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Old 07-21-2021, 04:24 PM   #1
Mini-Skoolie
 
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Condensation in battery compartment - typical?

Just had our bus delivered today (2006 40' FE Thomas). It drove 220 miles w/o issue en route.

Was very surprised when I opened up the battery compartment after the trip to find i) it was hotter than blazes and ii) had lots of condensation.

I am a verifiable noob when it comes to operating this sort of vehicle, so here come the dumb questions:

i) is this normal?
ii) if not, where should I start to troubleshoot?
iii) any other questions I should be asking?
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Old 07-21-2021, 06:40 PM   #2
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Make sure that isn't battery acid! Was it raining during your drive, or did you go through puddles? Or is there something leaking from above?

What is hot? The battery, or the space?

Is your bus battery indicator showing normal or something else?

Do you have a voltage meter to check the state of charge (when bus is off) and charging voltage (when bus is running)?
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Old 07-21-2021, 07:12 PM   #3
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As Rucker indicates, looks like the batteries have been significantly overcharged, which causes them to get hot and outgas acidic fumes and explosive hydrogen gas.

The sense line in the alternator which tells when the batteries are charged may be faulty
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Old 07-21-2021, 08:41 PM   #4
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Get right on this! Batteries when over charged can blow up and make a big dangerous mess. Just ask any mid fifties VW owner (like me) who had one blow up under the back seat!
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Old 07-21-2021, 09:36 PM   #5
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Thanks all -

No rain or anything leaking from above

The space was very hot, smelled very caustic (can't think of a better word), and (failed to mention in original post) I could see what looked like steam coming from the liquid when I first opened the compartment. I didn't think to take a look at the battery indicator (the bus is being stored about 30 mins away from my home, so I can't take another look until this weekend).

Sounds like an overcharging problem

GIVEN THAT:
  • Would this diagnosis be confirmed by a high voltage indicator on the dash a) immediately after start-up, given the potentially overcharged state in which the batteries were left or b) after running for a period of time (about how long?)
  • Any alternative diagnoses I should consider?
  • Assuming I'm safe/competent with basic electrical and eager/willing to learn, any reason I shouldn't try to fix this myself?
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Old 07-21-2021, 09:54 PM   #6
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Sounds like the alternators regulator has failed so it outputs voltage too high, which will cook the batteries. Might be as simple as replacing it. Should remove it and have it tested.
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Old 07-22-2021, 06:54 AM   #7
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I'd check the batteries first. A bad battery will also cause overcharging. In some cases the over charging comes from the regulator sensing the need for more current causing the overcharging.
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Old 07-22-2021, 08:37 AM   #8
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The first step is to disconnect and remove the batteries. After you do that, neutralize all of the acid and wash out the compartment thoroughly. Then you treat any rust/paint any bare metal, and your battery compartment will be good to go.

After all of that, you can then identify the source of the problem. You're clearly boiling the battery acid, so something is wrong. Step 1 in testing/inspecting a charging system is to actually test the batteries. You'll likely find that your charging system is actually okay, but that you have 1 or more batteries that are junk, and that is what's causing the situation. If the batteries are okay, then you can move onto testing the charging system. I'll post the steps for that if necessary.

But what typically happens is that one of the individual battery cells shorts out internally, making your 12.6 volt battery a 10.5 one. The remaining cells will then be grossly overcharged when hit with 14+ volts from the alternator, and their acid will begin to boil out.
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Old 07-22-2021, 12:39 PM   #9
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Quote:
Originally Posted by BeNimble View Post
Sounds like the alternators regulator has failed so it outputs voltage too high, which will cook the batteries. Might be as simple as replacing it. Should remove it and have it tested.
My shuttle bus has a 15A voltage regulator in line between the starting battery and the secondary battery. It's mounted on the firewall under the hood, right below the windshield wiper.

If the Alternator regulator failed, that would theoretically provide secondary control-if you have one.

So maybe the battery has a fried cell as Booyah mentioned.
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Old 07-22-2021, 12:51 PM   #10
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Quote:
Originally Posted by Rucker View Post
My shuttle bus has a 15A voltage regulator in line between the starting battery and the secondary battery. It's mounted on the firewall under the hood, right below the windshield wiper.

If the Alternator regulator failed, that would theoretically provide secondary control-if you have one.

So maybe the battery has a fried cell as Booyah mentioned.
It sounded like the high-voltage alarm was on, which would indicate not the batteries. But re-reading it, seems the question was maybe "if" it was on.

The batteries are probably toasted and need replaced, if there are two it is simple matter to test them. Certainly anyone diy a motorhome should have a voltage meter and know how to use it.
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Old 07-23-2021, 08:04 AM   #11
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Thanks all - grateful for the guidance

I have a voltage meter and know how to use it

Off to the races

I'll fire back after everything is wrapped up
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