Coach Batteries Boiling

[Tom Lopez]

I took the batteries to Interstate and they checked them and said all is good. They checked volts, cell acid, and load check. I put batteries back in coach and ran engine for 1 hour and also drove coach. Alternator was producing 13.9 - 14.9 for average of about 14.4. The batteries read as follows: left battery 7.08 right battery 6.93 and combined @ 14.03 with engine idling at 613 RPM. Alternator output was 14.1 to 14.4. These batteries are getting hot to the touch. Chassis battery running about same volts and battery cool to the touch.

Stopped engine and plugged MH to shore power. I have a Progressive PD9260 converter. After about 40 minutes batteries read: left 6.92 right 6.75 combined 13.67. Chassis battery 13.83. Coach batteries are warm/hot. Chassis battery is cool.

Restarted the engine and the alternator output shows same as before average of about 14.4 but now the coach batteries (left one more than right) is starting to boil and can hear gas escape from fill cover.

I don't get it. Can the batteries be bad even though they test good ??? Can that little difference between the two house batteries be causing the problems ??

Chassis battery is getting same charge volts as the house batteries but yet it is cool and normal while house batteries are getting hot, boiling and gassing.

I'm getting these numbers by using a multi meter on the battery terminals and my scan gauge II for the alternator output volts.

Any and all ideas welcome, I'm lost.

[twinboat]

Here is my thought,

The alternators, internal voltage regulator is bad or if it has a voltage sense wire on it, it is not sensing battery volts.
Corrosion on the sense wire connection lowers the voltage it sees. That causes the alt to overcharge.

Try cleaning any small wires plugged into the alternator.

My cruising volts are 13.6 to 13.8. Watched it today.

[chboone]

Originally Posted by 530ktm

I have never heard of dabbing a few drops on a plate to see how good a cell in a battery is but testing the cells with a hydrometer where you suck up the water in each battery cell is a true test to see how good they are. (Called a gravity test) Also, you may want to put a load test on the batteries as well to see if that shows anything wrong with them.

What Rider Fan is talking about is a refractometer for checking battery acid and coolant. The one in the link is expensive, I have seen them for less. A few years back I bought one at Harbor Freight for $30.00, they don't sell them anymore.

http://www.amazon.com/Extech-RF40-Ba...ry+acid+tester

[zman-az]

How old are your batteries?

[GA Navigator]

I'm no expert but I think the alternator output voltage sounds too high.
The regulator failed on my tractor and the battery exploded. I checked the voltage output and it was 15 volts.


1994 Holiday Rambler Navigator
Cummins 8.3
Allison MD3060

[87Rockwood]

Use the same meter to make all measurements-you may be chasing your own tail so to speak. The Scan gauge II was not calibrated at the same factory/tech as the "multi meter" By the way which meter do you have?

[twinboat]

I agree with using a good accurate volt meter for checking volts, but in this case we can't ignore the OP, who said that the batteries were EXTREAMLY HOT and BOILING real good.

[Tom Lopez]

Batteries are Interstate GC2 6V 232 May 2012
Multimeter is Harbor freight $8.00 kind.

Today's Test results for your reading pleasure and consideration:
(24 hour time)

1. 0815 - not plugged into shore power and engine off:
Left Bat 6.26 Right Bat 6.20 Combined = 12.45 Chassis Battery 12.60
House monitor shows Main Bat 12.59 Aux Bat 12.45

2. 0820 - Plugged into shore power (Pd9260 converter charges at 13.6)
Leff Bat 6.6 Right Bat 6.5 Combined = 13.1 Chassis Battery 13.3
House monitor shows Main Bat 13.33 Aux Bat 13.35

3. 1200 - Reading after being plugged in for 3 hours 40 minutes
Left Bat 6.79 Right Bat 6.57 Combined = 13.36 Chassis Battery 13.44
House monitor shows Main Bat 13.42 Aux Bat 13.43

4. 1230 - Unplugged Shore Power - Readings after resting 30 minutes:
Leff Bat 6.39 Right Bat 6.32 Combined = 12.72 Chassis Battery 12.78
House monitor shows Main Bat 12.78 Aux Bat 12.68

5. 1235 - Readings at time of ENGINE START:
Left Bat 7.40 Right Bat 7.09 Combined = 14.50 Chassis Battery 15.07
House monitor shows Main Bat 15.03 Aux Bat 14.86
SCAN GAUGE II shows Volts 15.0 to 15.4 at start up 772 RPM

6. 1245 - Both batteries are bubbling, Left faster than right.
Left Bat 7.31 Right Bat 7.03 Combined = 14.35 Chassis Battery 14.92
House monitor shows Main Bat 15.03 Aux Bat 14.86
SCAN GAUGE II shows Volts 14.8 to 15.0

7. 1310 - Batteries are boiling, left faster than right. Left temp is about 113 and right is about 105. Both are hot to touch. Can smell gasses.
Left Bat 7.07 Right Bat 6.90 Combined = 13.99 Chassis Battery 14.51
House monitor shows Main Bat 14.42 Aux Bat 14.33
SCAN GAUGE II shows Volts 14.2 to 14.6 at 601 RPM

8. 1320 - STOPPED ENGINE
Left Bat 6.61 Right Bat 6.45 Combined = 13.00 Chassis Battery 12.96
House monitor shows Main Bat 12.90 Aux Bat 12.86

All through this procedure chassis battery remained COOL, no heat at all.

I called Interstate and asked if batteries could show good but still be bad. They said unlikely. The hydrometer test and load test should detect that.

OK folks, I know one of you knowledgeable people know what my problem is. So what is it, I getting tired of looking.

HELP PLEASE, RELIEVE MY PAIN

[twinboat]

Alternator overcharging. Get it checked.

[OldToolmaker]

The KISS principle: Keep It Simple Stupid.

Now that I've made a new friend, I suggest that you check the connections to the Chassis battery.

FWIW, the bulk charge rate on the PD9260 is nominally 14.4V, and if you have enough battery or load to require more than 60A, the PD9260 will fold back the voltage to limit the current.

On the way out in left field theory of thought, do you have an inverter that could be powering the PD9260 when the engine is running?

If not then there is a problem in the battery connections so that the house batteries are seeing a higher voltage than the chassis battery.

By the way, the lead oxide in the battery plates swells when it is charged leaving less space for electrolyte.

The Brix Refractometer is a great way to quickly check specific gravity of a solution but you need a "master" solution to calibrate the refractometer.

[GA Navigator]

Originally Posted by twinboat

Alternator overcharging. Get it checked.

Yup



1994 Holiday Rambler Navigator
Cummins 8.3
Allison MD3060

[tropical36]

Recently replaced our house batteries while traveling because of boiling and assumed a shorted cell in one of both. All OK since and we're still on the road.
Having said that, they were 6 years old, so not much to lose and not really worth fooling around with a lot of testing and especially while on the road.

[Tom Lopez]

Took batteries in again today for analysis. Did all the tests again, load test, hydrometer test, etc. Everyone says batteries are good, good, good. They have a full charge and are like new. I put them back in the MH and started the engine and after a few minutes (5 at most) the left one starts to get hot and bubble real good. The right is not as hot but it too is bubbling. So after some consultation maybe a ground is the problem. I go clean all the grounds and try again, NO LUCK. I call the workhorse repair shop nearby and they also have no answer. Everyone seems to think batteries are good, alternator is operating within specs. No one can answer why coach batteries are getting hot and boiling but chassis battery is cool and normal.

Anyone in RV land care to make any more guesses??

[l1v3fr33ord1]

Tom-

This is probably a dumb question, but how are the alternator and house batteries interconnected?

Dumb question #2: If you break that connection, does the problem still occur?

Mark