Chassis Battery Not Charging

[Paletinc]

Well it seems like when the shore power is connected to the coach (2017 Winnebago Vista LX 30T) I would have thought that the chassis battery would be at min. maintained by the coach charging system. The chassis battery will get charged when driving but no charging when the vehicle is off and connected to shore power
Looking for some input as to whether or not this is the way the coach works or maybe I have a problem with some charging system item.

[Morich]

YUP!
You've just run into one of the more common things to confuse us rV folks.
When plugged into power the converter will charge the coach batteries, then when we drive the coach and chassis are connected together so that the engine alternator charges both.

BUT when we shut down the engine there is a system which drops the connection between the two sets of batteries! On older RV, this is often called a "mode solenoid" but on newer, it can be called different names and one is "battery isolation manager (BIM) which is doing the same thing but using solid state parts instead of electro-mechanical like solenoids!

This is from a recent posting about the older style but your RV is the same except for the BIM replacing the solenoid.

Click this to get a better view!


Basic operation is coach battery is on one big contact and chassis battery on the other contact. I marked them red and green.
There is a wire LR that bring 12VDC down to the solenoid coil when we push the dash switch or start the engine, that 12v goes through the coil of the solenoid to make the contacts close, connecting coach to chassis and the engine alternator charges both as we drive!

I just took a look at your year, model and floorplan and it looks like that year may be on the divide as some show the older on sheet 4 and others newer on sheet 2 of this drawing.
https://www.winnebago.com/Files/File...016/191494.pdf

Both do the same but the older is what looks easier to seehow it works. We can also hear it clunk when the solenoid moves and I like that !
downside is that the older does tend to burn the contacts and go bad more often?

One way to check this is to look at the battery voltage of the coach battery, then start the engine or push the dash switch to see the coach battery jump to around 13+ when the alternator starts charging it!
But that also depends on the cables from the BIM or solenoid to the batteries being good and clean!
For help to ID the battery cables there were tape markers on them when new.

[Paletinc]

Good Stuff Richard -
I have been hard at trying to get this fixed and found docs in the owners file that shows I have the BIM, then finding it was another trick.
So far I have found lately that loose connections seems to be what's going on, so I will attempt to get at the BIM and twist and tighten things up and see if that gets it going. I had a loose wire on the Inteli Power converter and that came back on line after removing and re-installing the connections. I think the BIM has been an issue for a couple of years and just did not know about it until recently.
I will attempt to trouble shoot it before just replacing the BIM, now that I was able to find it.
I will update accordingly and thanks for the input!
PL

[l1v3fr33ord1]

paletinc-

BIM located in compartment on driver side aft of front wheels. It's behind the circuit breaker panel.

Chassis Electrical Box Assembly diagram, sheet 2 zone C-4

Chassis Wiring Installation diagram, sheet 1 zone C-6

Other wiring diagrams for your coach available through this link.

Please confirm the above applies to your coach, for yourself.

[creativepart]

My 2017 Adventurer had this issue and it was the failure of the BIM. The only fix was to replace the BIM.

One thing to know, the company that makes the BIM has changed the physical size and shape of the replacement part and to install a new BIM you need not only the new part but a separate mounting kit to install the new part in the OEM position.

I don’t know if the old style BIM is still in stock anywhere but if it was that would simplify things.

[Morich]

Getting down to specifics of EXACTLY which RV we are dealing with can be the real first step as it lets us go to the actully correct drawing.
But that can also make a new person feel like we are being just a pain as we need to get down as far as serial numbers and even what options were ordered on any specific RV.

A new person comes along and we really need to know what year, what model and floor plan but then we may need to ask if the serial number has a 7th digit of 1 OR is it 2 as a way to know whether it is an early year build or late!!!
Somewhere along the way, the person asking the question may get the feeling we are not wanting to help!

You gave us much of the needed info on first post and that let us start but we never got down to the serial number, which is where we know if you have a BIM or solenoid!
But that is really not important for the question of chassis battery charging while plugged in, as both systems disconnect when the engine is not running.

So we can answer the question without "harassing " you about the serial number!
But for your future info, looking at the 7th digit of your serial number may tell you if you are early or late build for that year!

Hint on using the drawings, if you get into it in the future?
They are generally divided into chassis 12VDC, coach 12VDC and 110AC, as the three big sections. But it can get confused at times as those are often conneected/disconnected, so where they put the thing you want may take looking!
Then for the physical location, going to the "installation" sections is the better place to get location drawings!
For looking at locations and finding a name for a part I don't know, the " Parts catalog" is an interactive setup on the post 2010 models and it is great for getting a look for details of things. Things are divided into sections like electrical and plumbing, letting us turn things over to study them as well as get the exact part numbers on a list at right.
https://catalog3d.winnebagoind.com/menu/Parts.htm

Lots and lots of info but finding it can take some time!

[Paletinc]

OK here is the info on the chassis 1F65F5DY9H0A0 short a couple of #'s.
I was able to get into the support site for Winnebago and pulled the needed diagrams for reference and today will be onto the troubleshooting. I was originally hoping for someone to come forward with the . . .silver bullet answer but after the research with the manufacturer I am now wondering if my problem with the house batteries not charging could have been related to the BIM also.
I have a much better understanding at this point than in the beginning and hope to narrow it down sometime today.

[Morich]

Sorry, I may have opened a can of worms on the serial number as I was not specific enough on questioning the 7th digit as it would be found in the RV serial number, not the chassis number.
That info would be on a label next to the driver in most Winnebago but if you have found you have the newer BIM, that likely solves the question and I might guess you will find you have a 2 in that 7th digit spot.
But if you have the BIM, that was what I was needing!

The older:


The newer with added parts and more complex:


See why I liked to working on the older better as things get more involved when they added a second battery disconnect switch as well as going solid state which is often something we have no info on what "magic" they do inside wherte we can't trace things without the engineers drawing of that part!

But for the connecting the two battery supplies togehter, it still has the same function and wiring. Wire LR from the dash area bring 12V to make the BIM operate and then uses FM as ground for that control circuit. It also indicates much the same battery cables but with the addition of mention of fuses in the cables.
I have not chased these fuses but I might expect them to be of the Mega-fuse type and located very close to the battery rack???

That leaves me thinking that if you don't see the battery voltages change when starting or pushing the boost switch, one of several things need to be checked.
One is if the BIM is good but also if the fuses and all the battery cable connections are good, clean and tight?
If the BIM is out where you can get to it easy enough, I might check the voltages leaving it but then the fuses and connections can be easier to get to for starters!

Hope for bad connections? They will be much ,much cheaper!

[Paletinc]

This will be interesting. . .I have completed the trouble shooting and found other issues, fortunately for me all has been repaired and we're back in the game.
The problem with the charger / converter ended up actually being a melted fuse, not sure how that happens but I was able to get the unit out and on the bench, tore it down, cleaned up the fuse holders installed new fuses and bench tested it and all is good.
Now to the BIM, looks like the area where it is installed has never been opened (I am the second owner purchased it May 2020) original owner put 10K miles on it so pretty much new. The problem was two loose wires, Ground wire and Dash Switch, the 5/16 nuts were never tightened from the factory. Seems it takes a special tool to do it and someone was just lazy or they forgot to get back to it, only finger tight and still had a gap between the nut and the I-Loop on the end of the wire on both wires. All things in the charging system have been temperamental at best since I acquired the unit, just never really noticed it?

Once all was put back together and tested on the Coach, within a few minutes the charger added the chassis battery into the charging so all three batteries were being charged and a few hours lated I checked again and the chassis battery was fully charged and not being charged anymore so out of the charging circuit.

The difficulty getting to the charger and the BIM makes checking them out the real problem, you just can not get to the fuses unless you remove the charger from the coach and you would need patients and persistence for this kind of work. . . . easy to fix when you can get your hands on these items. I have added a few picts for anyone with this model to understand the process.

[Morich]

Whoopee!
You make the second post by folks I've named "dedicated wizards" as they get the tough stuff done! Finding two in one day is very special!

Maenwhile looking at that fuse, I would guess it either did not get pushed in fully or the clip holding it is sloppy loose! what we are seeing is where the power was arcing as it jumped a gap! You get a mini arc welder...,.

Inventing that tool in the last picture gets you extra credit!
They probably have a special deep socket that has really thin walls and maybe even had it on an air tool that they messed up the pressure on!

Carry on and enjoy the tripping. You've earned it!

[Paletinc]

Morich, you are correct the fuse holders were loose and after cleaning them the holders needed a bit of a squeeze to tighten them up. I still wonder if charging a battery while in the coach with an external charger could have caused that condition? No doubt loose fuse holders are a problem but I wonder about a potential Equalization Mode of say 15v / 16v coming from an external charger while the batteries are still in the coach could be an issue. I won't do that again anyway

I wish the tightening of the nuts on the BIM could have been easier but its 10lbs in a 5lb box so just no room.

[Morich]

One of those big mysteries, I guess. Terrible to get something like nut removed , but they look like they did a nice job of labeling where the wires went!!

They may have the whole unit built on a bench with wires and all and then just drop the whole thing into place when building the RV??

I get the feeling we don't have the fully trained people onboard most places!

[Bobn1957]

Originally Posted by Paletinc

Well it seems like when the shore power is connected to the coach (2017 Winnebago Vista LX 30T) I would have thought that the chassis battery would be at min. maintained by the coach charging system. The chassis battery will get charged when driving but no charging when the vehicle is off and connected to shore power
Looking for some input as to whether or not this is the way the coach works or maybe I have a problem with some charging system item.

I installed a voltage sensing relay between the House battery and the chassis battery so that the converter/charger charges the chassis battery when the coach is plugged in. The VSR charges the chassis battery about one-half volt less than the house battery.

[AZ Ken]

I also have an LX30T. Where exactly did you find the BIM?

[Morich]

If the same on your year, it is found on the 2017 Vista here:



Check post 9 about the 7th picture down for more info on reaching it?

But if the chassis battery charging is the problem there are a number of easier and more likely things that I would check before digging this far!