AGM Battery alternator charging/ possible alternator issue

[Newbiecampers]

Hi all,

Searched for some time now for an answer to this but am not coming up with exactly what I was looking for. Plus most battery/battery charging threads end up being 14 pages long with details that start to make my eyes water.

When starting to use our Class C this spring I noticed our starting battery (stock flooded) had leaked a little acid. Had never done this before. Did not think much of it at first. Also noticed our "2nd isolated" chassis battery (on frame rail under coach) may have leaked a little as well. House batteries as well showed a little leaking and corrosion on posts. More than I had seen in the past.

Took our first short trip. After about 2 hours of driving on the way back home started to smell what I characterized as "battery charging" smell (venting). House batteries are under steps and inside of house.

Next morning, went out to check house batteries and saw much more leaking/corrosion. After moving RV a day or two later saw acid stain on driveway as well. Removed house batteries and had a lot of clean up/repainting to do in compartment.

Mulling over the situation, thought about the only common connection between all 4 batteries is the alternator. It is a 220 amp alternator that is part of the "RV package" on the chevy 4500 chassis. I checked the alternator voltage output at the starting battery and it was 15.3 volts right after start. I let it run for 1 hour and 20 minutes, checking around every 10 minutes, and it never went below 15.07-15.1, and that included around a 10 mile drive. Prior to starting the engine the starting battery voltage was 12.9 and the 2nd battery was 13.05. Looking back at some old notes, I saw that previous voltage had also been 15+ after start. House batteries were not hooked up/were out of the camper.

The questions:
-Want to replace my toasted house batteries with AGM. With the batteries being within the envelope of the house I don't want any further chance of fumes coming in. Especially with the kids. Should I be concerned with the alternator constantly charging at 15 volts? I have yet to see it go under that. We often drive for 8+ hours in a day. Do I need to put something/some device between the alternator and house batteries to stop/control the charging? I am also going to replace the wfco converter with a progressive dynamics, but we do alot of "boondocking" and don't do alot of converter charging anyway.

-Does it sound normal that the alternator output never seems to go below 15.07 volts, especially considering the batteries were almost full charge anyway? I am wondering if this alternator has a problem with voltage regulation and has been cooking the batteries, leading to the failure of the house batteries after roughly 1 year 7 months. I'm going to talk to a Chevy dealer about it/have them check it out before I put the new house batteries in as the alternator would still be under warranty.

-Any recommendations on some group 24 size AGM Deep cycle batts that don't break the bank?

[Newbiecampers]

Sam Spade wrote:

Ductape wrote:
The alternator is overcharging. If its warranted still, I'd ask for replacement of the batteries as well, as consequential damage directly resulting from the faulty alternator.

+1

If you don't get that charging voltage down, it will fry your new batteries too. AGMs too, only a bit slower.

You aren't gonna like the price of a "true" deep cycle AGM.
I got mine from an independent battery shop......at about $200 each.
NAPA wanted $300 each.

Call around to auto parts stores, boat dealers and battery specialty shops in your area. Even an RV dealer or two maybe.....but that would be my last choice.

Sorry Sam, didn't see this post last night.

Yep. I definitely want to get this alternator voltage worked out before I put in any new house batteries. The compartment is empty right now with leads taped off.

$150-200 is what I have been finding as well. Sam's had a group 27 deep cycle for roughly $160, and a grp 31 for $180 or so. No group 24 of course :S..... But bobndot presented an interesting solution for the lack of room.

[Newbiecampers]

Sam Spade wrote:

Newbiecampers wrote:

Off to the dealership to start to work on this alternator (potential) issue.

Good luck.

But it is not a "potential" alternator issue.

The max. charging voltage should be about 14.5 and it should not even stay at that for very long.

The regulator is built into the alternator these days so unless there is a wire pinched and shorted out somewhere.....it just about has to be the alternator.

Note: Having said all that......mine runs at about 14.3 ALL the time. That concerns me a little but so far no problems.

Ha ha...thanks for the well wishes.

It went about as I figured it would: nowhere really. The specs they looked up (same place they would for trouble shooting) said the target charging output in "charge mode" is 13.9-15.5, and that depends on state of charge and estimated batt temp. They didn't seem to think they could get any test to indicate replacement is needed. What I could not seem to get accross is that it does not seem that it should be staying at 15+ volts all the time. I have not come accross any battery type so far that would want 15+ volts in perpetuity. I very well could be wrong about it all, however...lol.

Goint to call a different dealership tomorrow that I know does alot of work on larger fleet-type chassis such as this Express 4500.



Bobndot: thanks for the idea and links for the extra battery mount. Had not thought of that. Could allow for some bigger batteries.

[Newbiecampers]

theoldwizard1 wrote:
I concur with Ductape ! Much too high ! Something is the chassis wiring could be "tricking" the alternator, but it need to fixed soon. You have already "hurt" your batteries. Don't expect them to live a long life.

Researching this overcharging issue online I came accross some sentiments similar to your's regarding something in the wiring possibly being an issue. One thing I saw mentioned a couple of different places was checking all of the ground connections. I'm going to do that tomorrow. Make sure all I can find are tight.

The house batteries are definitely "hurt." Especially the one of them which leaked much more than the other. I'm going to replace both. Not going to limp them along.

Cleaned up the batteries with baking soda/water last summer.

After looking back at some old notes on voltages, it would not suprise me to find out that this alternator has been perpetually putting out 15+ volts the whole time we've had it.

I'm also going to put my stand-alone charger (ctek unit) on both the starting and second chassis battery to ensure they are both fully charged to potentially rule that out as a reason the alternator may be "stuck" in 15+ volt mode.

[bobndot]

Newbiecampers wrote:
Would like to have done 2 of the group 27 duracell marine agm but it won't fit. Too long

agm's basically do not off-gas.
You could install one inside a cabinet and one in the batt box. I have one grp31 inside dedicated to my 40" tv which draws a lot of watts on 12v. (65w) and inverter for the SAT recvr. (22w)
The other two grp27's are in my OEM batt tray which run the coach. The one inside gets charged independently when I run my genny. The other 2 charge off the converter. That keeps them separated for independent charge rates because the batts are two different sizes.

Another option could possibly be an undercarriage battery box that secures to the frame. Like on the order of a TorkLift box or any welder can fabricate what you need.

https://www.dualpumps.co.uk/products/9918-4821__Undercarriage_Battery_Box

https://www.etrailer.com/Battery-Boxes/TorkLift/TLA7728.html?feed=npn&msclkid=3a7411912e2919c6bcf04d...

[Sam_Spade]

Newbiecampers wrote:

Off to the dealership to start to work on this alternator (potential) issue.

Good luck.

But it is not a "potential" alternator issue.

The max. charging voltage should be about 14.5 and it should not even stay at that for very long.

The regulator is built into the alternator these days so unless there is a wire pinched and shorted out somewhere.....it just about has to be the alternator.

Note: Having said all that......mine runs at about 14.3 ALL the time. That concerns me a little but so far no problems.

[theoldwizard1]

Newbiecampers wrote:
I checked the alternator voltage output at the starting battery and it was 15.3 volts right after start. I let it run for 1 hour and 20 minutes, checking around every 10 minutes, and it never went below 15.07-15.1, and that included around a 10 mile drive.

Ductape wrote:
The alternator is overcharging. If its warranted still, I'd ask for replacement of the batteries as well, as consequential damage directly resulting from the faulty alternator.

I concur with Ductape ! Much too high ! Something is the chassis wiring could be "tricking" the alternator, but it need to fixed soon. You have already "hurt" your batteries. Don't expect them to live a long life.

When you see acid stains/fluffy corrosion on battery post or cable end that mean that the battery is "outgassing" (acid vapor, usually under pressure, is escaping from inside the battery). AGM batteries are not truly "sealed". They have a way of venting these gases if the pressure inside get too high.

At least once a year, all 12V lead acid batteries, including AGM, should be cleaned with a solution of baking soda and water applied with a "chip" paint brush. Continue to apply the solution until the bubbling stops, then rinse with fresh water.

[Newbiecampers]

MDKMDK wrote:

Newbiecampers wrote:

-Any recommendations on some group 24 size AGM Deep cycle batts that don't break the bank?

https://www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/bci-group-24m/sli24m...

Sam's Club sells Duracell batteries as well, but I didn't see a GR24 size in a quick look at their website.
Duracell is made by East Penn.

The line of Duracell marine deep cycle AGM batts that Sam's has is exactly what I was going to get, but as you stated, they unfortunately do not carry the group 24 size, and they can't order it. Their prices were much cheaper than batteriesplus. Would like to have done 2 of the group 27 duracell marine agm but it won't fit. Too long. I have also found that acdelco has a group 24 marine deep cycle AGM. That may fit in with the remedy for the defective alternator.

I originally wanted to go with 2 6v GC2 golf cart batteries before this problem arose (almost bought 2 at coscto on impulse), but every GC2 I have ever come accross is 11 inches tall, and I can only have 10" tall in the battery compartment.


bobndot: thanks. I'll check those out.


Off to the dealership to start to work on this alternator (potential) issue.

[Newbiecampers]

Ductape wrote:
The alternator is overcharging. If its warranted still, I'd ask for replacement of the batteries as well, as consequential damage directly resulting from the faulty alternator.

Thanks.

I do plan on trying to work something out regarding the batts if the alternator is defective.

[Sam_Spade]

Ductape wrote:
The alternator is overcharging. If its warranted still, I'd ask for replacement of the batteries as well, as consequential damage directly resulting from the faulty alternator.

+1

If you don't get that charging voltage down, it will fry your new batteries too. AGMs too, only a bit slower.

You aren't gonna like the price of a "true" deep cycle AGM.
I got mine from an independent battery shop......at about $200 each.
NAPA wanted $300 each.

Call around to auto parts stores, boat dealers and battery specialty shops in your area. Even an RV dealer or two maybe.....but that would be my last choice.

[MDKMDK]

Newbiecampers wrote:

-Any recommendations on some group 24 size AGM Deep cycle batts that don't break the bank?

https://www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/bci-group-24m/sli24m...

Sam's Club sells Duracell batteries as well, but I didn't see a GR24 size in a quick look at their website.
Duracell is made by East Penn.

[bobndot]

Any recommendations on some group 24 size AGM Deep cycle batts that don't break the bank?

I'm now using Universal AGM's They are working very well so far.

[Ductape]

The alternator is overcharging. If its warranted still, I'd ask for replacement of the batteries as well, as consequential damage directly resulting from the faulty alternator.