Help Me With My Solar Setup

[Gmr213]

I'd like some help with setting up my solar set up. Recently I purchased a used rig that has the following:

Genesis dual battery system with odyssey 34-PCT1500T batteries
ARB 50 quart fridge with jacket wired to the batteries
Various camping LEDs wired to the batteries
USB chargers in the roof tent

I was also given two 100 watt solar panels having talked to the seller after the transaction was complete. Best I can tell these have MC4 connectors on them. The previous owner hard mounted these to a roof rack and used them to power a goal zero yeti, I do not know which size.

Instead of purchasing a goal zero yeti, I would like to streamline the setup and connect the solar panel(s) to a solar charge controller that connects to the dual battery system.

I anticipate my electrical needs as the following:
-Continuously run the ARB fridge. Sometimes I am in hot climates (100F), and sometimes I camp a few days at a time without turning on my vehicle
-Charge two iphones overnight
-Use LEDs on the exterior of the vehicle and inside the tent
-The occasional laptop or ipad charge to watch a movie (whatever it takes to get the lady on a trip...)

In my two weeks of ownership I have managed to run 3,500 miles of overlanding. During this time I continuously ran the fridge off the batteries and nothing else as I was unsure how much I could push my new setup and did not run into any problems. The lowest my batteries got to was maybe 12.2v. The rig has been off for about 5 hours and the batteries are at 12.7v.

All of that said, here are the questions I am currently trying to answer:
-Can anyone point me to a specific MPPT that would meet my needs?
-How do I determine the correct specifications on an MPPT? (In terms of their rated amperage and voltage)
-How can I verify I can plug my MC4 connector(s) off my solar panel(s) into the MPPT?
-How do I connect the MPPT to my battery system?
-With the genesis, is there any specific recommendation to connect to one battery or the other?
-Am I ok to run one 100 watt panel, or would two 100 watt panels better suit my needs? (or maybe this answer is no panels needed...)
-Any other advice or resources I should read?

I am new to solar so I appreciate any advice. Thanks!

 

[luthj]

Where do you live, and what seasons do you plan on running the fridge? Solar charging varies dramatically with the seasons. Are the panels flat mounted to the roof or? Do you drive the rig regularly, or do you plan on parking it for extended periods?

What is the daily power consumption of the fridge?

The batteries you have suggest a absorb voltage of 14.7V. If you are not getting near that with your current charging source, you will probably see reduced lifespan.

How is this dual battery system wired? Are they separate when the engine is off? Does it use a combiner relay, or DC-DC charger?

 

[Gmr213]

I live in Denver Colorado and I also daily this rig right now, so I guess the season question is pretty important. I’m not sure I intend to run the fridge during the winter at this point. Maybe for the odd trip or two.

The fridge manual has a rating of 7A at 12V

With respect to the panels I have two hard 100 watt panels. I have mounting hardware to place one or both on the roof.

I am not 100% sure how to tell how my batteries are wired, so I will be researching that over the next few days.

 

[dwh]

You won't be able to connect MC4 to the charge controller. The charge controller will have screw terminals.

The way it's done is to buy an MC4 extension - male on one end, female on the other - and cut it in half to get two "MC4 to bare wire / screw terminal" adapters.

https://www.amazon.com/Renogy-10AWG...sion+cable&dpPl=1&dpID=41pcYsH3ajL&ref=plSrch

 

[DLTooley]

The fridge is your big draw. The 7 amp/12v number (84 watts) is the maximum running temperature. How often it runs will depend on the internal setting and external temperature. 200 watts of panels won't produce a whole lot more than that in real world conditions, but you should be good. You do want to monitor actual use and solar production., 100 degrees and a deep freeze might be a full time run.

The Victron MPPT 75/15 monitors both charge and load - it's a bit spendy at $120, but I consider that capability a necessity for my fridge. I run my 3-4 amp as a deep freeze only during daylight hours, which puts much less of a load on my batteries. It's a bit under-powered, but marginally works. I don't know about your specific batteries. You can make your own cables, my multiple die set crimper is being delivered today.

 

[llamalander]

I'll second the suggestion of the Victron MPPT charge controller. The Bluetooth app it comes with is almost as much meter as you need, easily programmable to work with specific battery types and useful to see when you are getting power and how much. It will record your input and usage for 30 days making it very useful for determining what you actually need to run what you have.
If you have room for both panels, this controller lets you wire them in series, you will reach charging voltage for the batteries with lower light levels and have a longer charging period over the day.

When power comes out of your charge controller, run it to your Aux battery bus, which is hopefully a fuse block. Feed it through a fuse and mark it as a secondary power supply. Whenever it can produce a voltage above the battery, it will charge it or help run whatever load is drawing the battery down. Your vehicle should take care of its own charging needs, so run your extra loads off of the Aux battery and use the solar to finish charging that battery when the alternator has done what it can.

Vehicle electrical can be fairly time consuming and much less fun when you have to redo it. Having all your components on hand, knowing where you can put them and get wires between and making a detailed plan will be a huge help. You can get a lot of good feedback and useful tips if you post up a plan here before you get out your wire-strippers or start making holes in your firewall..

For random tips, I think it is worth running a ground back to your Aux battery fuse panel for every circuit. Avoiding the urge to just ground to the frame can save you many headaches if you have to start troubleshooting.
For solar, it is important to run the negative line only to the charge controller, and worth fusing along with the positive before you get there. When you need to disconnect the solar, pull both fuses.
In general, if you can manage the voltage drop with larger wires, think about avoiding relays for smaller, switched, loads and keep things as simple as you can.

Check out PKYS.com for lots of info on DC systems, sizing charge controllers and really good prices-
https://shop.pkys.com/Victron-Energ...-Charge-Controller-with-Bluetooth_p_2779.html

BlueSea is another great resource, their wire & fuse sizing charts are detailed and clear. It's worth taking the time to learn how (& why) DC systems are properly fused, poor wiring is a quick way to light things on fire. If you still want to wire your truck after that, just do a quick read of all of DWH's posts and you will probably have all your bases covered...

 

[Gmr213]

Thank you for the incredibly detailed response. I’ve got some homework to do reading up on those resources you’ve posted. It might take me some time to get to a level of understanding where I’m comfortable getting parts but I’ll check back here for future questions

 

[FJR Colorado]

I myself prefer a completely discrete solar power system with its own deep cycle battery. But to each his own...

You can search my 20006 1st Gen Tundra build if interested.

I too live in Colorado. Plenty of sun with a 100W panel to run your fridge 24/7/365. Yes, do run it all winter.

One year I even rigged up a heater that would kick-in below freezing to save things from turning to ice.

 

[Gmr213]

That’s great to hear with respect to running a 100 watt year round. I also very much enjoyed your build thread. If only I had an off the grid retreat in the mountains

When it comes to running an isolated set up versus integrated into the dual battery system, I believe specific to my circumstances the path of least resistance is to wire an MPPT between the solar panel(s) and th dual batteries. This is because the vehicle I purchased already has a fair amount of auxiliary electrics wired to the dual batteries (12v, two USBs, and a few LED lights in the roof tent; arb fridge; and exterior camping lights). I’d rather add solar to that existing system than re-wire everything.

 

[Gmr213]

I am leaning towards this setup:

-Today I mounted just one of the 100 watt panels to the roof rack on my roof tent (Ursa Minro J30) that I will run full time.
-I staged the wires with the MC4 connectors go from the solar panel in between the top and bottom of the tent as it shuts
-I removed the 12v from the bottom of the tent, this opens a hole into the back of the Jeep where I can run the solar wires
-I will purchase a long 10 AWG with MC4 connectors on the end I can cut to size to run from the panel, though the tent, into an MPPT I will install
-Based on the recommendations above I'll get the bluetooth Victron MPPT, I like the idea of more data to nerd out over
-From the MPPT I will run wire along the path through the Jeep where my ARB fridge wiring is already located, through the firewall all the way to the dual battery system
-My research indicates that I should connect the solar wires to the main cranking battery for the Genesis system, as this will cause the main battery to get charged and charge the aux battery in the process
-I plan to install a 30 amp fuse on the 10 AWG solar wires I am using

Any feedback?

 

[luthj]

It depends on how much you drive, but a 50qt fridge will likely need more than 100W of solar to run full time. Don't bother fusing the solar panels themselves. There is no fire risk there. Fuse the charge controllers output near the battery. Are your batteries connected in parallel full time or not? If they have some kind of combiner relay, you may want to change how you have things wired up.

If the batteries are not independent, make certain your fridges cut-out voltage is high enough to still allow an engine start. The standard cut-out on many is 10.8V, which is basically a dead battery.

 

[Gmr213]

I probably did not word it correctly but I only intend to fuse MPPT to battery as to be described. I can’t really summarize how the genesis system works so here’s a long copy from the genesis site. :

When both your batteries are fully charged at 13.2 volts, they are automatically connected and are charged at the same time.
When you park and turn off the engine, but continue to use accessories such as lights or the stereo or a CB, both batteries begin to drain down.
When your main cranking battery reaches 12.7 volts, the smart isolator separates the batteries, so that your cranking battery will have enough power to start the engine. The second battery continues to power your accessories for as long as it will last.
After you crank the vehicle, your main cranking battery will be charged up to 13.2 volts first, and then the isolator will begin charging your accessory battery. By only charging one battery at a time, your alternator is protected from excessive strain.
What if your cranking battery is somehow drained down too low to be able to start the vehicle? We have a solution for that.

Press the Start Boost button and the isolator will connect both batteries together for 1 minute, acting like built-in jumper cables to jump start your engine off your accessory battery.
As long as the accessory battery has enough power, you'll be able to start your vehicle instead of being stranded with a dead battery!
The alternator will charge both batteries for 1 minute, then switches back over to automatic mode to reduce the strain on your alternator.

 

[Rando]

One suggestion - connect your fridge to the load terminals of the MPPT 75/15, and connect the charge controller to the aux battery. The MPPT 75/15 load terminals function as a fully programmable low voltage disconnect (configurable in the Victron app) as well as monitoring the current used by the fridge. You can also turn the fridge on and off via bluetooth this way. Connecting the charge controller to the Aux battery gives you the best chance of being able to run the fridge continuously off a 100W panel. The solar will recharge your aux battery most of the way before combining with your starter battery and charging that, although it shouldn't really need to charge as it has no loads.