Help With Solar Install

[InTentsKristen]

Hello everyone! I am looking for a little help from someone who is hopefully more knowledgable than I am on electronics and wiring.

I have a 2019 Jeep JL Rubicon with a hardshell rooftop tent. On top of the tent is a Merlin Solar panel that has wiring running down into the back of the Jeep. Inside I have a Dometic PLB-40 battery that plugs into the panel and then runs my Dometic CFX-35 fridge.

Issue: The PLB-40 is somewhat finicky, and if the solar panel isn't in direct bright sunlight, it complains with a continuous audible beeping and error to indicate it cannot charge. IE: the input power isn't sufficient to charge. This means anytime I'm in shade, even if it's for a few moments driving down the road, the battery starts to error and beep. Driving back into sunlight does not reset the battery -- I have to unplug the solar input and plug it back in to reset the error.

Obviously this isn't very convenient as it means I can only charge the battery in direct high sunlight, and if a cloud or rainstorm comes up while I'm driving, I have to pull over and unplug the solar panel or be annoyed with constant beeping.

I'd like to install one of two solutions:
- #1) A device that only sends power to the battery when the watts / amps >= a set value. IE: it cuts off charge to the battery when the panel output drops, thereby preventing the error. OR:
- #2) Using one of the Aux switches in the Jeep, wire up some sort of switch that "turns the solar panel on /off". Effectively a switch that I can press when I'm in sunlight to charge, but I can press to quickly disable charging if the input power drops.

Option #2 would be my preference, especially if I can wire it to the factory Aux switches in the Jeep. Anyone know if something like this is possible? What sort of part am I looking for do this? When I google for cutoff switches I tend to get results designed for more residential applications that are too large. I'm guessing there's a name for the type of device I need, but I don't know what it is. Any help is much appreciated.

 

[Flipper]

Why don’t you use the solar when stationary and use the vehicle to charge the battery when on the move? ACR by BlueSeas. Simple set up. Would be a lot more efficient and faster.

 

[InTentsKristen]

Why don’t you use the solar when stationary and use the vehicle to charge the battery when on the move? ACR by BlueSeas. Simple set up. Would be a lot more efficient and faster.

Unfortunately that still wouldn't "out smart" the battery. If I am stationary in shade, the relay would switch to the solar, which would have insufficient input, and we'd start the beeping cycle....

 

[Flipper]

Unfortunately that still wouldn't "out smart" the battery. If I am stationary in shade, the relay would switch to the solar, which would have insufficient input, and we'd start the beeping cycle....

I get it now, #2 option, Thats the ticket.

 

[InTentsKristen]

Unfortunately that still wouldn't "out smart" the battery. If I am stationary in shade, the relay would switch to the solar, which would have insufficient input, and we'd start the beeping cycle....

I get it now, #2 option, Thats the ticket.

Yeah, I just need help figuring out what to buy to make #2 a reality?

 

[Flipper]

Yeah, I just need help figuring out what to buy to make #2 a reality?

You could do it with a 12v relay then you wouldn’t have to deal with switches and a stock circuit in the Jeep with a high current draw. You also wouldn’t have to run heavy gauge wire and buy expensive specialty switches.

 

[Kerner]

We put in a pair of double pole single throw switches into the control panel of our teardrop. The SAE jacks for the panels run to the switches, the switches run to the charge controllers. When we don't want the solar panels active we just flip the switch off. We primarily did it be able to disconnect the solar when the battery isn't connected or we're on shore power.

 

[InTentsKristen]

We put in a pair of double pole single throw switches into the control panel of our teardrop. The SAE jacks for the panels run to the switches, the switches run to the charge controllers. When we don't want the solar panels active we just flip the switch off. We primarily did it be able to disconnect the solar when the battery isn't connected or we're on shore power.

View attachment 200450

The pair being needed to shut off the positive and negative wires?

 

[Kerner]

We put in a pair of double pole single throw switches into the control panel of our teardrop. The SAE jacks for the panels run to the switches, the switches run to the charge controllers. When we don't want the solar panels active we just flip the switch off. We primarily did it be able to disconnect the solar when the battery isn't connected or we're on shore power.

View attachment 200450

The pair being needed to shut off the positive and negative wires?

The pair is because we have a double solar controller setup on the trailer. The double pole switch disconnects both leads.

 

[socal66]

I have a JLUR and Dometic CFX-35 fridge as well and run solar. I am using a Bluetti battery which like your Dometic battery has just one DC input so it is either solar or vehicle power but not both. What I needed to add was a MPPT smart dc-dc charger to control the power input from both. The MPPT will not only allow for managing both power sources but will also regulate the input voltage. Something like this may work to ensure that your battery will only get current within a specified voltage range.

Another solution would be to just charge the battery from the car power and have the solar charge the car battery directly. The JL fuses can be setup to cut power from the rear 12V plug when the car is not running to save your battery. Assuming your Dometic battery is sufficient when you are in camp and can get recharged back while on the road would make this work. Alternatively you can just feed your second battery from the main Jeep battery all the time which in turn would be solar charging while stopped.

I don’t think you would want to do #2. The aux switches are conveniently wired to the main battery and you would need to sever that connection including the grounding along with routing your wiring to the dash to make that all work. Best to just have a separate “kill” switch if you are going to go that route.

 

[Prerunner1982]

That's sounds annoying as hell. I would understand the audible alarm if the battery was not getting power from the solar panels and the battery charge dropped below a certain critical level but as soon as there is shade seems a bit excessive.
Option #2 would probably get you by but I think the better option is to get a charge controller and a different battery that won't gripe at you when there's a little shade and maybe think about adding an extra panel with a longer cord on it so that you can move it around while set up at camp, IF you stay at camp for more than a day or two.

 

[leeloo]

Even in shade the solar should supply enough voltage. So a 100W solar panel should put out idealy maybe 7 amps even 9 amps ( never seen tough, maybe at the Ecuator :) ) in a good day, right ? In shade maybe as little as 2 amps, but should deliver something. That means, in theory the cables from the solar panel to your controller/battery what ever - can be pretty thin . Wrong, what ever the reason with thin cables that in theory should work, you have a huge voltage drop. This is how you recognize good quality solar kits. My foldable solar panel cables are almost as thick as the 110 Amp cables I use from the alternator to the DC, they came with the kit like this. So look in to that.
What I would do do diagnose the issue :
I would measure the the voltage exiting the panel, the voltage at the entrance in the PB Dometic thinghie, in shade conditions. If there is no significant drop, cables are ok and that dometic PB40 has an problem. Looks like a bad design/bad engineering anyway , not only because of the beeping but the fact that it needs a reset every time, that is just plain bad
Man that thing is expensive for what it is...
Whoever is looking in to something like that should get a victron box, much better quality and impeccable reputation.

 

[Kerner]

Which brand is the monitor "battery capacity tester"? That looks very nice!

trippin

It's one I bought of Aliexpress - basically the same as the Renogy monitor.