Factory Solar Wiring Error and Fix - Micro Minnie

[IdahoHunter]

This post is for the new Micro Minnie owners that use a briefcase solar panel in addition to roof mounted panels. I meant to post this many months ago after I upgraded my roof panel controller, installed a controller in the pass-through for the briefcase, added a Smart Shunt, and put marine resettable breakers on both the input and output of the controllers.

Simply put, I found the factory did not run the 10ga battery wire from the roof solar controller (located on the passenger side of the pass-through) directly to the battery. Instead, they ran that 10ga wire over to the driver's side of the pass-through, and they connected it to the 10ga + wire from the SAE socket & the 10ga + wire that runs through the 30A mini-breaker to the battery. So, they have two 10ga wire feeds coming from the two solar panel systems going into one 10ga wire to the battery!

With 200W on the roof and 200W in the briefcase, at full charging with full sun the panels will provide a combined current of right at 30-32A. So, the single 10ga wire to the battery from both controllers would be maxed but not dangerous. However, if someone adds another 200W of panels to their roof, then that single 10ga wire to the battery would be grossly undersized (and so would the thermal breaker mounted on the tongue framing).

This is how the wires look behind the corner panel on the driver's side. The pic is rotated, and the bottom of the picture should actually be on the left side. That left side is where the wires come in from the solar panel socket, which is where I plug in my briefcase panels.



This pic is rotated like the previous one. You can see all the red and white wires are 10ga. The two that go to the battery are labeled "Bat +" and "Bat -". The wires that run to the roof solar panel controller are label "PWR + to RS solar" and PWR - to RS solar". The unlabeled red and black wires are from the SAE socket mounted on the outside of the trailer. The wires that are still crimped go to trailer running lights.



This is just a pic to show how I configured the new controller & breakers on for the roof panels. I did the same thing over on the other side. On a positive note, it's wonderful being able to monitor the two Victron controllers and the Smart Shunt on my phone, and the systems worked wonderfully in deer camp......except for a 3 or 4 day stretch of overcast weather and some snow. Nothing I can do about the weather, and that's why I bring a generator too.

 

[DEWEY-WO]

Hi Mike,

I think for the "as delivered" 2108DS configuration of 1, 190 or 200 watt (depending on what brochure you consult) and potentially another 100-200 watt portable unit, the wiring is more than adequate.

Best case, but unlikely, bright direct sunlight 2 panels generating 400 watts through an MPPT solar charge controller (Victron @ 98% efficiency) at absorbtion charge voltage of 14.4v is going to generate about 27 amps. Not knowing what insulation class of the 10 gauge wire utilized, it could support up to 40 amps, but I doubt Winnebago would plus-spec their wiring, so it's better to assume 30 amps is the limit. 3 amps is a safe buffer. I suspect it would be more than a 3 amp safety factor with the cheap standard factory 30 amp PWM solar controller installed, which specifies 8 gauge wire in the installation manual.

Bright side, you only need to upgrade that 30 amp fuse and a short length of 10 gauge to accommodate your future upgrades.

 

[IdahoHunter]

Hi Mike,

I think for the "as delivered" 2108DS configuration of 1, 190 or 200 watt (depending on what brochure you consult) and potentially another 100-200 watt portable unit, the wiring is more than adequate.

Best case, but unlikely, bright direct sunlight 2 panels generating 400 watts through an MPPT solar charge controller (Victron @ 98% efficiency) at absorbtion charge voltage of 14.4v is going to generate about 27 amps. Not knowing what insulation class of the 10 gauge wire utilized, it could support up to 40 amps, but I doubt Winnebago would plus-spec their wiring, so it's better to assume 30 amps is the limit. 3 amps is a safe buffer. I suspect it would be more than a 3 amp safety factor with the cheap standard factory 30 amp PWM solar controller installed, which specifies 8 gauge wire in the installation manual.

Bright side, you only need to upgrade that 30 amp fuse and a short length of 10 gauge to accommodate your future upgrades.

You are correct about 400w on the roof, and your calculations match mine. However, you forgot to add the current from a 200W briefcase in addition to the 400W on the roof. That was my point and warning to others.

I don't feel I need to upgrade the battery feed on mine above the 10 gauge because I am running 400W total (200W briefcase + 200W roof).

 

[Wmlunt-WO]

My only concern is mounting your controller sideways. The heat fins on the back are mounted horizontal. This hampers the natural convection flow of the heat sink. With the heat sink fins vertical they will pass the air up thru the channels and dissipate the heat correctly.
Bill

 

[eatSleepWoof]

You are correct about 400w on the roof, and your calculations match mine. However, you forgot to add the current from a 200W briefcase in addition to the 400W on the roof. That was my point and warning to others.

I don't feel I need to upgrade the battery feed on mine above the 10 gauge because I am running 400W total (200W briefcase + 200W roof).

Your calculations and concerns rely on having an aftermarket 200W solar panel on the roof, which the trailer did not come with.

The trailer came with a single 190W/200W panel, and capability for the same amount of watts through the external connector. The trailer is adequately equipped for those capabilities. Winnebago went with the cheapest solution for those capabilities, which is no surprise to anyone.

Modifications are done at your own risk, and your own expertise. If that should require tearing apart and re-wiring half the trailer, that's your choice, and no fault of Winnebago.

I blame Winnebago for many, many things, but the wiring they chose in this application is not one of those.

 

[IdahoHunter]

Your calculations and concerns rely on having an aftermarket 200W solar panel on the roof, which the trailer did not come with.

The trailer came with a single 190W/200W panel, and capability for the same amount of watts through the external connector. The trailer is adequately equipped for those capabilities. Winnebago went with the cheapest solution for those capabilities, which is no surprise to anyone.

Modifications are done at your own risk, and your own expertise. If that should require tearing apart and re-wiring half the trailer, that's your choice, and no fault of Winnebago.

I blame Winnebago for many, many things, but the wiring they chose in this application is not one of those.

Attach drawing below from Winnebago shows their wiring plan with the optional aftermarket solar panel. Same wiring, which is the reason for my post.....to warn anyone considering the addition that they need to upgrade some of the wiring.

 

[eatSleepWoof]

Attach drawing below from Winnebago shows their wiring plan with the optional aftermarket solar panel. Same wiring, which is the reason for my post.....to warn anyone considering the addition that they need to upgrade some of the wiring.

If the solar on the side port's output is downstream of the OEM solar controller's output, then that diagram is indeed incorrect.

I have my own copy of these diagrams for my 2022 model, and while they differ from what's in your screenshot, they also show the side port's output going into the solar controller's input, which sure as heck seems incorrect.

 

[IdahoHunter]

If the solar on the side port's output is downstream of the OEM solar controller's output, then that diagram is indeed incorrect.

I have my own copy of these diagrams for my 2022 model, and while they differ from what's in your screenshot, they also show the side port's output going into the solar controller's input, which sure as heck seems incorrect.

Yes, the positive cable from the roof mount solar controller, the positive cable from the side port, and the positive cable to the batteries are all connected together with a wire nut. Not a problem with 200W on the roof and 200W plugged into the side port because that’s a max of 32A, which is close to the max of a 10gauge wire. But if you add any more solar panels to the roof like Winnebago put in the drawing, the 10gauge wire (and the thermal breaker) are not designed to handle the extra current.

 

[eatSleepWoof]

Yes, the positive cable from the roof mount solar controller, the positive cable from the side port, and the positive cable to the batteries are all connected together with a wire nut. Not a problem with 200W on the roof and 200W plugged into the side port because that’s a max of 32A, which is close to the max of a 10gauge wire. But if you add any more solar panels to the roof like Winnebago put in the drawing, the 10gauge wire (and the thermal breaker) are not designed to handle the extra current.

I'm going to be adding extra solar panels this spring/summer. Just picked up a 100V/40a Renogy MPPT controller. My batteries are under the bed, so rather than replacing Winnebago's original wiring, I'll just run new 6ga from the controller to under the bed. Should be a short run, and a simpler job than tearing out + replacing OEM wires.

Hope I can fit another three 200W panels on the roof... somewhere. Worst case, flexible panels on the upper part of the front wall, but I'd like to avoid that if I can.

 

[IdahoHunter]

I'm going to be adding extra solar panels this spring/summer. Just picked up a 100V/40a Renogy MPPT controller. My batteries are under the bed, so rather than replacing Winnebago's original wiring, I'll just run new 6ga from the controller to under the bed. Should be a short run, and a simpler job than tearing out + replacing OEM wires.

Hope I can fit another three 200W panels on the roof... somewhere. Worst case, flexible panels on the upper part of the front wall, but I'd like to avoid that if I can.

Just recommend you put breakers on the input and output of the controller(s). Good protection, plus controllers want to see battery power before they see solar power. Breakers make that easy to do. Both of my controllers feed the battery through the OEM thermal breaker mounted on the A-frame of the trailer. I think it's a 30A. Then I used marine resettable breakers on the input and output of both controllers. Easy work.

Good luck.