Swapping a Trace Xantrex Inverter for a Magnum in a 2004 Monaco Signature

[shootist]

Originally Posted by pwhittle

Shootist,

Are you talking about the Xantrex or the Magnum?

Paul

On your magnum or a new xantrex. There is no ground for the monaco battery setup other than at the ground lug by the inverter. The chassis grounds to the lug also. Either the inverter lug goes to both with two 4/0. Or the ground lug has to go to both the inverter and the chassis.

[Monaco Wolfy]

Xantrex has two negatives. One grounds directly to the neg. battery post. The other is grounded to the frame. When installing the Magnum, both battery ground and frame ground connect to the neg. post on the inverter. Magnum support also said to run 4/0 in place the cooper grounding wire to frame. All this grounding is made easier by mounting a neg. bus near the inverter. Also, if your 4/0 cabling is 5 to 10 feet long, you must x2 your 4/0 as shown in the Magnum installation booklet. And over ten feet is not recommended at all.

[shootist]

Older xantrexs had 2 grounds, new ones don't.

[vito.a]

Originally Posted by shootist

Older xantrexs had 2 grounds, new ones don't.

The older Trace inverter has two negative 12v attachment lugs. The one on the front is from the house battery negative terminal, and one on the side has a short cable routed to the main frame rail.
The one on the side to the frame rail provides the main ground for the entire house 12v system. Monaco does not ground the house battery system in the battery box area.

When you install a Magnum inverter it does not have the ground lug on the side. To replace it, you can run a 4/0 ground cable from the frame ground lug to either the front of the Magnum inverter negative battery lug (this would make two negative cables attached here and the plastic cover will not fit), or you can route a new cable from the frame rail ground lug to the main battery junction box up near the front of the compartment (this is about a 3' run).

If you are converting from a Trace to a Magnum and did not purchase a longer 4/0 ground cable, you can temporarily use a jumper cable to provide a ground.

Wolfy, finding the gray generator run sense wire is tough. I was lucky to have the Ridge Creek Auto Gen start with a run sense wire to it.
You can find the run sense wire at the generator, at the drivers generator start switch, or the bedroom generator start switch.
If your coach has the small wire bundle routed to the Trace inverter for AGS, I would look for a taped off gray wire back inside the bundle. Maybe you will get lucky.
Hope this helps.

[pwhittle]

Originally Posted by shootist

On your magnum or a new xantrex. There is no ground for the monaco battery setup other than at the ground lug by the inverter. The chassis grounds to the lug also. Either the inverter lug goes to both with two 4/0. Or the ground lug has to go to both the inverter and the chassis.

On our 2005 Signature a long -ve cable from the chassis batteries goes to the starter, with a second shorter cable to a different lug on the frame from the house ground lug, about 10 feet away..

We changed that to a shorter cable from the -ve side of the chassis batteries to the frame in place of the long cable to the starter. The short battery from the starter to the frame remained in place. We did not really see any change in the cranking over of the engine,

Originally Posted by vito.a

When you install a Magnum inverter it does not have the ground lug on the side. To replace it, you can run a 4/0 ground cable from the frame ground lug to either the front of the Magnum inverter negative battery lug (this would make two negative cables attached here and the plastic cover will not fit), or you can route a new cable from the frame rail ground lug to the main battery junction box up near the front of the compartment (this is about a 3' run).

If you are converting from a Trace to a Magnum and did not purchase a longer 4/0 ground cable, you can temporarily use a jumper cable to provide a ground.

I installed the BMK next to the inverter and connected the -ve cable from the batteries that went to the front lug on the Xantrex to the battery side of the BMK shunt.

I ran a cable from the ground lug on the frame to the load side of the shunt and ran a cable from the load side of the shunt to the -ve post on the front of the Magnum. I was able to reuse the original cable that ran from the frame lug to the side of the Xantrex and cut it to length and put new lugs on it. I ended up with about 6” left over.

I certainly have more than 5 feet (I guess 15-20 feet) from the batteries -ve to the BMK plus the same for the batteries +ve to the inverter front +ve post.

All cables are 4/0.

I understand that at 125A charging there will be measurable voltage drop over even 4/0 cables and that the voltage drop will be less as the current drops. I assume the inverter engineers allow for that in the charge algorithms, but do not know for sure.

I do not understand why the inverter designers do not just run a pair or signal wires back to the +ve and -ve posts of the batteries so they can measure what is reaching the batteries and compensate for any voltage drop in the cables.

I will try to take some measurements and see if there needs to be any adjustments in the programming.

Paul

[shootist]

Originally Posted by pwhittle

On our 2005 Signature a long -ve cable from the chassis batteries goes to the starter, with a second shorter cable to a different lug on the frame from the house ground lug, about 10 feet away..

We changed that to a shorter cable from the -ve side of the chassis batteries to the frame in place of the long cable to the starter. The short battery from the starter to the frame remained in place. We did not really see any change in the cranking over of the engine,




I installed the BMK next to the inverter and connected the -ve cable from the batteries that went to the front lug on the Xantrex to the battery side of the BMK shunt.

I ran a cable from the ground lug on the frame to the load side of the shunt and ran a cable from the load side of the shunt to the -ve post on the front of the Magnum. I was able to reuse the original cable that ran from the frame lug to the side of the Xantrex and cut it to length and put new lugs on it. I ended up with about 6” left over.

I certainly have more than 5 feet (I guess 15-20 feet) from the batteries -ve to the BMK plus the same for the batteries +ve to the inverter front +ve post.

All cables are 4/0.

I understand that at 125A charging there will be measurable voltage drop over even 4/0 cables and that the voltage drop will be less as the current drops. I assume the inverter engineers allow for that in the charge algorithms, but do not know for sure.

I do not understand why the inverter designers do not just run a pair or signal wires back to the +ve and -ve posts of the batteries so they can measure what is reaching the batteries and compensate for any voltage drop in the cables.

I will try to take some measurements and see if there needs to be any adjustments in the programming.

Paul

Why do you have a 4/0 cable to the frame of the inverter? A solid copper like you have on a house ground post is what's normally used. Bmk is a battery management I assume, the shunt is just used for amps and voltage measuring? I didn't like the idea of loading two huge cables on the inv- lug so I ran the battery cable ground lug to the chassis ground, and the other to the inverter from the battery cable ground lug. You need the bmk in line just as the old xantrex had internally. There are a few inverters that have external voltage sampling. Important for lithium systems, not so critical for lead acids.

[pwhittle]

Originally Posted by shootist

Why do you have a 4/0 cable to the frame of the inverter? A solid copper like you have on a house ground post is what's normally used. Bmk is a battery management I assume, the shunt is just used for amps and voltage measuring? I didn't like the idea of loading two huge cables on the inv- lug so I ran the battery cable ground lug to the chassis ground, and the other to the inverter from the battery cable ground lug. You need the bmk in line just as the old xantrex had internally. There are a few inverters that have external voltage sampling. Important for lithium systems, not so critical for lead acids.

I reused the existing copper wire to the frame of the Magnum. Looks like 8AWG.

I followed this wiring diagram with the the DC negative distribution going to the chassis frame.



And now that I look at this drawing again, I see that the BMK is looking for direct connections to the battery. I have them terminated at the inverter end of the cables. I will suspect that should be direct to the batteries themselves.

Paul

[shootist]

That's nice, you are monitoring the voltage at the batteries and at the inverter.

[OldBeaver]

I will be going through a similar process with my DP RV as well.
Currently it has a Heart 2000W modified sine wave inverter.
I am planning on going lithium and with. Magnum 4024 inverter, so 24V and 4000W.
I am going up to 24V because I plan on installing solar on the roof.
I will probably relocate the batteries and the inverter to inside that coach. The batteries are currently mounted in an exterior compartment on a slide out tray. The inverter is in a compartment that's part of the engine bay and under the bed.
I am going to be replacing the couch inside the RV. It is an horrible home made contraction that one of the previous owners put in.
I plan on making my own with custom storage underneath. This will give me the opportunity to create a place for the batteries and the inverter in a much more sheltered environment.

[vito.a]

Old Beaver, what's your plan to step down the 24v to 12v for the coach systems?

If you use an MPPT solar charge controller you can stay with 12v batteries and still wire your solar panels in series for higher voltage to the charge controller. It will then charge the batteries at 12-14v.

[Al Brooker]

Originally Posted by vito.a

The older Trace inverter has two negative 12v attachment lugs. The one on the front is from the house battery negative terminal, and one on the side has a short cable routed to the main frame rail.
The one on the side to the frame rail provides the main ground for the entire house 12v system. Monaco does not ground the house battery system in the battery box area.

When you install a Magnum inverter it does not have the ground lug on the side. To replace it, you can run a 4/0 ground cable from the frame ground lug to either the front of the Magnum inverter negative battery lug (this would make two negative cables attached here and the plastic cover will not fit), or you can route a new cable from the frame rail ground lug to the main battery junction box up near the front of the compartment (this is about a 3' run).

If you are converting from a Trace to a Magnum and did not purchase a longer 4/0 ground cable, you can temporarily use a jumper cable to provide a ground.

Wolfy, finding the gray generator run sense wire is tough. I was lucky to have the Ridge Creek Auto Gen start with a run sense wire to it.
You can find the run sense wire at the generator, at the drivers generator start switch, or the bedroom generator start switch.
If your coach has the small wire bundle routed to the Trace inverter for AGS, I would look for a taped off gray wire back inside the bundle. Maybe you will get lucky.
Hope this helps.

Great writeup Vito. I'm currently replacing my Xantrex RV3012GS Inverter with the new sine wave Xantrex and I'm still confused as to what to do with the 4/0 cable that was connected to the chassi grounding lug on the old inverter. Should I connect it to the negative battery lug on the new inverter (which would be real easy) or should I pull it in to the battery box and connect it directly to the negative terminal on the chassis batteries? Is either way better?

[shootist]

Originally Posted by Al Brooker

Great writeup Vito. I'm currently replacing my Xantrex RV3012GS Inverter with the new sine wave Xantrex and I'm still confused as to what to do with the 4/0 cable that was connected to the chassi grounding lug on the old inverter. Should I connect it to the negative battery lug on the new inverter (which would be real easy) or should I pull it in to the battery box and connect it directly to the negative terminal on the chassis batteries? Is either way better?

Al, you have two ground lugs near your inverter. One is the chassis ground welded to the coaches frame, on the right of the old inverter. The other is the isolated ground from the batteries, next to the positive from the batteries. Run one 4/0 from the battery ground lug to the inverter lug and another 4/0 from either, the battery ground lug to the chassis ground lug,....or from the inverter ground lug to the chassis ground lug. I chose to have just one wire on the inverter lug and ran the chassis ground to the battery ground lug.

[vito.a]

I agree. You should have a 12v junction box (with both positive and negative) near the front of the same compartment your inverter is located. Make up a new 4/0 cable and run it from the negative terminal in the junction to the frame groung lug.

[Al Brooker]

Originally Posted by shootist

Al, you have two ground lugs near your inverter. One is the chassis ground welded to the coaches frame, on the right of the old inverter. The other is the isolated ground from the batteries, next to the positive from the batteries. Run one 4/0 from the battery ground lug to the inverter lug and another 4/0 from either, the battery ground lug to the chassis ground lug,....or from the inverter ground lug to the chassis ground lug. I chose to have just one wire on the inverter lug and ran the chassis ground to the battery ground lug.

Thanks Shootist. It sounds like your rig is setup a little different than mine. I have no chassis grounding lugs in the inverter bay of my 2000 Executive. the 4/0 grounding cable that was attached to my old inverter disappears up into the frame and I can't find the other end. I assume this is the chassis ground welded to the frame somewhere. It sounds like you're saying I can either connect the loose end of this cable to the inverter negative post or to the battery negative post. There's no way I can pull this cable back to the battery box so I would have to install a new cable if I have to ground the chassis directly to the battery negative terminal. Please see my crude diagrams below. Sorry, I just dread powering everything up and having an improper ground or frying something.