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Topic: Chassis battery bus (Read 689 times) previous topic - next topic

Chassis battery bus

I have always used the boost switch in starting our coach because using the chassis batteries (2) alone it seemed to labor a bit before starting.  At first, I suspected something might be wrong with the batteries, however, both are only about 2 years old and gave a good load test at MOT earlier this year.  While having our fuel lines changed at MOT I asked Keith to evaluate this problem.  He checked the batteries again and thought they were OK, but he did suggest cleaning the "bus" connections where all the engine cables attach to the chassis battery cables (on the frame behind the chassis batteries).  It took him a while to get it apart since the bolts were seized and had to be cut off.  The result (see attached) is that the engine now starts as it should without the boost.  Evidently, the corroded bus (am I using the right term?) added significant resistance to the starting circuit.  I am posting this since I was unaware of these connections and perhaps others are too.
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George Hatfield

  Never ever use World Line Motors of Nacogdoches for service!

Re: Chassis battery bus

Reply #1 –
These are power posts or studs.  Good ones will have a nut (wrench fitting) at the bottom of the post.  You probably will need a thin tappet wrench for this.  Then the outer nut will be easier to remove.

Many have actually added a pair of bus bars, one for plus, one for minus.  Each battery is connected to the bus bars.  Starter motor cables go directly to the starter motor.  Another set of cables connects to the power posts.  A switch in the negative cable to the power post is a good idea.  A shunt after the switch lets you monitor the start battery condition.  You need to use big current capable bus bars.  BEP Marine Pro Installer 650 Amp, 3-Stud Heavy Duty Bus Bar.

This one has a bottom nut,
Blue Sea 2002 PowerPost terminal

This one does not, just don't over tighten.
BEP Marinco Pro Installer 50V, Single Stud

All of these studs and bus bars are long enough to connect three lugs (the recommended maximum number).

Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Chassis battery bus

Reply #2 –
Do you have a recommendation for a shunt? I found this one mentioned on youtube:

ttps://www.go2marine.com/Blue-Sea-Systems-DC-Current-Analog-Meter-Shunts_2?gclid=EAIaIQobChMIxe-_1puV5QIVhJ6fCh0DKAIMEAQYBCABEgLQovD_BwE

2000 U270 34' WTFE Build 5756 "Ole Red"
2014 Honda CRV
Washington, Vermont
Lady Lake, Fl,  Independence, VA
Former owner of 2002 U320, 2003 U320, 2005 U270

Re: Chassis battery bus

Reply #3 –
I like Victron components.  The Victron BMV battery monitor comes with a shunt, temperature sensor and is Bluetooth capable.  One without bluetooth is a bit cheaper, you have to look at the monitor.
Victron BMV-712 Smart Battery Monitor with Built-In Bluetooth
Victron BMV-702 Temperature Sensor

The BMV 700 keeps track of the battery in the same way, less money, no temp monitoring. 
Victron BMV-700 Battery Monitor

They might be a bit cheaper elsewhere but there is a discount at Bay Marine for the Forum community.  Call and place your order and ask for a Forum discount.  And they will actually help if you have questions.

The shunts are rated for 500 amps continuous and up to 1500 short term (like starting). 

Adding a switch to the negative side lets you disconnect the start batteries easily.
BlueSea make a good one. Blue Sea Systems model 9003E Marine Battery Switch
So does BEP Marinco. BEP Marinco Pro Installer EZ-Mount On/Off Battery Switch
These are rated about the same, use 4/0 cable to achieve maximum capability.

Make sure everything is clean and shiny when connecting cables and components.  Enhace conductivity and keep the corrosion and oxidation at bay with a terminal grease.  One little tub will last a lifetime (for most of us).
NO-OX-ID "A Special" Conductive Terminal Grease

If you need cables Bay Marine will make them in any size and length to order.
Custom 4/0 gauge marine battery cable
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Chassis battery bus

Reply #4 –
Roger,think he may mean the grounding cables that are grounded to the frame,mine are secured by a bolt thru the frame,George
do you mean the positive or negative cables?
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Chassis battery bus

Reply #5 –
If all connections are nice and clean, you should NEVER need the boost switch unless a battery problem, etc. I have posted several times about the boost switch being a crutch and masking a starting system problem. Yours is a prime example of a fault in the starting system making the boost switch necessary. If the Cummins factory says an engine will require X amps to start, then your start battery capacity should be that much will a little more for a hard winter and cable loss. No increased capacity will allow it to turn over or start any faster. What happens is that one day when the house batteries may be low and you have high resistance somewhere in the starting cables, you are stuck.

How many time on this forum has a member been stuck where the coach would not start? Lots! Almost every time, cleaning the battery posts, terminals has instantly cured the problem.  Good to know where each cable goes and what it connects with so the connections can be cleaned if necessary. Not a bad idea to run an extra ground cable directly to a ground point close to the batteries. Vibration and corrosion are the most common cause of problems.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Chassis battery bus

Reply #6 –
John44...  The pic of the terminals is not the best so I can understand the confusion.  There are two terminals, both isolated from the frame.  One is for the positive terminals of the chassis batteries and all the cables connected to it.  The other is for the negative cable from the starting battery and all the cables connected to it.  I know where the frame ground is located since John Haygarth and I cleaned it when I visited him in BC last summer.  On my coach, it is on the cross-frame member near the hydraulic pump side.

I've attached a "before" cleaning pic that shows the terminals better and how dirty they were.

George
The selected media item is not currently available.
George Hatfield

  Never ever use World Line Motors of Nacogdoches for service!

Re: Chassis battery bus

Reply #7 –
Looks like those examples Roger had would work,would definitely redo them.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Chassis battery bus

Reply #8 –
George, Swap the positive or negative cable to the other battery.  Better life for your batteries and more usable power.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Chassis battery bus

Reply #9 –
George this was Dons solution
Charging System project

George and Steph
1997 U270 36 Build 5081 "Honu"
1180w Solar 400A lithium all Victron house system
Motorcade 17670, SKP 128300, FMCA F459019
73 VW Camper, 79 VW Camper, 2363 Sunline, and an Arctic Fox 25P

Re: Chassis battery bus

Reply #10 –
Isn't his negative coming off the rear battery on the right side and the positive coming off the front battery on the left side the correct way for a setup?
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 bus

Reply #11 –
Quote from: craneman –
Isn't his negative coming off the rear battery on the right side and the positive coming off the front battery on the left side the correct way for a setup?

Yes.  All is good.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Chassis battery bus

Reply #12 –
A closer look at the picture on a bigger screen and George H's battery connections look right.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN