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Topic: Chassis Battery Compartment Refresh (Read 1168 times) previous topic - next topic

Chassis Battery Compartment Refresh

I'm going to break this into a couple of posts so its not so long and so I can actually have the time to write things down.

First starting with what we had and what we wanted to address.

1) 20241208_153608.jpg Proximity of fuel filter to the CAC inlet tube.  When the filter was updated it ended up closer to the CAC than the original and I wanted to slide it down the rail just a bit (for now).  Also the air force one Ping tank is mounted transverse and in an area I wanted to make some updates.

2) 20241208_153616.jpg Some of the wiring / air lines routing/securing was not great

3) 20241208_141028.jpg We had s l o w cranking on the starter, the engine would start but often set the check engine light due to low voltage (code 251 / Power Supply / Invalid Data).  Using the boost did prevent that.  Improving the battery cabling is on the list. 

20241208_153524.jpg Looking at the existing battery cable wiring, all the connections are on (2) frame mounted single point power posts.  In the picture the negative post is up top and positive one at the bottom. (5) cables go the posts but there are only (4) lugs as one of them is a pass though / union lug. 

As you walk through the stack up of lugs there are a few not great points. 

20241211_120644.jpg The first lug has serrated faces which really has nothing to bite in to, so IMO it reduces the contact area.  That line runs down from one side of the boost solenoid, it allows connection to the alternator and when the boost switch is on, to the coach battery's.

The next lug is that union lug, one side goes directly to the starter and the other to the battery bank.  This seems good as it allows a direct connection from the starter to the battery bank  Looking at the picture you can see (4) indents and (4) protrusions in that union lug face, kind of looks like die press marks.  20241223_151601.jpg Those 4 protrusions are the part that contacts the serrated lug, not a great connection.

20241216_133846.jpg 20241216_133828.jpg Another not great connection is the battery lug (on that union cable) where it attaches to the battery bank.  The battery bank cable ends in what I would call an accessory post, something that you would attach an accessory like a winch.  Anyway the contact area of the lug to that  post is limited, and IMO not acceptable for pulling 1000 cranking amps.  You can see in the picture how little was actually in contact.

The next lug on the stack goes to the foot of the bed to a 90 amp fuse and then on to the front of the coach to the ignition relays and rails.  This connection seems fine.  The last connection is the one with all the wires, I did not chase those wires but assume the go to the ECM and perhaps the 12V panel at the foot of the bed.  Again the connection looks fine.

4) The engine batteries did test OK but on the low end so an upgrade to consider.

5) Wanted to add a battery shutoff and possibly a battery monitor/shunt.

Done with the wants/needs, next post will be what we got done.
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"

Re: Chassis Battery Compartment Refresh

Reply #1 –
Quote from: steve –
Another not great connection is the battery lug (on that union cable) where it attaches to the battery bank.  The battery bank cable ends in what I would call an accessory post, something that you would attach an accessory like a winch.  Anyway the contact area of the lug to that  post is limited, and IMO not acceptable for pulling 1000 cranking amps.  You can see in the picture how little was actually in contact.
Great post as have all your upgrade posts have been.  I am especially interested in what you use to replace that battery lug.  I have long thought about the identical post on my coach and how it seems inadequate but have not sought out a better solution.  I recently replaced my starter with a geared starter and that improved the cranking but still is not what it should be.  I look forward to what you come up with. 
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Chassis Battery Compartment Refresh

Reply #2 –
Steve, you were lucky to get the nuts off those studs. Mine just twisted the stud in the holder. I removed each one and used a socket on the back to remove the cables then had to return the new assemblies for being too short to get all the cables on. Finally got 2 long enough for all the cables including adding one extra cable to the starter.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Chassis Battery Compartment Refresh

Reply #3 –
I was equally unhappy with my battery configuration so I decided to go with the buss bar solution.    And along with that I wanted a way to cut power to the chassis battery's so I found a high amp cut off switch.  1500 amp for 5 seconds, that should be enough since the 8.3 starts immediately. Fingers crossed.
  The wing nut battery connections may not be good enough so I'll be keeping an eye on them.
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Chassis Battery Compartment Refresh

Reply #4 –
Quote from: craneman –
you were lucky to get the nuts off those studs.
20241212_132124(1).jpg The positive one came off with no problem, the negative one just spun.  I was able to get a thin wrench (Hyper Tough 8-Piece Thin Wrench Set) under the lug stack to secure the lower nut and then it came apart.  Amazingly the (4) self tapping screws that mounted the posts to the frame came out, I felt for sure the heads would twist off.

Quote from: Bob & Sue –
I was equally unhappy with my battery configuration so I decided to go with the buss bar solution.    And along with that I wanted a way to cut power to the chassis battery's so I found a high amp cut off switch.  1500 amp for 5 seconds, that should be enough since the 8.3 starts immediately. Fingers crossed.
The wing nut battery connections may not be good enough so I'll be keeping an eye on them.
I seriously considered doing what you show but could not find battery connections that I was happy with, what you have look very good.    What I like about that setup is you are using standard lug lug interconnect cables that you can get anywhere, easy to maintain / fix  ^.^d
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"

Re: Chassis Battery Compartment Refresh

Reply #5 –

Steve, these military batt. clamps seem to be much better option. Jim.  Amazon.com: 1 Pair, Military Battery Terminal Connectors, Car Heavy Duty...

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Jim and Dona
2002 U295 36'
Lily, blue healer. Our fury person
Manx mid travel Ecotec turbo
2022 Bronco badlands Sasquatch
Trail 90 and 110cc

Re: Chassis Battery Compartment Refresh

Reply #6 –
Quote from: fourdayoff –
Steve, these military batt. clamps seem to be much better option. Jim.  Amazon.com: 1 Pair, Military Battery Terminal Connectors, Car Heavy Duty...
I do like those connections so i threw them into the cart.  I'm not sure how to check the wing nut connection for amperage loss but spread over 3 batteries ???
As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Chassis Battery Compartment Refresh

Reply #7 –
Long time no post... I did a chassis battery refresh some time ago with two bus bars and a HD Blue Sea battery switch. I use just one 8D AGM battery and it has been adequate. I have two 300AH LifePO4 house batteries and I occasionally use the boost switch to to top off the chassis battery while the coach is in storage. I keep the cassis battery switch off except to top of the the chassis battery. The AGM battery retains most of its charge easily for a month or more. The house batteries get charged via solar.
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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Chassis Battery Compartment Refresh

Reply #8 –
Group 31 batteries use studs. Since I needed to install new batteries when I got my coach and new ahead of time the battery cables had been stolen I went with the group 31 with studs and made all new cables. Never had an issue since.

Re: Chassis Battery Compartment Refresh

Reply #9 –
Quote from: dsd –
Group 31 batteries use studs. Since I needed to install new batteries when I got my coach and new ahead of time the battery cables had been stolen I went with the group 31 with studs and made all new cables. Never had an issue since.
I just bought 3 group 31's with both studs and posts on them from O'Reilly's. Had to widen the battery tray as they are 13" long.

1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Chassis Battery Compartment Refresh

Reply #10 –
20250104_112537(1).jpg Here is the updated compartment (for now :) ).

To improve the fuel filter location, I drilled and tapped new holes, so I could shift it down the rail.  It ended up just being a couple of inches, but the clearance is much better. I did not measure, but those frame rails must be a 1/4" thick, so have a good cobalt drill bit and use a drop or two of cutting fluid like Tap Magic. I tapped them as 5/16"-18 (drilled a 17/64" hole), again using tap magic and going slow; the last thing you want to do is snap a tap.

20241224_151638(1).jpg The ping tank was moved down and rotated 90 degrees. I added a metal plate below it for some protection. The air lines were rerouted and placed in split loom and cable guides.  There was quite a bit of excess, so I was able to remove some length once they had been rerouted.

The battery cabling was redone in several ways, taking direction from several others install pictures.

20241221_161946(1).jpg Added a mounting panel that holds buss bars, shutoff, and shunt.  Those components are connected together with double copper bars for plenty of capacity. The panel has a step that helps to keep the various connections on-plane.  The items used on the panel are:

Modified the pass-thru battery/starter cable to a standard cable that connects the starter to the new buss bar.  There was enough existing cable (3/0) to allow me to cut off the existing union lug and compress on a new FTZ Power lug: Tinned power lug battery Did this on both the +/- leads, there was enough slack and space that I could do this without disconnecting the cables from the starter.

20241216_124006(1).jpg Replaced the battery cables with new marine grade (tinned copper) cable (4/0) that end in a FTZ Power lug (not an accessory post). This lug and the above starter lug are located in the same center (and the only things) buss bar post. I considered using top post (military spec) battery terminals but could not find ones that I felt worked well with the 4/0 cable & those FTZ power lugs.

Added a rubber strip under the battery hold down to provide some compliance
 
20250104_112545.jpg The new buss bars are at the approx height as the original single points but turned 90 degrees. There was enough existing cable to reach the new location, but I would not move those points too far from where they were unless you want to run a new cable. The cables with the serrations / interlocks had the least slack (they connect back to the house batteries), so I could not replace those lugs. Instead, I sanded the serrations down a bit to increase the contact area on the flat surface of the buss bar.
 
20241224_151707(1).jpg Engine batteries were replaced with Optima Yellow Tops.  I remained with the simple / effective diagonally connected arrangement as seen in the first photo.  It is not the "perfect" setup as there can be slight differences in individual battery currents.  Using a single cable, I had to stay with 4/0 for each joint.  In the future, I'm considering going to an equal length cable / buss bar arrangement, then I could run 2/0 from each battery to the buss bar and 4/0 from there to the main connections.  Downside to that is, you have to deal with more, longer cables and additional buss connections.

With everything in place, we have the most robust starting since we purchased this project.  I feel the main issue was the battery cables and the use of the battery accessory post connection adding too much resistance.
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"

Re: Chassis Battery Compartment Refresh

Reply #11 –
Now spray all those nice new connections with Corrosion X or something similar.
Dave and Kelli
1997 U295 40' Build #5188 CSGI
1995 U240 36' Build #4621 SBID-SOLD
2006 Jeep Wrangler Rubicon