Rewiring Generator to Chassis battery bank

[96 EVO]

17 minutes ago, dandick66 said:

I think I need to better explain what I have and what I want to do.  My generator is connected to the RRB bus (chassis batteries) with a 2/0 cable.  There is another 2/0 cable running from that bus to the FRB.  I was thinking of running a new 2/0 cable from that stud on the FRB to the generator.  I would then have 2, 2/0 cables running from the RRB chassis bus.  The banks would not be connected unless I pushed the boost switch.  

Got it!

Thought you were planning on using house batteries from the rear, and chassis bank from the front.

 

May help, what you are considering.

[Tom Cherry]

21 minutes ago, dandick66 said:

I think I need to better explain what I have and what I want to do.  My generator is connected to the RRB bus (chassis batteries) with a 2/0 cable.  There is another 2/0 cable running from that bus to the FRB.  I was thinking of running a new 2/0 cable from that stud on the FRB to the generator.  I would then have 2, 2/0 cables running from the RRB chassis bus.  The banks would not be connected unless I pushed the boost switch.  

For background, the cable running to the generator is 2/0.  It was set up to start from the house batteries.  I moved the cable to the chassis batteries and saw no difference in the starting.  Tom mentioned about running a cable from the 4/0 FRB stud.  However, my coach has a 2/0 running from the chassis batteries to the FRB and a 2 gauge (not 2/0) running from the house batteries to the FRB.

I considered adding another battery just for starting the generator, then I came up with this thought.  What if I ran a 2/0 cable from the 2/0 stud on the FRB to the generator?  Then I would have 2, 2/0 cables forstarting the generator.  It would be cheaper and less maintenance than adding a separate starting battery. 

OK, like Ben posted, you could try that.  But, since you have a 2/0 and had problems after swapping from House to Chassis, my gut, plus my experiences say….FIND THE PROBLEM. Swapping the Positive from a deep cycle to a cranking should have made, IMHO,  a noticeable difference. 

The tried and proven method, which many here use and others find “cumbersome” is this….You need to measure the voltage drop, or lack thereof, from the first point….then at every connection or across every cable. Thus, get a spool of #14 stranded hookup wire.  You will need some alligator clip leads or make up one.

Use either battery. Assuming you have 50A, use the house.  Clip the hookup wire to the positive on the battery.  Run the other end and clip to the Negative VOM lead. Now, put your Positive lead on the stud where the positive 4/0 attaches….or the feed into the Buss.  Have someone start the Genny.  Read the VOM.  LOOK AT THE VOLTAGE.  You should NOT see more than a tenth…DROP….ZERO is the value.  

Next…..put the clipped lead (one that was on the battery), on the stud that you just measured….find the next connection….rinse and repeat.  You will find, assuming there is a voltage drop at a connection or in a cable WHERE the problem is.  Otherwise, it is a guess and folks do all sorts of rewiring….some work.  I did this.  Did not find my bad switch.  It vibrated and was good sometimes and bad others.  

BUT, when the Genny wouldn’t start, i jumped it….and did metering.

I assume you have a 10Kw. Before I did much more, clean the grounds in front and rear.  We have ALSO had several instances where there was internal corrosion in the cable and terminal.  You can’t see that.  But once you see a half volt drop across a cable, bingo….the issue.

That’s it.  BORING, but the only way to isolate a high resistance connection or cable…

GOOD LUCK…

[96 EVO]

35 minutes ago, Tom Cherry said:

 

  Swapping the Positive from a deep cycle to a cranking should have made, IMHO,  a noticeable difference. 

 

It actually does!

Until the temperature drops below freezing.

[dandick66]

2 hours ago, Tom Cherry said:

Use either battery. Assuming you have 50A, use the house.  Clip the hookup wire to the positive on the battery.  Run the other end and clip to the Negative VOM lead. Now, put your Positive lead on the stud where the positive 4/0 attaches….or the feed into the Buss.  Have someone start the Genny.  Read the VOM.  LOOK AT THE VOLTAGE.  You should NOT see more than a tenth…DROP….ZERO is the value.  

Next…..put the clipped lead (one that was on the battery), on the stud that you just measured….find the next connection….rinse and repeat.  You will find, assuming there is a voltage drop at a connection or in a cable WHERE the problem is.  Otherwise, it is a guess and folks do all sorts of rewiring….some work.  I did this.  Did not find my bad switch.  It vibrated and was good sometimes and bad others

I should only have to measure 2 locations since the cable runs from the rear bus directly to the generator.  I’ll clean/double check the grounds, too.  
Yes, I do have the 10kw.  
I’ll try to get this checked out before I head out of town this week.  Otherwise, it will be sometime next month before I can do any troubleshooting.

[Tom Cherry]

11 hours ago, dandick66 said:

I should only have to measure 2 locations since the cable runs from the rear bus directly to the generator.  I’ll clean/double check the grounds, too.  
Yes, I do have the 10kw.  
I’ll try to get this checked out before I head out of town this week.  Otherwise, it will be sometime next month before I can do any troubleshooting.

YES…but understand the process.  Clean the Grounds FIRST.

The troubleshooting technique is that you start at the battery….then go through every connection or relay or solenoid or wherever the “cables” are bolted or make contact… That ALSO includes the House Disconnect switches, if they are in the circuit. It is sometimes a PITA to get to the back or switches or contacts….but you have “isolate” or check the voltage drop at each point or device.  Study your prints…and the  follow the circuit on paper and then on the MH.

It is probably a connection….but possibly a cable…very rare….but happens.

Good Luck.  Let us know…

[Stephen D]

On 10/27/2023 at 5:20 PM, Tom Cherry said:

YES....that will be evident when you pull open or go into the battery compartment.  NOW...remember....no matter if you have to use a vehicle to jump off the engine or the genny (house bank), you ALWAYS need to turn OFF BOTH BATTERY SWITCHES....THEN ATTACH the Starting Battery (Car or whatever) OR Do the INTERNAL JUMPERING.,....That is critical...

YES....POSITIVE TO POSITIVE (from Each Bank) to Negative.  You have FOUR batteries on the HOUSE.... use the Front or REAR ones....

Since this seems to be a little unfamiliar....I took a page out of your manual.  Still suggest, that as you progress or want to understand, read BOTH the electrical session.

As the SAY...One Picture....10,000 key strokes....  OK...look at the marked up file.  The SOLID Black Lines are the MAIN JUMPERS between the Batteries.  So, any of the ones I marked are OK.  NOW, for your continued education.  See the smaller, grayed out ones between each set of HOUSE BATTERIES.  These commonly are KNOWN as the INTERNAL or the HOUSE Connectors...my terminology.  They connect one 6 VDC to another....thus the TWO, in SERIES are 12 VDC.  BUT the large Black Jumpers, that connect the Chassis to each other and the two "sets of 6 VDC" are the Cable or Jumpers that put the batteries or "set" in parallel.  That means you get BOTH batteries or "sets" in parallel.  The CURRENT from each is added.  SO, if you have 225 Amp Hours in a 6 VDC battery....that is the SAME for the two batteries in series or with the small gray jumpers.  BUT, when you put the TWO sets in Parallel, you have 450 Amp Hours of current.  Many folks don't know that....as they never had to "work with it", so if you knew that....just repeating....but it NOT, then helping you to learn.

Ben responded...as expected. and he is happy with his decision.  He is very experienced and knows how the entire system works and did his own rewiring.  I have the same MH and there is a great print...as well as easy to see cables....  BUT, for curiosity's sake, I went through your prints.  TOTALLY DIFFERENT...which happens.  You have ever piece of pipe and fitting detailed...  BUT there is no where, that I saw, the High Current Print showing the large fuses (presumably) that connect the Generator to the House Buss....  Also went through the Manual.  NO PICTURES or High Current Fuses listed for the rear.....  SO...I'm sure we have a LOT of experienced folks that could easily understand and trace circuits and move things around...  But, I can't find any prints to even offer, as you learn MORE, how you would do it.

That's my take....

JUMPERING HOUSE AND CHASSIS BATTERY DIAGRAM - 2009 KNIGHT...AND OTHERS.pdf 322.53 kB · 33 downloads

Hi Tom I’ve always had a problem starting my Genny on my 2010 dynasty if the house battery’s are not 12.6 it won’t start which is a pain if they start to go down wile travelling running the residential fridge but even though it’s messy I always jump it at the genny end connecting a jump pack to the cables on the genny I was going to add jump points to make it easier would you still recommend turning the batteries off wile I connect as I’ve never done that as I was up front off the coach

thanks Stephen D 

[Tom Cherry]

1 hour ago, Stephen D said:

Hi Tom I’ve always had a problem starting my Genny on my 2010 dynasty if the house battery’s are not 12.6 it won’t start which is a pain if they start to go down wile travelling running the residential fridge but even though it’s messy I always jump it at the genny end connecting a jump pack to the cables on the genny I was going to add jump points to make it easier would you still recommend turning the batteries off wile I connect as I’ve never done that as I was up front off the coach

thanks Stephen D 

@Frank McElroy PLEASE CHIME IN HERE.

Generally, and ESPECIALLY for your Kongsberg CCM Chassis, MY recommendation is that you NEVER hook up any Jumper Cables, whether from another Vehicle, a "Jump Pack" or even internally, with the Battery Disconnect Switches ON.  You should turn OFF the Disconnect Switches.  Then hook up the "JUMPERS". Then turn ON the Disconnect Switches. Then start or accomplish what you want.

If you are trying to recharge one bank....say the Chassis... You leave EVERYTHING as hooked up and let the Engine run for maybe 30 minutes to an hour.  That should restore a surface charge to the Chassis batteries.

THEN....turn off the device (Genny or Engine) that needed JUMPING. Then turn OFF the Disconnect switches.  Then REMOVE the cables or whatever. THEN turn back ON the Disconnect switches.

USUALLY, the Engine will start, but it is NOW SAFE to use the BATT BOOST switch.  Likewise, it is now safe to use the BATT BOOST to start the Genny.

That's MY RULE OF THUMB.  Overkill? Probably? Does it take a little longer? YES.  Do you eliminate the potential for shorting out a component? YES.

This is especially critical on the Kongsberg CCM Chassis.

 

 

[Frank McElroy]

2 hours ago, Stephen D said:

Hi Tom I’ve always had a problem starting my Genny on my 2010 dynasty if the house battery’s are not 12.6 it won’t start which is a pain if they start to go down wile travelling running the residential fridge but even though it’s messy I always jump it at the genny end connecting a jump pack to the cables on the genny I was going to add jump points to make it easier would you still recommend turning the batteries off wile I connect as I’ve never done that as I was up front off the coach

thanks Stephen D 

If you are not able to maintain house battery power while driving, the root cause is your big boy not working to connect the chassis to house batteries so that the house batteries are charged by the engine alternator while driving.  Either big boy needs to be cleaned or the small control board in the RRB needs to be repaired..

This is actually a very serious issue on a Kongsberg chassis multiplex coach.  While driving the house batteries MUST be charged either by the engine alternator or the generator via the Magnum inverter/charger.  If driving at night with the lights on, eventually you will lose all house battery power and all dash and lights will go dead yet the engine will still run.  In your case until big boy is either fixed or bypassed you should always run the generator while driving.  Any time while driving, if house and chassis batteries aren't showing charging voltage, run the generator.

As for using a battery pack to jump start, just connect the positive lead on the battery pack to the house battery lug on the side post in the FRB (Front Run Bay) and the other side to ground.  The generator battery cable connects to that lug in the FRB.  No need to turn OFF the battery disconnect switches (which on most Kongsberg coaches won't power down the FRB anyway).

[Stephen D]

Thanks frank I’ve had the problem of the alternator not charging the house batteries from new and I just thought it was not supposed to because of the size of the bank I also through there was a problem from new with the big boy as when I pressed the dash jump switch nothing happened and the big bog would not disconnect unless I switched the batteries off at the disconnect switch as there’s no techs here in the uk I will probably need help to fix the problem  when I get the motor home out of to winter storage 

thanks again to all stephen D

[Frank McElroy]

5 minutes ago, Stephen D said:

Thanks frank I’ve had the problem of the alternator not charging the house batteries from new and I just thought it was not supposed to because of the size of the bank I also through there was a problem from new with the big boy as when I pressed the dash jump switch nothing happened and the big bog would not disconnect unless I switched the batteries off at the disconnect switch as there’s no techs here in the uk I will probably need help to fix the problem  when I get the motor home out of to winter storage 

thanks again to all stephen D

First follow the big boy cleaning procedure.  Since you hear it engaging, likely all it needs is a good cleaning of the interior contacts.

 

[Stephen D]

Thanks frank my first job of the season 

Stephen D