when I upgraded my battery cables to match the winch cable size.

I don’t so much mind the side terminals themselves, it just seems like they are closer to the fuse box than I’d like. Might be a non issue in reality. I currently have the heavy duty style clamps that came with my cable set from custombatterycables.com a few years ago. I really like them.

@MountaineerTom How old is your battery?

I installed it 6 years and 4 months ago. March 2017.

 

[Jerry Bransford]

I'd switch the charger to its 10A and deep cycle/maintenance free modes.

 

[RMETeeJay]

Thanks. I have it out of the Jeep now on my old Diehard charger on the 10 amp setting. I’ll check it out tomorrow. I’ve had this thing since the early/mid 90’s.

I agree with Jerry that it's a good idea to use a charger that's designed for AGM.

 

[MountaineerTom]

I'd switch the charger to its 10A and deep cycle/maintenance free modes.

Thats what it's on while charging. I just snapped that pic before setting it up.

 

[MountaineerTom]

I agree with Jerry that it's a good idea to use a charger that's designed for AGM.

What does a charger designed for AGM do, or not do?

I'm unaware.

 

[sab]

What does a charger designed for AGM do, or not do?

I'm unaware.

AGM batteries are charged at a slightly higher maximum voltage. Old school lead-acid batteries charge at up to 14.4V or so. AGM charge at up to 14.7V or so. Most "smart chargers" have different voltage and current limits in the charge protocol, too.

 

[deadbeat son]

This may sound dumb, but I have no knowledge of them. Having marine terminals is The only thing that makes if different from a regular 2 post battery? I guess I’m asking is there any difference in a marine battery and a regular car battery?

Doesn't sound dumb to me. Car batteries are rated by CCA, whereas the marine batteries have more ratings: CCA (0*F), MCA (32*F), and capacity. As for the physical construction, I can't answer if there's a significant difference. Oh, typically the marine AGM batteries I found had a shorter warranty period due to the stresses of marine use. I just bought it for the terminals.

 

[MountaineerTom]

I ordered myself a little more up to date charger this afternoon.

https://www.amazon.com/gp/product/B0B7WLTG9K/?tag=wranglerorg-20

 

[Frank M]

There’s some room with the side terminals

 

[BlueC]

I installed it 6 years and 4 months ago. March 2017.

Age wise, there should be life left in the battery, but you may have a bad cell now. I have "woken up" problem batteries in the past by charging them on high amp cycles for 10-15 minutes at a time, but I’ve never done an AGM battery. I think this high amp charging desulfates them. Some new chargers have a built-in setting for that now. It may be worth a try, but you might want to save it for your last attempt.

 

[MountaineerTom]

There’s some room with the side terminals

View attachment 444711

Good to see a visual reference. Thank you!

 

[MountaineerTom]

Age wise, there should be life left in the battery, but you may have a bad cell now. I have "woken up" problem batteries in the past by charging them on high amp cycles for 10-15 minutes at a time, but I’ve never done an AGM battery. I think this high amp charging desulfates them. Some new chargers have a built-in setting for that now. It may be worth a try, but you might want to save it for your last attempt.

Thanks for the info. The new charger I bought has that. I had never heard of that until today.

 

[deadbeat son]

This may sound dumb, but I have no knowledge of them. Having marine terminals is The only thing that makes if different from a regular 2 post battery? I guess I’m asking is there any difference in a marine battery and a regular car battery?

I did remember one other thing about the 34 vs 34M. I believe the marine battery gives up a little in CCA for additional capacity or reserve. In other words, there's a little less short duration oomph in exchange for handling longer duration steady loads.

Hope you're able to revive yours though!

 

[MountaineerTom]

Yesterday I put the battery on the Maintenance Free / Deep Cycle 10 amp charge around 2:00 pm. At that time, it was reading 9.5 volts with my meter. Left it on there until 12:00 pm today (22 hours). At that time it was at 13.27 volts. I wanted to see how much it dropped just sitting there, so it's just been sitting in the workshop floor since then.

These are the readings since noon today when it was 13.27 volts:
13.03 volts at 1:15 pm
12.99 volts at 5:15 pm
12.98 volts at 7:00 pm

I'm going to leave it there until I get off work tomorrow night and see what it does. My new charger is supposed to be here tomorrow, so if it has dropped much or won't start the Jeep, I may charge it on the AGM setting.