Chassis battery charge

[Casey Lipe]

1995 Classic Motorhome can't keep chassis battery charged. After being plugged into 50amp circuit at campground, chassis battery is dead and have to jump off. Even tried auxiliary battery switch, to no avail. This was an on going issue for my father, which I have inherited. Earlier, I changed the alternator and still have issues. Not really comfortable that gauge shows a little below 14 amps and just turning on the blinker makes the gauge needle jump. Any ideas?

[Boom Sounds]

Your chassis battery sounds knackered to me. How old is it?

Disconnect the leisure batteries, charge the starter and once fully charged measure the voltage across the terminals. Leave a light power source on which takes power from the starter e.g.LPG detector or car stereo. Measure the current draw and take readings every hour. You'll soon discover if it is kaput..........or take it into a facility who can do a drop test on it. Frankly, if it is over five years old, I would replace it.

[mayco]

Plugging into shore power will charge your coach batteries only, not your chassis. You may want to check to see if you have some "phantom drain" on your chassis battery when the coach is sitting. You can do that with a simple multimeter. I had that problem a few years ago on my 310, once I located and corrected the drain no more problems. As Boom said, you may need a new battery too but you'll want to inspect for drain on the battery or you'll end up in the same boat with a new one.

[Boom Sounds]

Originally Posted by mayco

Plugging into shore power will charge your coach batteries only, not your chassis. You may want to check to see if you have some "phantom drain" on your chassis battery when the coach is sitting. You can do that with a simple multimeter. I had that problem a few years ago on my 310, once I located and corrected the drain no more problems. As Boom said, you may need a new battery too but you'll want to inspect for drain on the battery or you'll end up in the same boat with a new one.

Spot on, those phantom loads, such as the LPG detector will run you flat.......but once I got my charging system working correctly and replaced the starter with a high quality VARTA battery, I've never had another issue. My money is on a knackered starter battery. When you replace it, take time to undo (one by one) all the connections from the batteries to the battery solenoid and on to the heavy duty block on the frame rail. Clean them all with a wire brush. Once those are all clean and tight, you'll be in better shape and able to fault fix any further issues. Good luck.

[Boom Sounds]

When you clean up the connections, check the grounds. Have a look at a recent thread on the battery solenoid for a fault finding technique


Sent from my iPhone using Airstream Forums

[tevake]

A short term solution till you can find the problem, is to put a trickle charger on the start batt. While plugged into shore power.
Battery tender makes a compact single battery charger.

I've had two different Pros in to help find my phantom drain, and still looking.
Electrical diagnosis is not a strength of mine.

The low indicated charge level at the dash is a common issue in our rigs especially with the head/running lights turned on.

Does you start battery seem to be charging ok while driving?

Mike what did you find as the source of your drain?

All the best in finding the drain Casey, let us know what you do find.

Cheers Richard

[Boom Sounds]

Bad battery, poor grounds, dodgy battery solenoid or isolator. Check and fix one thing at a time in a linear fashion.


Sent from my iPhone using Airstream Forums

[tevake]

Ok. I'll fess up. I'm still using a charger to keep the charge up while parked.

Replaced batt, check
Cleaned contacts and grounds, check
Replaced battery isolator, check
Tested solenoids, check
Replaced converter, check
Brought in the pros, check

Still looking, check. 😰

Cheers Richard

[mayco]

Hey Richard, mine ended up being in the heater fan "high speed setting".

[martin300662]

I have to say, I am the same.....

Deltran Battery Tender gets plugged into both chassis and house batteries when Bella is not in use.

When I was in the US I had a 4 channel unit for Bella and my two bikes. In the U.K. I could only get a 2 channel model.

[mayco]

I have a master disconnect on both the chassis and coach batteries. If I'm in a situation where I need to leave the rig unplugged from shore power, I turn them off.

[mayco]

Here are the switches in my step well

[Boom Sounds]

It's the chassis battery.

Disconnect house batteries and see if it still happens. If so, leave them disconnected.

Test voltage at 12v distribution in coach (which should read zero)
If it is zero, you have pretty much established that it isn't the interior Airstream 12v system which has been lashed together
Measure current flow from battery
Disconnect the obvious candidate which are fridge, step, log detector, stereo - see if you can isolate what is drawing current. Remove one Chevy fuse at a time to see if you can isolate the problem circuit and current draw.
I had this issue when I first had the coach. It drove me mad. It was a combination of isolator which was faulty, fridge control wired to auto 12v system along with poor grounds.

Good luck
Nick

Hope this helps
Nick


Sent from my iPhone using Airstream Forums

[Casey Lipe]

Thanks guys, this gives me some direction to follow. All batteries are new, so whatever must be a phantom drain. The coach batteries stay up fine so def chassis problem. It's good to know that shore power doesn't charge chassis cause that really had me up a tree. I'll go to work and keep you posted.

[mayco]

Casey, set your multimeter to measure amps not voltage. Then disconnect your negative battery cable from the battery, clamp one lead from your meter to the bat cable and the other lead to a known good ground to frame. (All this with the ignition "OFF" and everything you can think of turned off) then look at the reading on your meter. If you have a drain it will read in amps on your meter. It shouldn't be much, like a fraction of an amp or a little more but you never know. So, if you see an amperage reading then something is drawing down your battery. Now pull each fuse on your chassis fuse block one at a time checking your meter after each one. You should see the reading on the meter drop when you've pulled the fuse that controls the circuit that is draining your battery. At that point you've isolated the battery drain to SOMETHING on that circuit........you'll then need to poke and test everything that's being fed off that circuit and find what device is draining your battery. Your radio/head unit should be on a coach circuit not a chassis so you might want to check that. Do those things and report back

Mike