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How do I tell if my chassis batteries are toast

Yahoo Message Number: 91711
Resending, got an error saying mails to me from list have been bouncing, think I reset.
I suspect my chassis batteries in my 2003 Lexa (2 lead-acid 8D's in parallel) have given up the ghost. They show full charge (12.7 volts from the echo charger, coach has been on 50amps for a couple of months), but if I try to start the coach, the dash and everything else shuts down after about half a second, as if the batteries are dead. They'll then show 10.x volts but float up to 12 pretty quickly, but I suspect they can't give any current to start.
If I hold the battery boost button down for a while (like a couple of minutes) I can get the engine to turn over.
It's possible that it's both the echo charger, AND the inverter reading false voltages...
They are charged (since I'm sitting) solely from the echo charger. My inverter can equalize the house batteries, but not the chassis batteries (unless I do some major re-wiring). I have a couple of 40amp digital automotive chargers with equalization mode, but I suspect they won't be able to try equalizing the 8D's (they shut off after a few hours even on charge, if batteries have dropped low, as they must assume something is wrong if a battery can take 40amps for multiple hours).
These are the chassis batteries that were in the coach when I bought it 2.5 years ago, I had the house batteries replaced at that time, but chassis batteries (though totally flat when I first looked at the coach, it had been on the dealer lot for > 1 year) haven't given me any problems until now.
Not convenient for me to get to a repair service, I don't have anything (other than engine/starter) to throw a big resistive load on the battery.
I've got three quarters of a mind to just order a couple of new 8D's. Lifeline's etc. (AGM) seem to be ~twice the price of lead-acid, makes sense for house, but thoughts on AGM vs. lead-acid for chassis? http://www.1000bulbs.com/product/56352/BAT-UB8DAGML4.html at $436 seems like a good price for an AGM 8D (+$90 shipping each to me, still

-Jim Walsh
2003 Lexa

Re: How do I tell if my chassis batteries are toast

Reply #1 –
Yahoo Message Number: 91714
Jim

Interstate 8D sealed maintenance free batteries are a good compromise in between the price of a standard lead acid and AGM. No adding water and no gassing.

Dan 2006 Allure 31348 C-9

Re: How do I tell if my chassis batteries are toast

Reply #2 –
Yahoo Message Number: 91716
Jim, I agree with Dan. I can't recall, sorry, who it was on this board that pointed me towards the CAT 8D Maintenance Free batteries. He was right, as they had the highest CCA ratings I could find. And, long time board Member, Tom with a Pevost now, and a Lifeline Distrubutor - thought that these were a good choice for my coach. (And yes, I did get his help and did buy X4 L16's AGM for the coach duty. Painless experience, good help from Tom on choosing the right battery. And, with our ISL we only have one engine 8D battery.)
The CAT 8D's will cost you a bit more, but hopefully they are a quality battery.

Best of luck on you battery hunt,
Smitty

04 Allure 31017
04 Allure Sold to a nice new owner! Now enjoying a 07 Magna Rembrandt 45' ISX600 #6775
"We're ONDROAD for THEJRNY!" (Toad and Coach license plates, say Hi if you see us!)

Re: How do I tell if my chassis batteries are toast

Reply #3 –
Yahoo Message Number: 91724
Your batteries are probably toast from what yous say. Couple of things you can do.

Make sure you coach charging voltage is over 13.5 volts
Check the specific gravity after you've charged the batteries.
Connect an external charger to the batteries and watch the charging current (after the batteries are "dead"). If you have a bad cell(s) the charging current will be low or become low very quickly.
Once the batteries are charged, try to start and look at the voltage drop on the batteries and the recovery.
I have a carbon pile that I bought at Harbor Freight, makes checking batteries a little easier.
Judy n Joe 98 Intrigue 10578

Re: How do I tell if my chassis batteries are toast

Reply #4 –
Yahoo Message Number: 91727
YOur batteries may well be toast. However since the voltmeter reads 12 volts shortly after trying to start the engine, I would suspect the battery terminal connections are slightly loose with possibly some corrosion between the posts and the terminals. Loosen the clamp terminals at the posts, remove the terminals and clean the posts and the inside of the terminals. Then reseat the terminals on the posts and tighten securely. Many times a loose terminal will allow the battery voltage to be measured since there is virtually no current flow from the battery. However, as soon as a heavy current tries to pass from the post to the terminal, the loose or corroded connection will act like a very large resistor - dropping all of the voltage across the joint. This is why everything goes dark as soon as you try to start the engine. Oddly enough, removing the heavy current load will allow the high resistance connection to carry enough current to allow the voltmeters to register the true battery voltage. If you have someone to help and you also have a separate voltmeter, measure the battery voltage with the leads directly on the posts (not on the terminals). Keeping the leads on the posts, have your helper try to start the engine - if the battery voltage drops down and then comes back up after releasing the key it is probably bad batteries. If the voltage stays up then it is a bad connection at the terminals (you can also try the same test with the voltmeter leads on the terminals rather than the posts - if it is bad connections, the voltage will drop down very low while trying to crank the engine but then return to 12 volts after you release the key - it may take a minute or so for the post to terminal resistance to drop enough to let the voltmeter read the battery voltage). Do not use the battery boost capability while doing these tests.
I just reread your post and see that you have 2 batteries in parallel. When you have the terminals off the batteries, measure the voltage on each battery independently. One battery could be dead or very weak under load - however since the voltage is 12.7 volts with no load, I am going to go with bad connections. You can try the tests above with each battery (one battery disconnected and then repeat with the other battery disconnected). If one battery does OK and the other doesn't, then the one battery that doesn't may be shorting internally under load.

John

'06 Inspire DaVinci #51905

Re: How do I tell if my chassis batteries are toast

Reply #5 –
Yahoo Message Number: 91754
Jim,

The UB8D looks like a good price but it is made in China. !?? The Lifeline AGM is quite a bit more but also a little more Amp Hour rating and slightly heavier. (good indication)
http://www.powerstridebattery.com/lifeline-gpl-8da-deep-cycle-agm-battery

My chasis batteries were doing the same thing and Infinity Coach recommended replacing with Deka Sealed batteries (not AGM) for considerably less. I will stick with AGM's for the house batteries though.
John

08 Intrigue #12235
10 Ford Escape

Re: How do I tell if my chassis batteries are toast

Reply #6 –
Yahoo Message Number: 91831
Thanks John, this makes sense. Did this test, w/ voltmeter shoved into the lead posts of the batteries. 13.1 showing at start. Dropped to 12.8 when I turned on the key. Left battery (to which both are cabled through) showed drop to 4.5 volts after turning ignition key on, seeing dash drop, wait a couple seconds.
Releasing key, voltage back up to 12.1. Right battery, same thing, drop to 3.8 volts. So batteries are shot, which is what I suspected. But great advice for how to verify battery versus bad connection somewhere that can't carry the starting current. Voltage shown at batteries within .1 volts of what my Silverleaf dash was showing (at least when it had enough voltage to stay turned on J)
Will see if I can find a couple of sealed lead acid 8D batteries in Seattle/Redmond area tomorrow morning, otherwise we'll take the pickup on the weekend trip.

Thanks all for the great advice,
Jim