Chassis batteries dead

[Jim Gill]

We recently developed a new chassis battery charging problem on our Beaver coach. Here's some background...
- 2006 Monterey w/60,000 miles
- New alternator: 11/11
- New Interstate chassis batteries: 02/13
- New Interstate house batteries: 04/13

Now the problem...coach had been running fine since new battery installations and then...
1. Coach was plugged into shore power for 2 weeks.
2. Tried to start diesel engine and it sounded like chassis batteries were dead...dash lights flashed, buzzers buzzed and the starter briefly stalled. Turned off switch and tried again...starter stalled briefly but then kicked off the diesel.
3. Drove 300 miles with Alladin engine and house screens both indicating charging at 13.9-14.1 VDC.
4. Plugged into shore power for 10 days...all things electrical including those items powered by the chassis batteries (radio, security panel, etc.) worked fine.
5. Tried to start engine yesterday and it sounded like the chassis batteries were dead again...dash lights flashed, starter stalled, etc. I activated the booster switch and the diesel fired up.
6. I drove 300 miles with both Alladin screens showing charging at 13.9-14.1 VDC. Arrived home, shut off engine and once again, it wouldn't start without the assistance of the booster switch.
7. I started the generator to see if the diesel would start with the electrical charging power from this source...with the generator running, I tried to start the diesel and as soon as I turned the switch, the generator quit, instantly!  

I suppose it's possible that one or both of the "new" Interstate chassis batteries are bad and aren't accepting a charge. They are maintenance free so there is no good way to check the acid level...I may need to take them out and do a load test. But I'm wondering whether this problem is linked to either the Big Boy Relay and/or the Bird module? I'm not completely clear on how these two components/systems interact and whether I may need to replace one or both of these items to correct my chassis charging (non-charging!!) problem.

Any thoughts?  And thanks in advance.

Jim  

[Joel Ashley]

Though suspicious of the BIRD, the first thing I'd check after so recent a battery change is the chassis battery post connections.  Like you, I'm dim about how all these things fit together and regularly have to resort to the manual, which often isn't fully helpful.  If your genset runs off the chassis rather than house bats, then perhaps drawing what was left of a high resistance current (due to corroded or loose cables) when you engaged the ignition, took sustenance power from the genset, causing it to stop.

I'm purely guessing, and am sure others here will chime in with more educated ideas.  But meanwhile, check the chassis battery post connections as a first resort, and use a meter if you have one to check their state of charge while plugged in, with the genset on only, with the engine running only, and after having sat with no charge source for an hour.  Those numbers may be helpful to fellow advisors here.

You might also locate and check the chassis ground point.  Your ignition is probably okay since the panel lights up and you hear the starter solenoid engage.

Joel

[Jim Gill]

Joel
Have you ever had an opportunity to locate the precise location of the chassis ground on your coach? I'll hunt for it tomorrow but thought it might speed up the process if you can point me in the right direction.
Thanks,
Jim

[Steve Huber Co-Admin]

Not sure on the Roadmaster chassis but my Magnum has a master ground connection on the bottom of the engine; passenger side.
Steve

[Joel Ashley]

You caught me off guard there, Jim.  We have similar coaches, but I've never had to find that ground location.  I would not expect it to be too far from the engine frame area, and I'd first check out Steve's idea.  Ours is a Roadmaster M chassis, which I've been lead to understand was basically their version of Beaver's Magnum, so he may be on the right track.

Wish I'd read your question earlier today so I could have looked for the connection in daylight;  see if you can follow the big chassis battery cable to any degree, which is where I'd have started.  Usually these grounds are pretty tight, but you never know.  I'd be more suspicious of the battery cables at their posts before moving to other possibilities.

Joel

[Robert Mathis]

I agree with Joel, this sounds like a problem with your battery connections, unless you have a dead short in one of your chassis batteries. When you tried to start the main engine with the genset running, it drew so much power that it shut the genset fuel solenoid off. A fairly simple way to check your batteries is to disconnect them from the cables and test each seperatll with your multimeter. If one is bad, it should show up immediately. When checking your battery cables, make sure to inspect the ends carefully. They can corrode inside the terminal end and loose the ability to transmit the power. I recently had to replace two of my terminal ends on my house batteries, they looked okay, but when I tugged on them, they came apart.

[Gerald Farris]

Jim,
It is fairly simple to check your "Bird" system with a voltmeter. When either battery bank is charging, either from the inverter or the engine alternator, then both banks should be charging. So you can check the voltage at the batteries at any time that either bank is charging to verify operation. If the "Bird" system is operating properly, you have one or more bad chassis batteries or bad cabling connections. From your description of the problem, I would have the chassis batteries tested.

Gerald

[Jim Gill]

Thanks for all of your constructive replies.
The moral to this story is to ALWAYS check the simple things as the root cause of a problem before worrying and fretting about more complex and more expensive sources. As a number of you suggested, I began, and ended, my troubleshooting with the confirmation of a good ground. It turned out that though all of the chassis battery connections APPEARED to be clean and tight, the battery ground connection which returned to the chassis ground was a bit loose. It was apparently tight enough to allow battery charging to occur since the chassis battery bank checked out as fully charged on my meter but it was not tight enough to carry the amperage load of starting the diesel engine. Once this connection was cleaned and tightened, all charging circuits worked properly and the diesel engine started repeatedly without any hesitation. So for now, problem solved!!!

Thanks again for all of the feedback.
Jim