1973 Winnebago brave - battery wiring

[Art]

So I went to reinstall the 3 batteries in my Brave now that winter has finally left us, and found my hand drawn schematic of how it all connects had gone missing .You know the important papers you have that you put in that safe place...  And my backup picture on my smart phone can't be found .   Not a good start .

How hard can it be ?

Connected the chassis battery and she started right up !  Always good news !!!!

Now to the two coach batteries .  So there are two negative cables and two positive cables, along with a "jumper" cable for each positive and negative post to "tie" the two coach batteries together . One of the positives had a big clamp type thing on it, assuming it is some sort of fuse type thing but since the batteries are tied together did it really matter which positive post to connect to ?!   Doubtful so connected them all up and the lights inside the RV now all work  

Great right !!!!  Nope .There are still two thin cables left over . One is white and the other is black mostly with a small fuse like connector and a thin similar gauge yellow wire coming out of it .

My question is where do these two cables connect to and what are they got ?  They kinda look like ground wires but isn't that what the negative cables look after ? They seem to come from the same location but I can't trace them at this point . I have a schematic that is more a high level, that shows you can tie the coach batteries to the chassis battery for emergency starting, could it be related to the relay function for that ?

Either way I need help where to connect these last to cables .  Makes me a bit nervous if they are not connected properly. 

Thanks in advance for any help you can provide !

Thanks...Art

[postman]

As Labeled "Coach Batteries" these batteries need to be identical. One weak cell and it causes these batteries to constantly drain the state of charge. With a full fresh charge, check the specific gravity of battery fluid in each cell. (while you may not feel this is pertinent info. it is correct info.) You can do a load test which can take quite some time.

The image you posted is for reference and not accuracy. I need to photo my bank so you can see. But I will post the starter relay pic demonstrating the chassis ground (to the transmission.

[postman]

12 volt marine battery bank.

[Art]

Thanks for the pic. So looks like I do need to adjust my cabling to match your marine bank.

Confirming both batteries are identical - bought new last year - removed over the winter, stored inside and set to charge for 6 hours a couple times over that timeframe.

Then all that is left is to figure out what the two thin cables left over are for (one is white and the other is black mostly with a small fuse like connector and a thin similar gauge yellow wire coming out of it).

[postman]

I called it "Marine" because the group 27 batteries are not quite Deep Cycle, so I was told.

[Lakota Wolf]

When looking at marine batteries, Size isnt always a factor,, the amp hr rate is what needs to be verified,,,,,,,  BTW, the battery diagrams and schematics are great, thanks for sharing.

[postman]

Here's the sales page...

Risk on Craigslist

https://www.interstatebatteries.com/products/srm-27

[postman]

Okay Art, next is to locate your MOM and battery isolator, checking they are wired correctly. I modified my sliding battery tray so it is removable. There are two things 70s Chrysler never excelled, Altenators and Starters. So batteries save headaches or causes them.

[Art]

Thanks. I don't think any of the wiring outward from the batteries are suspect / incorrect. Everything seems to work properly. I have only had her a year and a half, and use of things like shower / stove / furnace have not been required.

I need to get her on dry solid ground - lots of rain here in Ontario the last little bit. So once I get her home on the driveway from the winter storage location, I will do some traces.

I will also post a MOM / isolator schematic I found - key to sharing good info amongst these forums. Unfortunately my companies firewall blocks this site - guess it has bad things happening - so posting attachments is a challenge.

Yes - the battery compartment / tray are a battle for sure.

[Art]

Mom