passenger battery boil over, volt gauge to zero.

[akshadow]

Today while driving down the road the check gauge light came on. eventually saw battery voltage at zero. Eventually stopped and looked under hook, nothing looked odd. Started and volt gauge was at almost 14 volts. drove for a few miles and happened again. Still did not notice anything under hood. After driving about 20 miles got home and saw the Passenger battery had spit acid around and felt hot.

Took both batteries out and checked with one of the resistance load testers I have and showed both batteries ok, voltage on passenger battery slightly higher than driver side.
Since I am in Baja, San Felipe, 86 degrees today. Usual resources are not available, did search of these forums and it appears most threads seem to think battery might be the problem, but tested ok. Have them both on a battery charge this evening to see if they equalize in volts when charged.

The other common problem identified was the possibility of a bad cable between the two batteries. What could the resistance be on this cable before it would cause a problem, or is there no way to test it without a load? will peal back some of the insulation tomorrow and look for corrosion, not sure if I could get a cable here.

Would it be ok or advisable to switch the batteries from side to side to see if problem goes away? Could get new batteries but hate to, they are Costco batteries and four years old Which does not seem old to me.

How do I look for codes ? which might indicate a problem but no check engine lights or other indicators of issues shown.

 

[seafish]

The ECM reads battery voltage on the drivers side and charges from the passenger side battery. The crossover cable is what connects the two and as long as all the connections are clean and tight, and BOTH batteries are in good condition, then there will be no overcharging problems. That means that if your batteries are in fact OK, you either have a bad/loose connection or the the xo cable itself is going bad. They can and do corrode UNDERNEATH the insulation, just a few inches back from the batteries. My advice is to remove, clean and then retighten EACH and EVERY battery/ground connection and ALSO slice back the insulation (parallel with the strands, not circumferentially) along the xo cable and check for corrosion of the actual wire strands a few inches back from each battery. If you see any corrosion at all, you should replace the xo cable with a new one. If it is OK, then simply wrap the insulation back on with electrical tape and reconnect all the cables. Also if at all possible I recommend checking the condition of each and every battery cell with a hydrometer instead of the simple load tester. Even one cell going bad can lead to overcharging problems.

 

[Tuesdak]

If either battery is below 12.6 volts replace them both. A cell generates ~2v so a 10.4 volt reading means a shorted cell of the 6 in a battery. A old battery will drag down a new one and sulfate it out for a short life.

Put a voltmeter on the batteries with the truck running. They should be the same voltage. Then you can measure voltage drop across the cables to check for a bad one. High resistance on a battery cable is hard to measure with ohms setting using a 1.5v battery of the meter. Under a load of 6 plus amps going through it to charge a battery resistance shows up as a voltage across the cable. Anything over 0.5v is a problem.

 

[Bob4x4]

You can just about bet the pass side batt is bad,The old style batt testers do not tell the whole story,If you continue driving it as is there is a very high probability the batt will explode

 

[akshadow]

Put both batteries on chargers last night and then before I went to bed, put a "battery tender" on each of them and this morning each battery showed fully charged. Applied the load tester to each battery and the load showed battery good and did not drop voltage below 12.5.
The end of the cable next to the driver side battery shows some corrosion on the end of the cable. Will try to find a replacement battery cable here in San Felipe but doubt I will have much luck, so will clean it good and test all points with my good meter. Have cheap hydrometer will test each cell. might not be the correct reading but should show up differences between cells.
Thank everone for suggestions, will reinstall batteries and carefully monitor. Might be able to find batteries here in town if necessary.

 

[seafish]

Have cheap hydrometer will test each cell. might not be the correct reading but should show up differences between cells.

^^^…let us know what you find after you test them.

 

[akshadow]

The hydrometer test on the passenger side battery did not have very much difference between the cells. The driver side battery had a difference in one cell that exceeded the "30" point threshold. Most cells were in 1.325 range. one cell was down in the fair cell testing area and approximated 1.230. both batteries tested as good on the load tester.
Am going to see if I can find two appropriate batteries here in town and put them in. not sure if really required but would feel more comfortable doing this and then monitoring the chargind.
had some corrosion on the end of the crossover cable, but replacement not available here. cleaned bolts through the positive terminals, some corrosion and minor erosion of bolt. Tested ground connections and positive cables from side to side and ohm meter did not read any resistance.

 

[Tuesdak]

The hydrometer test on the passenger side battery did not have very much difference between the cells. The driver side battery had a difference in one cell that exceeded the "30" point threshold. Most cells were in 1.325 range. one cell was down in the fair cell testing area and approximated 1.230. both batteries tested as good on the load tester.
Am going to see if I can find two appropriate batteries here in town and put them in. not sure if really required but would feel more comfortable doing this and then monitoring the chargind.
had some corrosion on the end of the crossover cable, but replacement not available here. cleaned bolts through the positive terminals, some corrosion and minor erosion of bolt. Tested ground connections and positive cables from side to side and ohm meter did not read any resistance.

Looks like you found the problem. However: "ohm meter did not read any resistance" Due to the size of the huge cables this is not a valid test. As noted above you have to test for a voltage drop with a larger current in the cable.

 

[akshadow]

need to have batteries in vehicle to do this test. want to start with new batteries if possible. still don't know if available here.

 

[akshadow]

Got two new batteries here in San Felipe, correct group and cold cranking amps.
Installed them and ran truck for about 20 minutes. Both batteries raised voltage at same rate and both ended up about 14.1 and were holding constant when I turned it off. Will drive it tomorrow and check it out with a longer run.
Hope problem is solved.

 

[akshadow]

With new batteries Checked battery voltage, started truck checked again, drove about 15 miles and checked voltage, turned engine off and checked again. In all cases batteries were within .05 volts of each other on a good quality meter. Hope problem solved as did not get a new crossover cable. Will order one and pick it up across the border when we go in a couple of weeks.
Old batteries, still holding charge and recording equal voltage and good on load test machine.
If anything changes will post again.
Thanks for the information and suggstions.