Magnum 3000W Inverter upgrade on a 2021 Interstate 24GT

[WeekendBob]

If anyone with a newer Interstate is curious if a larger Magnum 3000W inverter will fit under the front passenger seat where the current Magnum MMS1012 sits, I just installed one.

My goal in doing so was to:

1. Replace the non-lithium supported Magnum inverter and remote control that came from the factory (without relying on the dealer to do it)
2. Upgrade to a 3000W inverter to be able to run the microwave, A/C, or other high current appliances off the house batteries.

For the inverter I picked the Magnum MSH3012RV-L Hybrid. I won't get into all the pros and cons of the Magnum over other inverters. Several board contributors really like the Xantrex and there's a great thread here by mike2016 on installing the Xantrex in the same location. Mike's wiring diagram was also a big help for how to power the microwave off the inverter.

I also installed 2 additional Battle Born lithium batteries behind the drivers seat, bringing my overall total to 4. I made a custom box to house them, added a Victron shunt, and covered the box in black carpet to match the existing sprinter carpet.
Battery to inverter cables were upgraded to handle the load, along with the fuses.
The existing passenger seat outlet which powers the driver's seat BatteryMINDer chassis battery charger remains, but mounted against the seat base wall, and powered by the Inverter shore power "in" (thanks Mike for the suggestion).
The big red cut-off switch also remains operational and mounted against the seat base wall.

So In short, all functionality that previously existed is the same, with the following improvements:

1. I have 400Ah of lithium house battery capacity
2. I have 125 DC Amps of house battery converter/charging capability
   (which now includes a proper lithium charging profile)
3. I have 3000W of inverter power delivery capability
4. I have up to 25 AC Amps of continuous current capability for running either the microwave or A/C from the house batteries alone
5. I have up to 50 AC Amps of continuous current capability combining inputs from both the house batteries AND shore power or generator (this is the benefit of the Hybrid model) to support higher concurrent loads if necessary.

Some pics below


1. The original Magnum inverter. Not a very clean factory install if you ask me - lots of leftover sawdust, wire ends, and even a lost wire twist cap from the factory.




2. The newly installed Magnum MS3012RV-L Hybrid. A tight, but perfect fit




3. Test fit of my homemade battery box with 2 additional Battle Borns and a Victron Shunt




4. Another view, ready for the seats to go back in. (Note: I removed the Driver's seat so I could better route new interconnect cables from the factory Battle Borns located underneath the coach, below the passenger and driver's seats to the new battery box. I also re-wired the Victron DC-DC Buck boost charger with the negative to one end of the battery bank and the positive to the other end, as it should be. The factory had both positive and negative going to the same battery under the driver's seat.)




5. All done. Next I install an EasyStart for the AC which should be arriving today.

[toskeysam]

I also have a 3000 watt Magnum Hybrid. Mine is installed in the back of the coach with open frame protection. When it under load the fans really pump the air around. I’d be concerned about ventilation under that seat.

[WeekendBob]

Originally Posted by toskeysam

I also have a 3000 watt Magnum Hybrid. Mine is installed in the back of the coach with open frame protection. When it under load the fans really pump the air around. I’d be concerned about ventilation under that seat.

Yeah, I thought about that and have been keeping an eye on it. So far it hasn’t been an issue. Worst case I drill a few air holes in the seat base (without sacrificing the integrity) and maybe add a PC fan or two.

[Schmitte]

Very professional install!

[uncle_bob]

Hi

One possible mod:

You have a set of batteries outside in the cold (just like I do on the Classic). You have another set indoors where it's warm (again, just like my setup on the Classic).

In the case where things get cold, you can indeed run the set of 4 and let the BMS fight it out. You also could run the battery heaters on the outside set. The third option is to have a cutoff that lets you just run the inside pair. I did it with Blue Sea latching relays. There are other ways.

Bob

[toskeysam]

I've bragged too much about my 3000 watt Inverter/charger. One year out of warranty it decided to kick its feet in the air. It decided to croak while on the road...fortunately, at our destination.
I still have 400 watts of solar and alternator charging available so its not a show stopper.
The inverter side of the unit functions perfectly. The charger (and pass through) power have died. Went through lots of troubleshooting (fuses, circuit breakers, continuity, transfer switch, et al) and it seems to point to the internal relays in the unit.
Decided to go with a direct replacement as the quickest route to take. I may look into replacing those relays when I get the new unit installed...its not an easy task, but it is doable. (yay Youtube)
I considered switching vendors (to Victron), but its not easy to get cables made up at my location, and I don't trust doing high power connections with my amateur hands.
I'll add the unit to my "spare" inventory....along with macerator(s), water pump, various gages of wire and others.

[uncle_bob]

Originally Posted by toskeysam

I've bragged too much about my 3000 watt Inverter/charger. One year out of warranty it decided to kick its feet in the air. It decided to croak while on the road...fortunately, at our destination.
I still have 400 watts of solar and alternator charging available so its not a show stopper.
The inverter side of the unit functions perfectly. The charger (and pass through) power have died. Went through lots of troubleshooting (fuses, circuit breakers, continuity, transfer switch, et al) and it seems to point to the internal relays in the unit.
Decided to go with a direct replacement as the quickest route to take. I may look into replacing those relays when I get the new unit installed...its not an easy task, but it is doable. (yay Youtube)
I considered switching vendors (to Victron), but its not easy to get cables made up at my location, and I don't trust doing high power connections with my amateur hands.
I'll add the unit to my "spare" inventory....along with macerator(s), water pump, various gages of wire and others.

Hi

My vote would be for the Victron *if* you can fit it in the same location. I had to do some "customization" to the enclosure on mine to get it to fit in the Classic. Lots of un-needed aluminum in that enclosure One would *guess* this pretty much canceled the warranty on day one ....

One option for cables is to have them custom made and shipped to you. That's great for a 22" between X and Y. It's not quite so great for a "might be 20' or it could be 22'" sort of run.

Bob

[toskeysam]

Originally Posted by uncle_bob

Hi



My vote would be for the Victron *if* you can fit it in the same location. I had to do some "customization" to the enclosure on mine to get it to fit in the Classic. Lots of un-needed aluminum in that enclosure One would *guess* this pretty much canceled the warranty on day one ....



One option for cables is to have them custom made and shipped to you. That's great for a 22" between X and Y. It's not quite so great for a "might be 20' or it could be 22'" sort of run.



Bob

The Victron would fit, but I did the “ship cables in” last year and did not like 1) waiting for shipment, 2) the “oh crap, it’s too short” problems. That was for a relocation of main, solar, and alternator disconnect switches relocation. If availability of my replacement inverter becomes an issue (already had to switch vendor) I may have to suck it up and go Victron.

[uncle_bob]

Originally Posted by toskeysam

The Victron would fit, but I did the “ship cables in” last year and did not like 1) waiting for shipment, 2) the “oh crap, it’s too short” problems. That was for a relocation of main, solar, and alternator disconnect switches relocation. If availability of my replacement inverter becomes an issue (already had to switch vendor) I may have to suck it up and go Victron.

Hi

The Amazon "hydraulic" crimp tools do a pretty good job. They aren't perfect, but for $50 or so the price is right. Plan on practicing on a few parts before you do the "real ones". Obviously the cost of those extra terminals goes into the effective cost as well...

Bob

[WeekendBob]

I also was on the fence about buy vs. make the cables. I ended up making them and am glad I did. It provided a lot more flexibility since I’m sure some of my initial measurements would have been off as I adjusted cable runs, etc. I used the cheap (~$20) “hammer crimp” tool from Amazon. A bit crude but it worked fine with the 1-handed sledgehammer I already had....

[WeekendBob]

So, quick update on adding the A/C EasyStart. It was a surprisingly easy install, took about 45 minutes total. I forgot to take an “after” pic but there’s a before pic below of the roof mounted Dometic Pelican II with the cover off. The EasyStart mounts vertically in the corner which I circled in red, then it’s a matter of connecting 3 wires.



I got the new Bluetooth version so you can see the start amps and running amps. It was interesting to see that the first start was as high as 28 amps, but then after it “learned”, it was softer at 17 amps (see below). You can definitely hear the difference and now that I know how much quieter it starts, I probably would have installed one even if my initial goal was NOT running the A/C off the inverter.

[uncle_bob]

Hi

If you *do*decide to go with one of the Victron 3000 versions:

There is a cover on what is "normally" the top end. In a horizontal mount, that cover probably does not do much good. Right behind it are a couple of fans. I tossed the cover out on mine. It makes it a bit smaller and significantly improves the air flow. That reduces the fan on time / fan noise.

Air comes into the unit from the "bottom" (again as looked at when its wall mounted ....). If I'm guessing right these surfaces would be at the front and back of the passenger seat in the GT. Air would come in at the front of the seat and go out at the back.

Since I don't (yet) have my GT to look at, I have no idea how practical this ventilation approach would be.

Bob

[toskeysam]

Originally Posted by uncle_bob

Hi

If you *do*decide to go with one of the Victron 3000 versions:

There is a cover on what is "normally" the top end. In a horizontal mount, that cover probably does not do much good. Right behind it are a couple of fans. I tossed the cover out on mine. It makes it a bit smaller and significantly improves the air flow. That reduces the fan on time / fan noise.

Air comes into the unit from the "bottom" (again as looked at when its wall mounted ....). If I'm guessing right these surfaces would be at the front and back of the passenger seat in the GT. Air would come in at the front of the seat and go out at the back.

Since I don't (yet) have my GT to look at, I have no idea how practical this ventilation approach would be.

Bob

I took the lazy route. My new Magnum 3012 came Tuesday. When the weather permits, I’m going to tackle the installation.

[uncle_bob]

Originally Posted by toskeysam

I took the lazy route. My new Magnum 3012 came Tuesday. When the weather permits, I’m going to tackle the installation.

H

Lazy is something I have a *lot* of first hand experience with

Bob

[toskeysam]

Originally Posted by uncle_bob

H



Lazy is something I have a *lot* of first hand experience with



Bob

Well....crap! I finished swapping out the inverter/charger....no joy.

Same problem. Inverter works fine, but charger will not come out of Standby, and I have no power pass through. The odds on both units failing the exact same way....nahh.

All fuses and breakers are good. Power into the inverter is confirmed good.

I’ve got enough batteries, cabling, fuses, switches and spare MERC50 I can build a test bench for the unit I just pulled. That’s my next step. If it works...at this point I suspect it will. That leads me deeper into the van’s system. It’s going to sit for awhile, until I cool off. Obviously, I’ve missed a possible failure mode and my attitude is not conducive to sleuthing it out just now.

[uncle_bob]

Hi

I don't have any direct experience with the 3010 ( or any other Magnum ). Generic troubleshot would be:

1) Inverter works, that normally means the battery is hooked up properly. Typically this is the most common problem with any charger hookup.

2) No power through the transfer switch can mean one of two things:

a) The relay is not going "thunk" when you switch modes ( = a control problem )

--- OR --

b) Relay goes thunk but no power transfer ( = a wiring problem )

3) Charger just sits there often is a "pick one' as well:

a) It looks at the battery and decides based on it's settings that the battery is fully charged.

b) It sits there waiting for somebody to tell it to go into charge mode.

Victrons have a clunky switch on them for switching modes. They also have a bunch of fun programing you get to do with a dongle and some *really* fun to use software ....uggg ....

So I guess the only useful question I see in all that is: " does the relay go clunk". If it does, then some AC voltage measurements here and there should tell you what is or isn't going on.

Not that I have any first hand experience ... cough ... cough .... but hooking up the transfer switch so the load, shore, and inverter lines aren't .... ummm ... quite in the right places .... errr .... can create a "no pass through" situation .... again, not that I would have *ever* seen such a thing first hand ....

Fun !!!

Bob

[toskeysam]

Originally Posted by uncle_bob

Hi

I don't have any direct experience with the 3010 ( or any other Magnum ). Generic troubleshot would be:

1) Inverter works, that normally means the battery is hooked up properly. Typically this is the most common problem with any charger hookup.

2) No power through the transfer switch can mean one of two things:

a) The relay is not going "thunk" when you switch modes ( = a control problem )

--- OR --

b) Relay goes thunk but no power transfer ( = a wiring problem )

3) Charger just sits there often is a "pick one' as well:

a) It looks at the battery and decides based on it's settings that the battery is fully charged.

b) It sits there waiting for somebody to tell it to go into charge mode.

Victrons have a clunky switch on them for switching modes. They also have a bunch of fun programing you get to do with a dongle and some *really* fun to use software ....uggg ....

So I guess the only useful question I see in all that is: " does the relay go clunk". If it does, then some AC voltage measurements here and there should tell you what is or isn't going on.

Not that I have any first hand experience ... cough ... cough .... but hooking up the transfer switch so the load, shore, and inverter lines aren't .... ummm ... quite in the right places .... errr .... can create a "no pass through" situation .... again, not that I would have *ever* seen such a thing first hand ....

Fun !!!

Bob

The system was working fine the day we got it out of storage. Hooked up to shore power, batteries at 50% charge. System went into bulk charge like always. Ran fine for about 3 minutes and then “poof” it shutdown completely. No final charge state, no nothing except a blinking “standby” light on the charge button and “OFF” in the display.
It’s been working fine for the last 4 years, until this happened. The installation was done by someone we all are familiar with and it was craftsmanship to the “nth” degree. My swap out was easy because of his clean install.

[toskeysam]

Sorry folks.....I’ve been dragging this thread off topic with my issue. I’m outta here.

[uncle_bob]

Originally Posted by toskeysam

Sorry folks.....I’ve been dragging this thread off topic with my issue. I’m outta here.

Hi

Getting dragged around is what happens to pretty much every thread on this forum .....

Bob

[toskeysam]

Problem solved. Found open neutral on Smartplug I installed last Fall. On the plus side, I have a new inverter with new warranty....and I have a good spare 🤣