boiling batteries.

[1956_4x4]

1. What are the voltage readings at the batteries prior to starting the vehicle?

2. What are the voltage readings at the batteries right after starting the vehicle while the engine is running?

3. How many amps are each of the alternators putting out and does this output taper off after the vehicle runs for a while?

4. Do the voltage readings at the batteries drop slightly after the vehicle has run for a while?

Your system might be operating normally, depending on when the readings are taken and the static charge condition of the batteries. I would say that the main problem I've seen with these systems have been the connections at the batteries. A tight connection is important, but it's worthless if the connection isn't clean.

Smitty

 

[rmgill]

Ok, define boiling?

Are you getting tiny bubbles? Or are you talking a rolling boil with steam coming from the battery vents?

 

[Keith_J]

What model of truck?

You mention you have dual alternators with dual batteries.

 

[tankie88]

Right.Truck is a M1009.Not both batts are bubbling.Just the rear one.When running i can hear it bubbling.can i test the amps out of the alternators with a multi meter??

 

[stampy]

Ok here is your issue....I had THE EXACT SAME THING GOING ON IN MINE! 1) Remove battery conections and clean 2) apply dielectric grease (can buy at autozone) Make sure you clean and grease the connection from battery 1 to battery 2 where the 24v circut is made. Mine happened all of the sudden after cleaning and finding where my dirty connection was the problem was solved!

 

[stampy]

Mine LOOKED OK...Just a little junk between the bolt head and the wire made all the difference. Use a wire brush or sandpaper to make sure all of your connections are shiny.

 

[Cucvnut]

Thats good advise for anyone who gets a CUCV and needs to install new batterys.

 

[Keith_J]

Right.Truck is a M1009.Not both batts are bubbling.Just the rear one.When running i can hear it bubbling.can i test the amps out of the alternators with a multi meter??

One way to measure alternator output is with a clamp-on inductive meter, these aren't cheap but is the easiest.

The other way is with an ammeter. A big one, 100 amperes. Bear in mind you must install the meter (or the shunt) in the charging series.

Best bet is measure charging voltage, noting over 14.5.

 

[tennmogger]

My money is on a bad battery with high internal resistance. The 14.5-14.8 voltages you are measuring is ok, and well balanced, but is sufficient to cause the bubbling in a battery that's weak. Bet when you start the truck the voltage drops substantially across that battery that bubbles. If you didn't have a 24v system the truck probably would not have started.

IMHO you need to replace both batteries. Checking specific gravity with a hydrometer would prove the failure, but many batteries these days are sealed and can't be checked. Are your batteries the 'maintenance free' type?

Bob (who admittedly knows nothing about an M1009)

Right.Truck is a M1009.Not both batts are bubbling.Just the rear one.When running i can hear it bubbling.can i test the amps out of the alternators with a multi meter??

 

[Keith_J]

Check grounds/interconnects. If there is a problem with grounds, the alternate current loop will cause the regulators to act funny.

Remove the connections, clean with wire brush and then reassemble, coating with anti-oxidant grease to protect the raw metal surfaces.

 

[stampy]

I thought I had a bad battery also as my posts were clean and so were the clamps. I tested the voltages and got similar readings. The high resistance was BETWEEN the 24v connection and it caused 1 battery to "boil" Luckily I figured it out about 30 minutes after I first noticed the battery charging indicator climbing toward the red and finally staying in the red. I actually thought I had lost the voltage regulator and was overcharging so I tured on everything (which did drop the voltage onto the line between red and green. Now It stays mid green and I have not changed the batteries and have taken a 10hr trip in the truck hauling a trailer...so I hope this helps someone.

 

[rmgill]

A badly discharged battery WILL bubble when it's charging. Charging current is the most then. Put a battery on a charger and look at it as it's charging. check the charging voltage. If it's within spec then keep the electrolyte up and don't worry about it.

 

[cagosti]

you have a bad battery one or more cells bad
your 12 volt battery becomes a 10 volt battery
and is over charged by 14 volts. SO IT BOILS

 

[tankie88]

Right chaps,(before starting) front batt..12.38v rear 12.32v
(running) front batt..14.20v rear 14.62v
(off, after a short drive) front batt..front 13.60v rear 13.70v

will clean all the terminals later and see what diff that makes.If that don't work i take it the rear batt must be knackered?

 

[tennmogger]

You really need some load on a battery when measuring the voltage to evaluate it's condition.

And, the batteries should not be in parallel, either (does the M-1009 parallel the batteries when not in starting mode?)

The only test that means much would be with a battery load tester, one battery at a time, but even a headlight bulb across a battery for a while would allow measurement of a loaded voltage.

As someone said, a GOOD battery will not gas until it is satisfied with the charge level, at any alternator current allowed by the regulator. A bad battery can gas with hardly any charge.

After that test drive, did either battery feel hot? As internal resistance goes up, the battery will heat more.

Bob

Right chaps,(before starting) front batt..12.38v rear 12.32v
(running) front batt..14.20v rear 14.62v
(off, after a short drive) front batt..front 13.60v rear 13.70v

will clean all the terminals later and see what diff that makes.If that don't work i take it the rear batt must be knackered?

 

[tankie88]

Right chaps....long time.New batts fitted,altenators have new regulators.The old rear batt must of been u/s.No battery bubbling now.But volt meter still in red.Front batt has 12.6v and rear has 12.5 when off.When started front has 14.4v and rear has 14.5v.Altogether 29.1 when running.Volt meter still in red.Ideas????

 

[1956_4x4]

Chack the voltage at the volt meter while running. If the voltage is good, replace the meter. If the voltage is low, locate the bad connection. Glad to hear that you're making progress!

Smitty

 

[stampy]

+1 check voltage at the volt meter. Chances are it's bad. does it drop when running lights or your fan?

 

[tankie88]

It only drops when i start up and the glow plug relay is clicking on and off.

 

[stampy]

When the plugs are on mine is just above the red mark in the yellow. Then it is in the yellow close to the green when the relay kicks off. Mine typically sits about center between yellow and green when running (unless it has taken me longer to start it and the batteries are recovering then it is mid green)