Chassis battery not charging and drawing when in use and plugged in

[RJSprinkle]

We have a 2017 Axis that we have put new batteries in and are dead after a day or two when the RV is plugged in and in use. We just installed a cutoff switch that is working. We would like to figure out why this is happening. We did several tests today. The house batteries are fine and work as expected when in use or store and plugged in or not. Without the cutoff switch the chassis battery will be dead, why would this be? Thanks in advance for any advice!

[aether_one]

Originally Posted by RJSprinkle

We have a 2017 Axis that we have put new batteries in and are dead after a day or two when the RV is plugged in and in use. We just installed a cutoff switch that is working. We would like to figure out why this is happening. We did several tests today. The house batteries are fine and work as expected when in use or store and plugged in or not. Without the cutoff switch the chassis battery will be dead, why would this be? Thanks in advance for any advice!

Without hands on troubleshooting I can't answer your question; too many possibilities from lights left on to a bad new battery.

[twinboat]

I own a 2017 Axis.

First, you need to leave the Use/Store switch ON for any battery charging. If in the store mode, nothing will charge.

While on shore power or generator, the converter/charger charges the house batteries thru the use/store solenoid.

When the house battery voltage rises to 13.4 volts the BIM senses this and closes its relay to charge the chassis battery.

If you have a volt meter, you can check the voltage at the BIM. Its in front behind the hood, on the right side behind the headlight.

With shore power off, there should be battery volts on both large terminals. One will = house voltage and the other will = the chassis battery.

If no chassis voltage, look for a breaker near the chassis battery it can be seen with the hood open.. They have a button that causes a small lever to pop out when tripped.

The breaker for the house battery is on the outside rear wall of the house battery tray,

Let us know what you find.

Here is a pix of the BIM and the Circuit breakers.

[RJSprinkle]

@trfyman
We made sure that everything we know of is off so that we didn’t believe there should be anything drawing the battery, but there still was, we have no idea what, thus the reason for installing the cut off switch. We bought good AGM battles for all. We took the chassis battery back out (no easy feat) and took it back. They said it was good but too drained for our system to charge it back up so they charged it. We reinstalled it and it works well so long as it’s not getting drained with this unknown draw. We don’t really know where to start as this is our first RV. Thanks for taking the time!

@twinboat
Thanks for the explanation if the system, that helps! We are completely new to RVing. We will check the voltage on the BIM tomorrow and if necessary check the breakers. I’ll post an update then. Thanks so much for taking the time for all this!

[HJLowell]

Must have for fast troubleshooting

Good luck.

[gatorb8]

Get yourself a clamp on dc current meter, with engine off, put meter in dc current mode and clamp it on the positive wire of the chassis battery. You can then read how much current is being drawn and start disconnecting chassis electrical items until the meter sees a significant reduction, that will be your faulty or “left on” item.....like a radio for example
This will require some electrical knowledge if it goes beyond the simple items to test
Good luck!

You can also start the engine and see how well the engine is charging your chassis battery with this setup, the current will reverse. For example, if you see -5 amps with engine off, you should see positive amps with engine on

[RJSprinkle]

The BIM has voltage to both terminals, the breaker is not tripped. We tripped it on purpose and there was still voltage to both terminals. Is that normal?

@gatorb8 we are not sure how to do the tests you exactly the way you indicate, maybe we don’t have exactly the right tools, but get the idea.

We did figure out that the fridge/freezer when in auto Mode and RV plugged in to shore power was drawing the chassis battery down. Is that normal?

The chassis batteries will only charge off the alternator or from the charger/maintainer we have installed. We plugged in to shore power, had the solenoid switch on USE so the batteries would charge, the house batteries were over 13.4 and the chassis batteries still would not charge. Does this indicate our BIM is bad? If so, do you just replace it with a new one or is there something better? From other posts I’ve read it sounds like it is an annual part to replace. We didn't have this problem the first year and a half we had this RV so we don’t think the wires could be mistakenly reversed, one scenario I also heard reported.

[twinboat]

Get the house batteries charging on shore power.

Now with volt meter on chassis battery or chassis battery terminal of the BIM, push and hold the Aux Start switch, on the dash.

The BIM should clunk and the chassis voltage should come up to house battery voltage as long as you hold the Aux switch.

If no clunk, check the small wires on the BIM. If it clunks and no raise in voltage, could be a bad BIM.
Its the first I've heard if one failing.

The fridge should only run from the house batteries. The fuse is in the fuse/breaker box. All power to that comes from the house batteries.
Open the back of the fridge and see if anyone ran any new wiring.

I opened my hood today, the breaker near the battery is not for the BIM cable. Its Probably for the relays in the outside compartment, under the driver seat.

[triplewide]

Looking forward to what you find after completing Twinboats suggestions.

Here is some additional info on the BIM:

http://www.precisioncircuitsinc.com/...ger-Rev7-1.pdf


The facts as I understand them:

Your system worked fine for 1 1/2 years prior to the new battery installation.

You are sure no wires are loose or connected incorrectly on the batteries and BIM.

With your coach plugged in, disconnect you installed closed, use/store switch on, coach batteries charge and engine battery does not.

Engine battery was extreemly discharged per test results.


My best GUESS: BIM is defective or not compatible with AGM batteries. You may want to contact the manufacturer and ask thier advice before spending money:

http://precisioncircuitsinc.com/

Here is a source for replacement if needed:

https://www.ltdrvparts.com/PRECISION...-10041-200.htm


If you are plugged in, you charger (converter) working, store/use on, self installed disconnect closed, then the BIM should maintain a minimun 80% charge on your chassis battery.

All the above conditions are being met because your coach batteries are being charged. If your BIM wiring is correct then the BIM should be maintaining the engine battery.

[Mahakal]

Hi
My MH was on shore power and would not charge the Chassis Battery. After checking fount a fuse trip by the house battery. Thanks