Category: RV Upgrades

I’ve been eyeballing this AC for a while. It uses about 1/3 less power than my Dometic Penguin II and it is much quieter. Lots of good reviews.

The main reason I chose Tosot is it uses a lot less power. Also extremely quiet, remote control and Wifi app included, heat pump and (optional) soft start. Its made by Gree, the largest AC manufacturer on earth, and its generally considered good quality. Its sold on both Amazon and directly online by Tosot.

Its almost perfect, but I kept seeing that its only made in a ductless version. But I have a ducted system.

But its definitely possible to modify the AC for ducted install.

Its no trivial feat, as a traditional ductless AC has two pieces that form a sandwich of the roof, so throwing away the bottom part of that sandwich sounded dicey. This is what we are looking at:

So in the lower left you are looking at the rest of the AC which would have to be discarded but it turns out it only has a small control board, sensor, and operation keypad. (I originally ordered white but subsequently cancelled the order and purchased black)

The good news is that there are no thermostat wires, which would almost certainly be incompatible with the Dometic wiring. So it turns out you can make this thing work with ducts (ignoring the fact that the indoor fan was not designed for a higher static pressure, and hopefully won’t be bothered).

I want to do this project DIY because:

• I’ll save a bundle
• Nobody is going to install it as carefully as me and no corners will be cut
• It will be easier to service myself if I am the installer
• It sounds difficult!

So onward! I found a few videos online. As usual I borrowed ideas and techniques from everything I could find or read, and created some of my own.

First step is ordering this thing as it takes a week to arrive.

Meanwhile on to the roof to begin removing my Dometic Penguin II. For context my roof looks like this.

When I originally installed my 600 watts of solar I tried to leave a little room to service the AC on the side – we’ll see if its enough. At least its an easy path to slide the new one on.

It also appears I may have to slide the solar panel directly behind back an inch, but they are mounted on residential solar mounts – just loosen and slide.

A major concern for anybody contemplating this is, how to get the old AC off the roof and the new one on the roof, without a funny YouTube moment?

I’ve seen several methods, ranging from:

• Two guys bench pressing it from a pickup truck.
• A ladder with a harbor freight electric hoist – a makeshift crane
• Two guys and a rope and a ladder

After thinking on it a bit, I decided on this instead:

I happen to have one of these in the garage. They are cheap and sturdy. It has up to a 6 foot reach. So I am thinking if I put the scaffolding in the bed of my pickup truck and drive up to the RV, this will be a a breeze. I’ll set it to about 4 feet or so. So my wife and I will:

• Assemble the scaffolding in the pickup bed (about 2 feet off the ground)
• Place the new AC on the tailgate.
• Lift new AC on to scaffold
• Climb on the scaffold and easily put the AC on the roof (setup a little over 4 feet from scaffold top)

What could go wrong?

A couple other things worth mentioning. Tentatively, I will be removing the control board from the indoor piece, and mounting it (possibly) in the return air vent. That will allow me to use the remote by pointing it there. Its not really ideal, and that leaves me with no physical keypad.

Its not that bad, because there is a remote control and an app.

Also I am going to need a furnace thermostat. The way my RV is wired, the 2 thermostat wires go to the roof and are controlled by the Dometic AC thermostat. Since the new AC doesn’t control the furnace, I will repurpose some of the rooftop wiring. More on that later. Tentatively I’ll be using this for the furnace:

This (I’ll post links for everything below) is an old school 2 wire thermostat that runs on batteries and acts like a switch -exactly what is needed for the furnace. My only concern is that its hysteresis is unknown. (The temperature differential it uses to avoid slow or fast cycling). So I’ll have to give it a try and see if its suitable. For heat I would prefer a nice long cycle and I don’t care of gets a couple degrees colder before coming back on.

Another issue worth mentioning is that there have been lots of complaints that in cool mode the indoor TOSOT fan never stops – even when set on auto. This would be at a minimum annoying, but to make it even worse, many have reported that when the compressor cuts off the humidity in the RV skyrockets.

That would obviously be a deal killer, but its unclear to me why that happens for some but not everybody (sloppy install leaking air on the roof?). Some have installed a “Cielo Breez” Wifi thermostat which solves the problem, but its just too big of a kludge for me since I already have a remote, WiFi, and an app. I don’t need another remote.

The reason the fan runs continuously in AC mode is that the TOSOT has no thermostat except the one in the return air duct. So by leaving the fan on all the time, that thermostat should more closely relfect the real temperature. But I am willing to poke the temperature sensor into the galley.

Mike on the Sprinter Forum already posted a clever solution. He installed a relay which is driven by the outside fan relay – to the inside fan relay. So when the outside fan stops, the inside fan does too. His design only works when fan is set to “auto” as he only applied the relay to the low speed inside fan winding. (The AC is guaranteed to switch to low when the compressor stops).

Here is his instructions: Gree Relay Fan Mod

This is actually perfect – if you want the fan running all the time, just bump the speed up from “Auto”. Otherwise it will act like a normal AC and turn off when the compressor stops (actually shortly after, as the outside timer has a delayed run cycle like most ACs)

Its here! The first to show up was the main AC Box:

It looks fine, and I confirmed no obvious damage. A few hours later, the inner panel arrived, and this is the part that I need to cannibalize:

This is what it looks like out of the box. We are after the control board, which is buried in a box and some foam in the bottom right hand side. First I removed the large steel compartment in the center. That is held together with 4 screws from the outside.

Next I very carefully started to remove the control box itself. I had visions of being extremely careful in case I had to put it all back together, but I didn’t quite succeed. The foam is stuck on and for parts of the Wifi module I had to rip the foam off.

Eventually I was rewarded with the control board. I carefully removed the left and right swing controllers (press the tab down and use a fingernail). I cut off the picture but that leaves the Wifi module,

The first step is to get this mounted in a clear plastic box. After scanning Amazon for quite a while I couldn’t find any that suited me, so I decided to build one thats exactly what I need. It doesn’t have to be pretty. I took a couple pieces of plexiglass and some solvent and made it around 9 x 5 x 1 1/2″. Its mounted with nylon 2.5 x 6mm standoffs and screws.

(Some are missing here – I ran out and ordered more):

This will fit in my return vent. The white probe is a temperature sensor. The control cable mates with the one dangling from the return box in the rooftop with AC. So we are ready to test!

Next I want to bench test the AC. I do not want to haul it up to the roof only to find out its a dud. If I wasn’t so impatient I would have done this step first, before ripping out the control board, so it an easier return!

I just pluuged in the control board. For power I used a heavy 12 awg dishwasher cord for testing and a few Wago’s.

On the floor of my garage – on top of a moving dolly – and – it works! Tried AC and heat pump. All seems fine with this short test. I also downloaded the “GREE+” app and verified I can turn on and off over WiFi. So everything is looking great here!

While running it seemed to use about 8 amps with the compressor running. That is considerably less than my Dometic Penguin II which uses more like 13 amps. It actually seems too low!

I decided to install the fan mod that will prevent the inside fan from running continuously when mode is “cool”. Following Mike’s instructions (above), I took a look at the schematic:

Also take a look at the outdoor fan motor. The schematic there shows the wire colors as white and black for the fan winding. So this will power our relay. If the outdoor fan is not energized, we don’t want the indoor fan running either. It turns out the blue fan wire is the low speed winding on the indoor side. In auto mode, it is guaranteed that once the compressor shuts off the fan will always run at low speed. So we are going to cut the blue wire and connect both sides of that to the NO (normally open) relay contacts.

For the relay (part # below in the parts list) I chose a well respected Taiwanese/US company. You want a mini HVAC style relay thats rated for 120 volts at 20 amps. (Yes that is possibly overkill) But you also want to see the certifications and approvals (UL, etc) and a full spec sheet showing average life cycles and the like.

While the control box is open, lets install the optional soft start that I bought with it. It does not come installed – you have to do that yourself.

There is a video right at the TosotDirect website on installing it. Simple, but DO NOT follow it blindly. Be sure not to tape it down over the screws like the guy in the video did. First time he has to service the AC and open the control box he will have to tear off the soft start. I took the opportunity to put the box screw through the soft start hole so I can still take the box top off if needed in the future. I did end up covering the schematic, so I took a photo of it for reference and put it with the install manual for future reference.

Update: The wire rubbed against the outside shell that way. I don’t want to cover the screw so I plan to remove the screw, pull off the Soft Start, and remount it an inch or so inward. A single screw should hold the control box down fine.

I restarted the AC and tested it. See a pattern here? I want to do everything possible on the ground. I don’t need to be troubleshooting on the roof and potentially have to drag a brand new AC back down the ladder!

Next, what I initially viewed as a scary step, but it’s actually trivial. Drill holes in the new AC! Its scary because I am concerned that I would damage the AC or drill it in a place that wont hit a metal support on the roof. Under my fiberglass roof is 1/4″ wood/luan, about 6″ of styrofoam, and another 1/4″ of wood. Its critical I hit metal on the way down.

I have a back up plan in my head though. If I totally miss metal, its not inconceivable that I plug the hole, and drill another. Or more likely, it occured to me that I could screw a strong piece of aluminum flat bar onto the roof, and use that as an anchor – in other words fasten that to the roof first, and then secure the AC to that. Other solutions like a Z bracket mount would work too, so the more I thought about it – a miss here is not the end of the world.

So I took a look at the front first. Amazingly, it seems TOSOT already anticipated this:

Those 2 cutouts in the front look perfect! I enhanced the right side so you can see the detail in the hole. There is a sort of felt insulator on the bottom here, with a round cutout just waiting for my drill bit. To be extra cautious I drilled a 1/8″ pilot hole followed by a 5/16″ hole. The metal is thin and soft so its quite an easy job. Vacuum thoroughly of course.

My washer dropped right in. Its so tight I couldn’t get it back.

I test fit the original lags and a stainless steel washer that just fits through the square part.

Then the right side hole (looking from the front of the AC, so its really the left).

This was also super easy, and so was the last one:

This one is on a rib. There is not really any place to move it off the rib easily, as it wont fit any further forward. I’ll have to pay attention to this when I mount the AC. Some sort of rubber bushing perhaps under the bottom of the AC to bring it down to the level of the bottom. We’ll see.

But I was reassured as there is really no other place to drill holes – by default this is going to be as good as it gets.

The job was a little easier in my garage with a shop vac and all the tools handy, but this step could have been just done on the roof later too.

Back to my RV. The Dometic Penguin II is not too hard to remove. 4 lag bolts, and LTV Dicor’ed each foot to a rubber mount, which easily seperated with a little persuasion.

The AC feels like it can come loose now with one big pull…

And it did! With the assistance of my wife we used an 18 foot Gorilla folding ladder. And slid the AC down with 2 ropes like a sled. In actuality, friction and bumps on the ladder meant that my wife had to coax it forward from below while I held the ropes steady just in case. (Since I wasn’t that concerned about dropping the Dometic, we decided a ladder was the quickest way down.)

The main reason we did it this way is because I wasn’t ready to do the install yet, so I didn’t feel like dragging my scaffolding to my storage site and assembling it.

Which just leaves a pretty dirty hole up top.

Next, I want to pay attention to the wiring I cut off from the Dometic.

Fortunately there is this nice schematic on the Dometic control board / capacitors box.

I circled in red the part I am interested in. My year has a digital 3 wire thermostat. Its proprietary to Dometic so we can’t use that anymore. Note the the gas furnace wires also terminate up here. So what we want to do is bridge those 2 blue wires back to a pair of the 3 wires that lead back down to the thermostat (red/white, black, orange). I’ll use a multimeter and verify before I hookup to the LuxPro thermostat I mentioned above.

The furnace blue wires act like a switch. Touch them together and the furnace starts.

The easiest thing to do is to identify these 2 wires at the top of this picture:

I selected the red/white and the orange wire. Each of these I capp crimped to a blue wire (doesn’t matter which). The yellow LTV wires are thoughtfully numbered by Triple E, but the numbers were not readable down at the thermostat anyway, but I am certain I have the right pair because of the Dometic schematic above. The remaining 2 wires are just 12 volts and ground so they remain cut off an taped safely.

Finally I connected the new Lux thermostat to the pair of yellow wires in the galley, and the furnace works! Unfortunately in the spring Tampa weather it got kinda uncomfortable testing the furnace so I was brief.

The thermostat is made for 24 volts but is battery operated so I was pretty sure it would still work on 12 volts. Note to self: Be sure to carry spare batteries in the winter. Dead Batteries = No Propane heat.

After cleaning up the roof I am finally ready to look at fastening down the new AC. I am still nervous about drilling holes on the roof for the AC and hitting the metal super structure. Foolishly,I first tried a magnet type metal stud finder. Unfortunately I failed to consider that the metal roof structure is made of aluminum, so that was a waste of time.

Next I was hoping my old Flir (infrared camera) would help:

It wasn’t that helpful. I think I can see some vague outline of horizontal supports, but between the warm afternoon weather and the fact that the LTV roof is sandwiched styrofoam, not really. I could try again on a cool morning (maybe run the furnace a bit) but for now I am just moving on…

I don’t have a forklift, shop, or workbench like you see on videos online. I want to do as much work as possible BEFORE hefting that AC up to the RV.

One other note – my original Dometic Penguin II had a metal junction box for the AC connection using wire nuts. Not the best choice for an RV as wire nuts tend to loosen over the years with motion. I could install a junction box but space is tight.

Some Dometic ACs installed by LTV use a Molex power connectors that look like this (I’ll link all parts used below):

This is a clamshell style connector. The yellow one is for stranded wire (which the Tosot has) while the white one would be for the LTV (which is using solid wire in my case). They are different part numbers. Amusingly, they are listed as hermaphroditic at the Molex site as they are genderless. So any one snaps to any other, they have male and female connectors on each one.

Using Google and AI, they also have a poor reputation in the RV industry. I am going to assume that is user error on the factory install, as Molex is highly regarded. This seems like the cleanest solution to me so I ordered. set. You may already have one side installed, but I didn’t on my 2019.

Why not just use some Wagos and tape over? That would work fine, but Wagos are rated for installation in a junction box. The Molex connector is rated for this kind of “bare” install, so I am more comfortable using them. Also if I have to remove the AC to service, its just a matter of unplugging it.

The video I watched where I got the idea for these connectors – featured a guy putting them together improperly – which is why I am not linking it here. Here are the correct steps:

First you want to cut your wire approximately like this. The 2 halves of the connector come separated, and do not put them together yet. The strain relief is built in, and if you assemble them first, you may not be able to push the heavy yellow jacket through the slot.

Next, lay your masterpiece over the bottom half with the prongs. Now you assemble it. It takes 2 or 3 hands but you can snap the back in first. Then carefully line up the conductors to snap shut. Closing it requires an insane amount of force.

Even with my 20″ Harbor Freight channel locks it took a lot of effort!

Gemini had warned me about this. But if you line it up correctly you can eventually snap lock both sides.

And there it is:

(After I did the other side, I realized it might be easier to just line up the halves and snap the whole thing down at once.)

That strain relief over the yellow sleeve is critical. You want that to hold the wire securely, not flopping in the breeze as you crank down the highway.

The other side goes to the AC. This is a different connector – its made for 12 awg stranded wire.

Again, the strain relief is important. This one is made for round jackets (typically big slideouts in Class A Motorhomes). You don’t want the romex style (rectangular hole)one.

And I made an adapter plate from 1/8″ aluminum.

I will file it a little straigher so its not as jagged. I used a jigsaw to cut the inside and a table saw outside. I also messed up and its slightly offset by about 1/16″. I don’t think that will matter. The larger margins should be around 2 1/16″ and the side margins around 1″. I used the one that came with the TOSOT as a template for the outer dimensions.

Mounted, it looks like this. The inside width (and height) of the LTV duct is 6″. So all we are trying to do is seal off the sides beyond 6″ so we don’t blast cold air into the return air plenum.

Finally! A short drive to install, And yes, it does fit in a mini cooper:

Getting it to the roof was not hard with a little bit of foresight. I have an old cheap 6 foot scaffolding which I assembled in the pickup truck bed. We are going to just stick the front of the AC onto the roof and slide it using the blanket.

This made it an easy 2-step process to lift and slide right onto the roof, where for now we placed it on leveling blocks.

We have a vent pipe on the side and not quite enough room so we used RV leveling blocks as a platform to rest the AC adjacent while we work.

This worked out really great and allowed easy lifting on and off multiple times. Note the area surrounding the hole has been cleaned really thoroughly using 200 proof denatured alcohol and some car wash products.

Now for the exciting part. I have an engineering roof drawing from Triple E (Leisure Travel)and based on that, I am not expecting to hit metal supports. They only have minimal metal supports around the 14″ hole itself, with a couple extras.

This is looking backwards from the front of the RV. So we have the large skylight opening in the front, and then the AC cutout towards the rear. So there is not really a lot of metal in the places where we will be drilling.

Sure enough, I was able to hit paydirt on the two front holes. On both of the rear holes I just drilled into styrofoam.

To make the (2) adapter brackets, I used 2 1/2 to 3″ wide x 1/4″ thick aluminum flat bar. The original lag bolts will hold that to the RV, using new holes drilled close to the old holes. That leaves the problem of how to attach the bolts for the AC?

I settled on stainless “elevator bolts” for the job. These bolts have a very thing head and can stick upward from the adapter plate.

The neck is square so I will probably have to drill a hole and file a bit, and maybe even countersink ever so slightly. But since I am using butyl tape under the plate it should be OK if it still protrudes slightly on the bottom. To make the adapter plates precisely, I first used some left over plexiglass to mark exactly where everything should be and then transferred that to the aluminum plates.

So here is my first attempt:

Note the square slightly countersunk holes for the adapter plates. These were drilled using (rare) square drill bits.

(Just kidding I used a small square file). The square shape prevents the bolt from turning as the nut is tightened.

Each plate will be held down with 2 lag bolts. (One would suffice, but old holes are less reliable and holes are cheap.)

I lag bolted down the plates using new 1 1/2″ 5/16″ Stainless Lag Bolts and washers. Also slobbered self leveling Dicor over the plate for good measure. The elevator bolts don’t sit perfectly flush under the plates, so I also but a lot of butyl tape under the plate as well in an attempt to fasten them down flat (and prevent any water intrusion.)

You can just see it in this picture but I attached the large thick mounting gasket to the RV (vs the AC as the instructions say). I haven’t tried it the other way – seems like you would end up with the same result either way. The other straight one I attached to the AC as per the instruction booklet.

This picture was right after I covered in self leveling Dicor – after a couple days this will look pretty flat and its 90% under the AC anyway. You are looking from the rear at the right – starboard – bolt. Its pretty far back from the 14″ hole which is why I didn’t think there was any chance of hitting the metal support.

The only thing left was to to tighten down the AC evenly. Instead of an impact driver I used a socket set so I could “feel” the resistance and tighten slowly and evenly. You want the gasket slightly compressed all around. I used the original LTV installed rubber “feet” – about 3/4″ think under the front two and starboard side bolts, and a slightly smaller rubber mount under the port side bolt. You want it tight to the roof but too much torque starts to bend the frame and make the cover difficult to put on, which I discovered when I did exactly that.

I almost forgot: the cold air supply duct has some weird rubber material on the van side applied at the factory. I peeled that off and installed some standard AC style 1″ insulation so it sat higher and compressed nicely when I dropped the AC on.

Finally I extended the control wire down to into the RV – there is plenty of room on either side. I decided to use the galley side of my RV to avoid placing it right above my air fryer. I used a piece of junk cat-5 cable to fish it. Then I snap connected the Molex power supply and zip tied it out of the way of the return air but still easily accessible. Its in the picture below under the red arrow.

And here we have it:

Back inside, I connected the control in the vent and flipped the AC breaker:

No magic smoke! It started up and while I was waiting for the compressor to turn on I mounted the plate and air filter.

I extended the thermocouple out through the filter – thinking its better here than in the return duct, and I can live with the appearance. Its still too close to the cold air supply so its possible I’ll put it back inside the return air duct. I originally thought it would be too warm in there. However dangling out like this, its possible the AC ends up with shorter cycles than I’d like. I think RV ACs tend to cycle on the short side anyway in the sun as they quickly heat up when the AC turns off.

(I am also thinking that I could drill a small hole in the ceiling and extend it down on the other side of the “Blink” security camera where it would be out of sight more and no longer directly receive cold air.)

I did note that Mike’s relay mod works perfectly as on “auto” when the compressor turns off the inside fan turns off shortly after like a “normal” AC.

The remote works fine by pointing at the vent. It also comes with a very nice Wifi app that lets you monitor and control the AC, and I will probably end up using that more often than the remote.

The AC does blow extremely cold air so that definitely does not disappoint!

I try to learn from each project, and if I was doing this today I would have made a template first of the TOSOT showing return, cold air, 14″ opening, and newly drilled holes. That would have allowed me to play with the template on the roof a bit. I started to do that but cracked the plexiglass and abandoned the idea. That center duct adapter I made – I could have offset that to slide the AC and inch or more left or right – and possibly hit a support metal on at least one of the rear holes.

For parts, I used the 120 volt Molex connectors:

Side	Wire Type	Molex Part Number	Boot Style
RV / Supply Side	12 AWG Solid	19045-1000	Flat Romex
AC Unit Side	12 AWG Stranded	19403-1010	Flat / Soft Sleeve

You will probably not find these on Amazon – I purchased from Digikey or Mouser.

Square neck elevator bolts, Stainless steel 18-8, 5/16″-18 x 2″
AC Fan Relay

Everything else I mostly purchased on Amazon:

<Links are Paid>

You can find 5 YouTube videos on replacing your chassis battery, but they all leave out some super important details. I like to go all the way down the rabbit hole with everything, so I’ll share my experience.

First, only do this if you have the older chassis like mine!

Newer, like most German vehicles, have “adaptive charging” which gradually raises the voltage as the AGM battery ages. I found this out the hard way when I replaced my wife’s 2017 Mini Cooper battery.

Worked great, and then fried in 12 months. Thats because you have to go to the dealer and have them recalibrate the battery computer setting. Otherwise the higher voltage quickly ruins your new battery.

Anyway the 2018 does NOT have this feature. So battery replacement is a simple drop in experience.

All of the YouTube videos I watched used an aftermarket battery. That’s fine, an Interstate equivalent can be found at Costco for $180. But the OEM battery is more than just OK – mine is going on 8 years old and still going strong. I am just replacing it proactively. The OEM battery is a piece of art.

I couldn’t find it online – only a Bosch S6588B which appears to be the same battery – but its a whopping $400 plus shipping, and not available locally. Then I called the local Mercedes parts department – which I assumed would be similar – and – surprise – a genuine OEM battery was only $240.

Is this battery really any better than the Interstate at Costco? Only time will tell. The warranty is worse – only 2 years – but when I am 100 miles from the nearest auto garage in the middle of nowhere, I’d like to know I bought the very best, and I think this battery is, if its anything like the one that came installed in 2018.

The install is actually quite easy. The battery is located under the drivers feet. You start with this L-Shaped trim with 4 screws:

Remove it. You will use a T-25 screw bit. Next, fold back the carpet and remove the plastic underlay. Finally there is a black metal panel on the floor with 4 screws. Remove that.

This will expose the battery: There is a red safety cover on the positive, which I removed:

It looks complex, but you will only be removing the two posts just like any car battery. You wont be disassembling anything.

Before going any further, remove the ground bolt from under the driver pedal for safety. As an additional safety measure I flipped the breaker on my DC-DC charger so the battery is not getting any reverse feed, To be extra safe unplug the RV from AC.

On the left side note there is a vent tube, Pop that off. Then, using a 10 mm socket with an extension, there are two bolts holding down the battery on either side of the tube. Using a flashlight here helps. Remove the plastic hold down assembly.

Then remove the negative battery lug using the same 10 mm socket. I always treat everything as hot, so I placed the negative lug in the plastic red container to avoid letting it touch metal and become grounded.

Finally, remove the positive lug. Its connected to a plastic power distribution box, but there is enough slack to pull the whole box out. After I did that, I tied it back so it would stay safely out f my way and also, avoid any metal conductors. (Again, pretend its hot. Maybe you forgot something).

As you can see this leaves easy access in case you don’t have a helper. From here you can open the handles on the top and remove the battery, leaving an empty compartment.

Before replacing the new battery, be certain to perform a crucial step! Remove the right side (positive) vent plug from the old battery, and place it on the new one. This is important because otherwise you could potentially be venting the battery (explosive and poisonous) gasses into the passenger compartment. You only want one vent on the left side, which is vented outside through the tube.

Then drop in your new battery. For safety connect the positive side first. Be sure to not over-tighten. I believe about 50–70 in-lbs (approximately 4.2 to 5.8 ft-lbs or 5.6–7.9 Nm) is correct, which is not a lot.

The negative next, and then reinstall the positive side cover plate:

That is pretty much it! Reinstall the covers and enjoy the savings. Mercedes charges $600 in my area.

Most of the DC gear in my RV is Victron – the BMS 712, 50 amp solar MPPT controller, and an old Venus to connect to Victron VRM (remote Internet monitoring).

I always wanted a Victron Inverter/Charger but I don’t have the space, location, or weight capacity to mount one, so I settled on a Xantrex XC 3000 Pro.

The Xantrex has worked very well but does not have any sort of remote monitoring.

Except – over time they (Xantrex) have updated it to have CAN bus / RV-C support so in theory it can talk to Victron, and even display live status info and controls on a Victron app or touch screen. The only thing missing is a (big) program to do this trick. I figured I would write one.

Right around the time I started looking to see if I could do that, I discovered that somebody already had!

I stumbled onto this: https://github.com/ScottS45/Xantrex-Rvc-VenusOS

So, what I found was not only was this possible, but Scott has a (mostly) working version already running. I got in touch with Scott and volunteered to do some testing. I found his program incredibly complete and useful, but a some sections he had not 100% finished. I recommended some patches after testing and Scott came through with some quick improvements, mainly on displaying charging information. Thanks Scott!

At the link above, Scott gives instructions on connecting the CAN bus from the Xantrex to a USB converter and to a Raspberry Pi, but I just want to connect it directly to my Cerbo GX. (I just bought a new Cerbo GX to replace the old Venus)

I started with this article by Victron to gain root access to a Cerbo type device. Venus Root Instructions

Then I figured out I just needed to connect 3 wires from an RJ45 to the 20 pin Molex connector that is standard on the Xantrex XC Pro models.

Lets start with the Xantrex Molex Connector.

So, we just need to connect 3 wires to the Xantrex:

• 12. CAN ground
• 11. CAN high
• 1. CAN Low

Over on the Cerbo, the CAN ports are RJ45 jacks. So I just took a random network cable laying around, and cut off one end. As far as figuring out how to pin it, lets look at the Victron documentation:

This shows us that we will be using pins 3,8, and 7. Note that the colors listed above were right in my case, but don’t depend on that always being true as there are at least 2 network wiring standards that I know of. So I looked carefully at the RJ45 to verify I had pins 3,8, and 7.

I hate trying to crimp Molex pins these days – they are too tiny for me to see easily, so I just keep a box of Molex prewired pins on hand with a bunch of random sized Molex connectors. So I just grabbed 3 wires, pushed them into a 20 pin connector, snipped off the other end, and temporarily crimped them to the appropriate RJ45 wire. (Later, for the permanent RV run, I will solder up a nicer splice.)

Next, I updated my Xantrex PRO completely. By that I mean all three updates – Main, Bluetooth remote, and the “Communication Interface”. Unless they are all running the latest firmware you will not have good results. These are all available from Xantrex. As an aside follow the instructions very carefully as its quite possible to brick your Xantrex if you really mangle this, like turning it off while its updating.

And finally make sure your Cerbo, Venus, or Raspberry Pi is likewise running the very latest version.

Then I:

• Created /data/xantrex-service
• Placed Scott’s program there
• Downloaded the Venus library per his instructions
• Started his program

And, amazingly it works! I now have the Xantrex reporting status (somewhat) accurately on my Cerbo.

As an aside, I always wanted the Cerbo remote display but find it impractical as it requires an HDMI cable and is expensive. Then I stumbled on to this beauty:

https://community.victronenergy.com/t/new-use-an-android-tablet-as-dedicated-gx-wi-fi-display-beta/8575

These instructions detail the procedure to turn a cheap Android tablet into a GX display, over local Wifi, so no wiring!

You might be wondering why bother to do this, as any device can be a GX display. But this puts a tablet in “Kiosk” mode and hardwires it as a display, so its always running and you won’t have to login periodically.

Now, back to my RV a while later, I mounted my new Cerbo (upside down, as that was all I had room for). Fitting as my inverter is likewise upside down.

I made a custom RJ45 cable just because I had a roll of CAT6 and the tools laying around, and except for a few zip ties and some cleaning up of the wiring above, this is basically it. Plugged into the Xantrex and everything works as expected.

For the first time I can see the Inverter mode, and the AC load. Clicking on the Inverter gives some additional information but not a lot yet.

In the future I hope to continue tinkering with the program to allow me to remotely control the charge rate and float voltage, settings I change often, but for now this is a great little remote upgrade that lets me spy on the Inverter from anywhere in the world.

To permanently install Scott’s program and automatically restart, I created start.sh in /data/xantrex-monitor:

#!/bin/bash
cd /data/xantrex-monitor
nohup python3 xantrex-service.py –can vecan1 &

(Adjust can port for your installation) Make the script executable and link to auto-restart:

chmod +x start.sh
ln -s /data/xantrex-monitor start.sh /data/rc.local

After that whenever the Cerbo reboots the Xantrex service starts automatically.

Update: May 11 2026

I reported a few small issues to Scott and worked with him on some minor improvements. One issue I did have us that the DC charge and load were overstated – perhaps doubled. I made the following patch to stop reporting the DC charge: (I already get that from the Victron BMV)

The remaining issue was that when inverting, the DC load was aproximately doubled. My trivial solution was, on my Cerbo, just turn off display of DC load. (You still have the DC load under the battery so nothing is missing). This is a setting on the Cerbo UI. So then you end uo with this:

Perfect!

(If you are wondering why in the beginning of this post I was using 14.5 amps I had the AC running. In the last screenshot I’m running on battery and using only 9.7 amps AC. Why? I recently installed a TOSOT 16000 RV AC!

Here are a few parts I used for this installation including the Cerbo itself:

Links are Paid. Click on a link to see product at Amazon.

Well into my trip to Canada I encountered the dreaded “08” and “07” errors on my Xantrex Inverter. This indicates at least one of the fans has failed. In my case, and probably most cases, the fan hasn’t actually failed – the tachometer signal the fan sends back to the Inverter to prove its running – stopped working.

This is a pretty catastrophic error. The Xantrex goes into “bypass mode” (so you can still use generator or shore power) but you loose the inverter and battery charger.

Fortunately, I have an onboard Victron 25 amp battery charger that’s wired permanently and I’ve never actually used in 4 years. So I just had to turn on its breaker and at least I had a small shore power charger again.

Since my inverter is quite difficult to remove (have to pull both batteries first) and since I was in Canada at the end of my trip anyway, we just headed home.

Reminded me of the old days – starting the generator at a rest stop to make coffee!

Once home, I pulled the Xantrex out and started examining it. the case is secured with many small screws. The bigger one has a round sticker over it, and likewise the date code on the other side has a small screw under it. (Obviously you are voiding your warranty)

From online reports, Xantrex tells customers to throw the Inverter in the trash when the fan fails. Hopefully this is an easy fix.

Once you get all the screws off, gently open the top and rest behind the Xantrex.

The circuits are all protected by the paper guard you see above. I had already cut a few zip ties and peeled back the top part to expose the fans so I could get a part number. I subsequently decided to make two scissors cuts so I could remove the guard. I didn’t see any need to remove the cover or disconnect all the wires that are not really in the way.

The fans are easily removed. These are the culprits:

A Google search shows these are really rare fans. I found them on the Chinese manufacturer website and also a Hungarian website. Although one or both had failed, they have been spinning for 4 years outside so I really can’t complain. But I didn’t want to wait weeks for a replacement to ship (not to mention the [shudder] tariff these days) – so I started looking for a replacement.

These are 92mm X 25mm fans so not that hard to find. I used chatGPT to search for replacements and here is one of these sessions:

So in the chart above the first entry is the Xantrex OEM fan, the second is a common fan available immediately on Amazon, and the last (and the ones I chose) a higher quality industrial fan not usually sold on consumer sites like Amazon but available on Mouser.

I chose the Delta because its a solid fan and its airflow is significantly higher than the OEM fan (which is already a beast). The Arctic fan in the middle of the chart (recommened by an excellent video I found online) was available on Amazon Prime, but both the Airflow and current were significantly lower. This causes me to suspect I would experience issues in extreme conditions which I encounter sometimes in the summer heat.

The Delta fans are real monsters for this size, and louder. But the fans only run on full speed when needed, and are barely audible in the coach, so I can live with that.

I overnighted them (ouch) from Mouser (link below) and they showed up bulk wrapped with no connector. Which is great, as the Xantrex uses a non-standard 3 wire plug anyway – which is skinnier than standard PC fan plugs. So I had to cut the connector off the Xantrex fans and solder 3 wires on each to the new fans. The 4th (PWM lead) is not used.

Note that Delta uses Blue for the tachometer, so the wiring is red to red, black to black, and yellow to blue.

I used “Western Union” splices and solder, covered with heat shrink tubing and zip tied for safety. This picture shows the new fans installed.

The grills were rusted, so I also installed new fan grills. This is the exterior view:

To test it, I just connected a standard AC cord:

I plugged it in and it worked great! These turbo fans really do push some air. You get an error initially as there is no battery present but then eventually it settles down, spins down the fans, and its ready for reinstall.

So this failure has a happy ending. For a small amount of money I got enhanced cooling and reliability, and we are off and running again.

Here are some useful parts. The fans are available at Mouser If Mouser is out, the Amazon Link below may have stock:

<Links are Paid>

The Epoch 300 is so popular that they are literally everywhere. And for good reason. It’s a high quality budget battery made by Roypow, which is a Chinese conglomerate with a good reputation. It normally sells for $995 but with the Black Friday sale after thanksgiving I purchased mine for just $799 each. The price, quality reputation plus their diminutive size, made them a no-brainer for me. I got them ahead of any tariffs coming which may affect pricing in the future. $1600 for 600 amp hours is incredibly cheap compared to just a few years ago when the equivalent Battleborns would have come to $6000.

For starters my Discover Blue 200’s are going to be a tough act to follow. These batteries have a bunch of killer features almost never seen in lithium batteries. A user replaceable BMS, built in terminal fuses, and screw down simplicity to begin with. The Epoch has none of these, but packs 50% more spinning electrons in (roughly) the same package size, so I am willing to forego some convenience to raise my battery farm from 400 AH to 600 AH.

I always start with a full capacity test to make sure the batteries are working properly. So using my old Magnum inverter, a small Vicron charger, and a cheap battery shunt off Amazon, I fully discharged each battery to around 4% to be sure all is good. I’m too lazy to go through all the bother of installing these only to discover one was damaged internally by being dropped by Fedex. For testing I used a hair dryer set on low, which is around 750 watts.

As expected they worked great.

For background info, I use some clever Marinco products to simplify and improve installation. The genius of the BEP line is that these products all connect together using heavy duty busbars. (Links to products below).

On my desk, it looks like this:

Originally I designed this for 3 batteries but for now I am using only 2. If you follow the battery bus bar, it leads to the class “T” 350 A fuse. That connects to the switch, so you can easily turn off 100% of the rig for safe long term storage with no parasitic drains.

The first 2 switch positions are both “ON” but the “Parallel” click is where the inverter is connected. You can’t see it in the picture but the inverter is connected where the switch says “Parallel” with huge 4/0 wire. So there is another safety/convenience feature here that unless you click down to “Parallel” the Inverter is 100% disconnected from 12 volts, which is useful for storage or maintenance.

So in one convenient package here we have the ability to switch off batteries and/or inverter and all without any wires.

Mounted, it looks like this:

The “bus bar” method is the safest and best way to interconnect batteries. Each battery will have a terminal mounted Blue Seas 250 A fuse and use 2/0 wire.

The connections to the Marinco assembly above use 4/0 wire as they carry the aggregate current. The class “T” fuse is conservatively rated at 350 amps which is less than the 2 batteries can continuously produce but much more than I could ever be wanting to use at once. It also keeps it around the 300 amp continuous rating of the factory installed Bussman Mega fuse holder.

So on to the batteries themselves. I added Blue Seas 250 amps terminal style battery fuses so each battery is individually fused. This protects a high load or dead short in one battery from ruining the other one hopefully. (I never trust high current overload shutdown after the Lithionics debacle where they were found to melt internally under high load.) While the Lithionics failures were particularly egregious, Will Prowse has pointed out this feature is not always reliable on other batteries as well due to software errors or just poor design.

I bought a 4 foot long piece of aluminum 1″ angle stock from Home Depot, and cut sections to use as battery mounts. It is extremely important that these batteries be mounted permanently and rigidly to prevent vibration damage or worse (like a fire from loose connections). Also a 1″ flat aluminum bar to hold down the top, with some Amazon “J Hooks” holding it down.

If you look under the hood at a modern car the battery is typically housed in a metal box and held down with bolts. If you look at a typical aftermarket house battery mounted in an RV by the owner, not so much. I’ve seen everything from nothing to packing foam blocks to string being used, none which works as well as metal.

The greatest challenge by far is mounting these in a small enclosure! I sure wish battery makers would take a hint and add screw mounts like my Discover batteries. But lacking that, I bought some Home Depot Aluminum 1″ angle stock. Its hard to see in the other pics so I zoomed in:

So basically I installed one in the rear and both sides and although its quite rigid now with the top bar I will put a little foam spacer between the batteries and the front metal just in case the top bar should rattle loose someday.

This is the final picture powered up and running. The mount is tough enough to take the jostling that we sometimes encounter on back roads out west leading to remote camping spots.

Note that my inverter was moved to the left side (long story) so I installed the batteries in this orientation. This way the bms (which is now on the right side of the battery in picture above) is right next to an air vent for cooling and away from the inverter. For a standard Unity with the inverter on the right side the batteries would usually be flipped around with the Epoch logo showing on the front.

When connecting, I first checked to make sure both batteries were very close in voltage, with less than .05 volts difference. Then I connected the positives first (both batteries) and finally the negatives after making sure my Marinco master switch is off. There is just enough room inside to (barely) connect the negatives, and fire up the app and with satisfaction watch the battery that had a tiny more charge drain off to its neighbor.

And lastly turn the Marinco switch to on. Wait a few seconds. This is to allow the battery to fully boot and stabilize. (Not really needed in this scenario, because the Epoch BMS seems to be always on and my Xantrex inverter does not have a huge inrush current like the Victron does, but good practice anyway). Then to “Parallel” to connect the inverter.

The Epoch bluetooth app is pretty good and includes the ability to turn the MOSFET (internal transistor switches) on and off – both charge and discharge. Since the battery uses an off the shelf “JIABAIDA BMS model jbd-sp04s060” there are probably a dozen apps you can use. I’ve tried a few. Some allow you to save the (dozens) of bms settings.

Which leads to the only thing I hate about the battery. There is no provision for a Bluetooth password. Because of that, a camping neighbor could, through mistake or willfully, turn your batteries off, or even worse, change an internal bms setting and fry them. (The Epoch app does not allow this, so most campers woudn’t have that ability).

This is all extremely unlikely obviously, but still, in the world we live in today, it would have been better if Epoch had setup the Bluetooth dongle to enable a password, or only allow pairing when a switch was pressed or something.

The Epoch BMS is very standard. I setup all my chargers for a 14.2 volts absorption, a 13.5 volts float, and a 30 minute fixed absorption time with zero tail current. I let the Xantrex top them off, and everything looks to be working great so far.

March 2025 Update:

Batteries working as expected. I happened to visit their website one day and now they sell these gems: Would have saved me an hour or two’s work buying, cutting, and installing sheet metal brackets, so this would be the way I would go if installing now!

October 2025 Update

After my Xantrex failed on the road I had to remove the batteries to service it. The battery mounted terminal fuses became a real pain! I don’t have much clearance, and they were a friction point getting everything torqued down easily and safely. Thanks to a conversation with another LTVer, I became aware that they also make a dual terminal fuse. The beauty of this is I could just hang it off the Class T fuse, eliminate a bus bar, and make it much easier to slide batteries in an out.

So in the picture above you can see the fuse bar hangs directly on the Class T fuse, and gives each battery a 250 amp fuse – but moved the fuses off the battery for simplification. Before I mounted the red safety cap it looked like this:

Some of the stuff I used, besides the batteries themselves:

(Links are paid)

MRBF Dual Fuse Bar