Generator AGM Start Battery Suddenly Dead

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JackConnick

Veteran Member
Joined
Aug 19, 2022
Messages
45
Vessel Name
Paradox
Vessel Make
1991 Grand Banks 36 Classic
Hi;

We've been having very high heat here in the PNW lately. Engine room in my 36 GB was 110F yesterday. I have Victron volt/temp sensors on my batteries. last night the Group 27 Lifeline start battery suddenly lost all voltage, like from 11v to .5v over a couple of hours. Battery temp showed 105F. I double checked with a voltmeter.
I suspect the environmental temperature was just too high for it. My house AGM bank (3x 200 amp) seems unaffected.
I'm out on a cruise and need to get another battery, going into Anacordes this am to do so. I am looking at a West Marine 1000 CCA SLA battery. I have a Northern Lights 5.5 genset. Is that enough?
I think for start batteries a lead acid will work better...?
 
AGMs actually make better start batteries than house banks.

Are you sure it’s just the high temps which drained it? Weird that the other bank was not affected. Check for something that may have drained the battery. A previous owner may have wired something into it, like a bilge blower.
 
105 is not too high for a lead acid battery (think of the under hood temps of a car) That said, a failing battery can be pushed over the edge by high or low temps. If the battery is easy to get at for water checks, there’s no particular reason to go AGM. For a generator that size, a group 24 start battery is quite sufficient.

Ken
 
New wiring, new battery last year, nothing else on that line. There wasn't even a dedicated gen start battery when I bought the boat, electrical was a mess. Had it professionally redone.
The battery is a little hard to get to which is why I went with the AGM. I'm thinking the SLA battery will accomplish the same task.

Jack
 
... last night the Group 27 Lifeline start battery suddenly lost all voltage, like from 11v to .5v over a couple of hours.

11V is pretty much already dead. 105F isn't all that high.

Is there a charger for it? Does it work? (I ask because we recently discovered our genset battery charger wasn't.) And/or does the generator's alternator charge the battery? Does it work? (Ours does, but the previous flooded battery -- installed by the PO -- apparently had a pretty steep self-discharge rate.)


The battery is a little hard to get to which is why I went with the AGM. I'm thinking the SLA battery will accomplish the same task.

Hard to reach has always been a good enough reason for me. Lifeline does make 2 different kinds of 12V AGMs, some they rate as for starting, some as for deep cycle. I'd expect extra $$$ if any for the deep cycle version wouldn't be cost effective for a starting-only battery.

-Chris
 
My ER temps are way higher than 105F for typical summer cruising with no ill effects on FLA batteries.
A "low maintenance" FLA (think sealed caps) with high CCA would be ideal -I just use NAPA, good price and rugged (GRP 31 used to start heavy equipment all over the country)
You need a DC clamp meter to ensure that you generator alternator is in fact charging the battery. Your 11v as a starting point suggests it was not being charged.
 
Thanks all.

Took battery in and yes it was dead. I tried charging it, I have a dedicated new 3 bank Victron 50/3 amp charger just for the isolated start batteries. It was not taking a charge.

Also ran over to Anacordes for 1.5 hrs and I have 2x newish 90 amp chargers that were pooring amps out to it. It was a 195 deg when we pulled in. Yes, I have a clamp meter and have just had them into the shop and tested myself as well. Voltage came up, but no CCA.

I have no idea why it died, it was an expensive battery. I had suspected it was maybe bad earlier, probably due to too small a battery charger on the start batteries - which had died. I think it did damage to this battery. I took it into Fisheries and they tested it and said it was fine.

Anyway I put in a West marine group 24 1000CCA SLA that started it just fine. It actually has similar CCA as the old Lifeline group 27.

I think the electrician was smoking something when he said we could mix AGM and flooded start batteries, then sold me too small a charger that wasn't a 3 bank, only a 3 circuit.

Cheers, thanks.

Jack
M/V Paradox
 
If the battery was 195 degrees then it failed for sure, probably with a shorted cell. When that happens, it acts like a lower voltage battery and “normal” charging is way too high and causes the battery to overheat.

Ken
 
Battery cells short for all kinds of reasons. I even got a new battery from a very reputable manufacturer with a defective cell. It just happens. Sadly, there are few technicians who know how to Test a battery and none of them work at Fisheries Supply. If they just through a resistance tester on it and pronounced it good then I know for sure they are clueless.

It only takes one defective cell to cause the remaining 5 cells to work overtime to make up for the bad cell. At first things will work but the battery will have a very short life span.
 
Maybe you were unlucky and got a defective battery. The charge profiles for AGM and SLA overlap in some respects, I`m mixing them without any apparent issues pending replacing my main 200AH 8D SLAs which serve house and start, and charge bowthruster and genset AGMs. There are AGMs sold here with a 1000 CCA rating as well as 200AH (or greater) storage capacity rating.
What charges your genset battery? If it`s only the genset alternator only when it runs it`s probably not getting enough charge. On a previous boat I had a modest solar panel charging mine via a simple regulator.
 
I have gone to all AGMs... 8D diesel start & B& S thruster
+ a pair of 8Ds paralleled for house. AGMs usually conevwith CCA as well as AH ratings as, unlike FLA, they provide both services well.
I removed my Gen batty from the 3 bank charger as I didn't think it best to have a GP27 charging along with all 8Ds. The gen has its own alt that charges when running. I also added a jumper to a 1-2-all Sw on my house that allows emergency gen start from house ans well as periodically topping off the gen batty if not used often.
I've never had to use the house to start gen but nice having the insurance.
 
I removed my Gen batty from the 3 bank charger as I didn't think it best to have a GP27 charging along with all 8Ds.
Never gave this any thought. 3 bank or 3 circuit? Are these chargers for 3 banks isolated from each other and what turns off charging. I would hope that when a bank is full, that circuit shuts off.
But if all shut off when all reach charge I can see how G27 would get overcharged.
Anyone know for sure?
 
Steve... I dont know how mine actually handles multi banks @ different SOC but assumed charge continues to all 3 banks but the Amperage tapers off as each bank increases V & SOC.
I now have (1) 8D on each bank so all similar in size but will be different SOC between start & house frequently.
 
Good choice on the new battery design. You likely have 3x the battery that you need, but that is just fine.

My 8 kW Onan & my seldom (3 +/- times a year) used 20 kW Onan are both started with their own Group 24 1000 MCA VRLA (some say sealed) Johnson Controls manufactured battery which I got at Walmart about 8 years ago. At the time they we the cheapest battery I could find. BTW, so are my 1100 cubic inch main engines, although there are 4 Group 24s per engine.
Neither is charged by anything but the on engine alternator, but neither do anything but start the gensets and run the primitive electronics. These genset start batteries, just like your car's start battery should not need anything but the alternator if you run it for 30 Min. every 3 months or so.
Your genset's alternator likely has voltage set points for a wet lead acid battery, not an AGM, which could be part of your problem.
All that being said, my battery's temperature has never exceeded 85º F. and is most often about 50º F.

I have never opened the cells of my batteries to add water.
They still perform for all intents and purposes, as new.
 
AGM start batteries have their place. If size is an issue AGM will excell. If you need to store in a non vertical position again AGM. For start, cranes and thrusters I find SLA to be the better value but there are other circumstances that can make SLA not an acceptable choice.
 
AGM batteries certainly do have important use cases. Starting a NL 5.5 kW genset (about a 0.8 liter engine) is likely not one of them.
 
I think the electrician was smoking something when he said we could mix AGM and flooded start batteries...

It's not out of the question. Can depend on actual recommended voltages for specific batteries. Sometimes FLA battery maker A and AGM battery maker B happen to recommend the same voltages (or very close, close enough) for bulk, absorption, and float.


a charger that wasn't a 3 bank, only a 3 circuit.

????

-Chris
 
Battery cells short for all kinds of reasons. I even got a new battery from a very reputable manufacturer with a defective cell. It just happens. Sadly, there are few technicians who know how to Test a battery and none of them work at Fisheries Supply. If they just through a resistance tester on it and pronounced it good then I know for sure they are clueless.

It only takes one defective cell to cause the remaining 5 cells to work overtime to make up for the bad cell. At first things will work but the battery will have a very short life span.
They actually bought a better tester and gave it a pretty good going over, as they determine warranty, I had no choice to go with what they said. And it worked fine for a while longer.
But I think it had an intermittent short and the heat and stress finally did it in.
Bitch of it is that I couldn't take it back for an exchange as I'm out cruising now...
 
I think the electrician was smoking something when he said we could mix AGM and flooded start batteries...

It's not out of the question. Can depend on actual recommended voltages for specific batteries. Sometimes FLA battery maker A and AGM battery maker B happen to recommend the same voltages (or very close, close enough) for bulk, absorption, and float.
Yeah, that was the thought, Lifeline said is was only 1/2v difference with a flooded battery. But after this experience, I'm not buying it.

a charger that wasn't a 3 bank, only a 3 circuit.

????

The first charger the electrician recommended was supposed to just be a trickle charger for the start bank of the 2x 8D FL + 1 Grp 27 AGM.
However what this charger does is to divide the available amps. ie 25/3, so you end up with too small a charger per bank. It over worked itself and shorted, then over charged the batteries.

I took it out and went a much better 50amp - true 3 bank - charger, ie 3x 50 amps. Yes, its overkill but a few bucks for a better charger seemed like a good idea.

Jack
 
Yeah, that was the thought, Lifeline said is was only 1/2v difference with a flooded battery. But after this experience, I'm not buying it.

1/2V could be a big deal, in some cases. For example, Lifeline wants 13.3VDC +/- .1V @ 77F for float (per their manual), and I suspect 13.8V instead could maybe lead to premature failure.

In a world where "12V" doesn't really mean exactly "12.0V"...

-Chris
 
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