Who can solve the MYSTERY?

[RVPioneer]

Originally Posted by Ivylog

I got 10 years out of a pair of Interstate 31s... got a deal on new ones in OR with no sales tax and I could keep them. I actually used them in a 24V machine for another couple years and then one for a couple more.

Good news. That’s what I put in 2 years ago.

Being in OR, no sales tax is nice. Particularly on major purchases.

[96Bounder1st]

Originally Posted by bamaboy473

ANSWER:

dead cell in one of the starting batteries.


I thought that once starting batteries started the Cummins, that they have nothing to do with the operation of the coach. Wrong.

The mobile mechanic seemed to think that a dead cell won't recognize charging, and it somehow reduced operating voltage to a level that messed with the transmission as well as killing electrical power to the engine.

That's a new one on me, but a new battery from Advanced (luckily just down the road because Camping World doesn't carry type 31S batteries )
Once installed the coach wouldn't start. A few minutes later, it started and has worked as new since then.

Thoughts on why a dead cell in a starting battery affected all electronics?

This is from past experience and may not be applicable here. I had a 3500 Super Duty with 2 start batteries as it was a diesel. When the one battery, one cell likely , went dead it would take all the output from the alternator and drain the other battery while running. The battery with the bad cell was very hot and the alternator was very warm also.
I made it to a garage while still running and replaced both batteries.

Just the experience I had and I never thought of it further. I had the problem repaired so did not care why it happened. Also had battery connections checked at same time as garage suspected a problem with them. They cleaned them but the battery tested dead so I carried on for another 4 years after that.

Glad you found it and are on the road again.

Terry

[bamaboy473]

Originally Posted by RVPioneer

Did you only replace the battery with the bad cell and leave one 8 year old battery in the coach?

What brand of battery lasted 8 years? I’d like to get those the next time I need chassis batteries.

Seems that I was lucky to find a group 31 at Advanced. They had only one and that one is 8 months old. Camping World doesn't even carry group 31s, so now that I'm home I'll source the second battery.

[bamaboy473]

Originally Posted by twinboat

I doubt you had a bad cell or needed a new battery. If you did, the new battery would have started the engine right away, and not a few minutes later.

Check the chassis ground cable of the chassis battery. Not just by looking, take it apart and look for corrosion.

Good idea. When I replace the second starting battery, I'll do a thorough check of the cables and connecting points.

[TomAndPeg]

bamaboy473:

Also check the battery isolation block.

On a previous coach of ours powered by an ISL-400, we had intermittent starting and other random electrical problems on the chassis side. Turned out one of the connections on the battery isolation block was arcing.

Just one more thing to eliminate as the culprit.

[Sonic]

Keep in mind that the transmission ECU is connected to the battery. A short in the battery can cause issues. I'm wondering if the delay in starting after the battery replacement was due to an electronic reset needing to take place after a short was detected.

[mymyst]

One bad cellwill kill the whole battery, and will tend to cause the condition as previously described, where the alternator charge capacity is being sucked dry by the defective battery, effectively depleting the good battery's charge as it struggles to keep the power up and flowing to the engine ECM, the tranny electronics, etc.....

I had exactly the same issue with facory original batteries which were weak from day one, after sitting on the dealer's lot for 9 mos. before I bought the coach. Other than being a little slow to crank from day one, the only other symptom I got was a jumpy transmission when shifting, and a low voltaage indication on the transmission shift pad right after the engine cranked, lasting just for a few seconds until the engine got fully up to idle speed.

I then started receiving intermittent "service wrench" icons on the tranny shift pad.....ok, time to call the professionals!

I learned that the coach OEM's specify the smallest battery capacity possible to the chassis builders, basically the bare minimum required to start the engine. The chassis provider would only warranty the factory original batteries for 12 mos. from the date the chassis rolls off the production line, due to the batteries being undersized (in reality), and having no control over when the chassis would be put into regular use and service.....ah well.

The big Allison 4000 is a bullet proof transmission when fed appropriately, but absolutely does not like low voltage at any point in it's life! So it was seeing a HUGE voltage drop when cranling up, and was trying to tell me it was not happy about it, giving jumpy starts and "low voltage" and "service now" messgaes...I thought I had a transmission going south with only 21,000 miles on it, not typical for this series of big transmissions! even if the main engine would crank. Once the engine charged up the batts for a while, the tranny would be "ok" to roll....

Once I learned all this and inspected the start batteries, I found one had a bad cell, and was beginning to "bulge". I replaced both batts out of pocket, and upsized them from a basic commercial 950 cca battery rating, to two 1100 cca heavy duty truck batteries....viola! no more slow cranking, and no more "cranky" transmission...everybody was happy again! And the big 15 litre cummins spun up on starting like I felt it should have all along!

Sorry for the long post, but thought soomeone might benefit from mypersonal education...it only cost mem $450 at Napa to buy the replacement batts, money well spent!

[bamaboy473]

The experience, and reading these posts, sure changed my learning curve about coach electronics. I thought that starting batteries were unique, and were in service only when the starting circuit was needed, then they just sit there and get trickle charged.

Now I know that they are a part of the coach electronics. I guess my advice to others would be that if you ever need to use AUX to start the coach under normal conditions, expect problems to start within hours of driving, so do yourself a favor and delay setting off until batteries have been checked.

[bamaboy473]

I'm about to order the second starting battery, and here's a question.
The one I bought is 950CCA, and they have another one that's 1000CCA. Can I pair those two, or am I better off with two that have the same CCA?

[Dick1142]

Originally Posted by jacwjames

If your coach has a battery disconnect for the chassis battery it may be going bad.

I was getting ready for a trip and had started/stopped my coach multiple times and then all of a sudden it would not start, no power to the dash. Checked my rotary disconnect and it was not passing power. Bypassed it until I could replace.


An intermittent connection where all power is loss would leave you dead in the water.

YES. HAD THIS HAPPEN TO ME. INTERMITTENT AND MISDIAGNOSED BY REPAIR PLACE AS ALTERNATOR.

[eliotrasi]

While in a town at a traffic light, engine died again, but this time there was nothing there to start the coach. Aux did not work again.

[bamaboy473]

Originally Posted by eliotrasi

While in a town at a traffic light, engine died again, but this time there was nothing there to start the coach. Aux did not work again.

If you're referring to my experience, that's exactly what happened. Alt and genset were putting out mid 14V, but seems like the dead cell kept batteries from being charged.

Is it possible that all 4 house batteries and the one good starting battery got drained within the course of about 60 minutes of driving?

[twinboat]

No, 1 hour of driving shouldn't kill 5 batteries.

My theory is that your chassis battery controls the boost solenoid and when you lost your chassis ground, it didn't connect.

[bamaboy473]

Originally Posted by twinboat

No, 1 hour of driving shouldn't kill 5 batteries.

My theory is that your chassis battery controls the boost solenoid and when you lost your chassis ground, it didn't connect.

I'm replacing the other starting battery tomorrow and will check the cables as you suggested. What's strange is that I did every cable about 6 months ago when diagnosing what turned out to be a main fuse. At that time the Main Battery Disconnect was dissected, too, and I really found no corrosion or green crud on anything.

Time to check again to be sure, though.