Solar & Alternator Power

[PSea]

Need some help as I begin to upgrade my trailer's power. I'm going to work on this in stages. Small steps.

My configuration:
200ahrs (2 AGM batteries) in trailer
120w suitcase solar panel w/ a PWM located at the solar panel
Solar panel has an anderson plug that connects to the trailer's anderson plug at the front of the trailer.
I believe the trailer's anderson plug wiring goes to the batteries w/ an inline circuit breaker.
I don't have any charger at present. My sole source of replenishing my batteries is solar.
Truck has a 70a densco alternator.

Goal: I want to connect the trailer's anderson plug to my tow vehicle when I'm on the road. When in camp, I'd disconnect the trailer from the truck and plug in the solar panel. I'm not expecting big amperage output from the alternator. But a few amps into the batteries to offset the cooler/fridge's consumption would be nice.

Other factors.
- I plan to upgrade the solar panel and get an MPPT controller. This wouldn't be located at the solar panel anymore. It would be in the trailer and presumably connected to the other end of the Anderson Plug cable running to the front of the trailer.

So when I plug my truck's anderson plug into the trailer's anderson plug, am I going to harm the MPPT controller? How do i go about leveraging the trailer's anderson plug to accept charging from a solar panel and my truck's alternator (not at the same time)?

 

[workerdrone]

Why use an anderson instead of charging from your trailer's lighting / braking plug?

You should just be able to wire power in from there to the battery. It won't hurt the solar charge controller.

Then use the anderson to plug in your portable solar when you can use it.

 

[dreadlocks]

use the big andersons and run a heavy gauge wire directly from alt or as good as you can and you might get a good 20A+ out of the vehicle while towing.. if you drive long distances then this can get you a full charge back from nothing in 8h of driving.

a 7 pin trailer plug through normal wiring only provides about 3-8A of power to the trailer, depending.. enough to keep fridges and stuff going while its getting baked in the hot sun but its not going to give it much of a charge and after a full day on the road you might find your battery gauge hardly moved.

MPPT wont be harmed by anything on the load side as long as its within normal 12vdc appliance spec (ie, not 18v)

 

[PSea]

use the big andersons and run a heavy gauge wire directly from alt or as good as you can and you might get a good 20A+ out of the vehicle while towing.. if you drive long distances then this can get you a full charge back from nothing in 8h of driving.

a 7 pin trailer plug through normal wiring only provides about 3-8A of power to the trailer, depending.. enough to keep fridges and stuff going while its getting baked in the hot sun but its not going to give it much of a charge and after a full day on the road you might find your battery gauge hardly moved.

MPPT wont be harmed by anything on the load side as long as its within normal 12vdc appliance spec (ie, not 18v)

EXACTLY what I intend to do. 2ga wire from battery to rear of truck where it will connect to an sb175 anderson plug. two reasons. 1) to minimize voltage drop within reason and 2) the anderson plug will also be used for a winch that I can connect to the trailer hitch.

OK, so basically, the MPPT won't care what the source of the amperage is as long as the amperage/voltage is within the specs of the MPPT controller.

Thanks again dreadlocks!

 

[dreadlocks]

Just remember to disconnect the trailer from the vehicle so your camp loads dont drain the battery, if you want you can make it switched with a big relay on the ignition to idiot proof it and ensure your vehicle always starts up in the morning.. I've heard teardroppers complain of stopping for a quick overnighter, running the fan all night and then having to jump start the vehicle in the morning because everyone was so tired they forgot to unplug the trailer. (they likely had a low battery that spent all night charging off vehicle battery + fan/fridge loads)

Also reduces corrosion on the andersons if they are not powered.. if I look on the 7 pin trailer feed to my camper all the pins look fine but the 12v always on line is green.. so I put a big diode on it.

 

[rayra]

seconding the keyed-on solenoid and fatter feed line to anderson coupling to the trailer battery for on the move charging. The MPPT isn't going to care.
IIRC the constant-hot in a typical 7-pin is fused at 10A or 15A. And the wiring is pissant gauge anyway.

 

[PSea]

Don't really understand what you guys are proposing. If I understand correctly, keeping the trailer connected to the 7pin will drain my truck's battery? Or is this problem just limited to the anderson? If the latter, would an acr resolve this or is it even simpler?

 

[workerdrone]

It shouldn't, but just stick a meter on it with truck running and then not - if the 7 pin is still hot with the truck off then it will drain your truck's batteries, yes.

The charging while running from the 7 pin isn't much but should definitely be enough to run the fridge and charge the trailer battery at a low rate. I had a trailer with only a single small 12v marine battery in it and a fridge, no solar, as long as we drove every day the setup worked.

 

[PSea]

Yup. Not legit yet. But working on it. ;-)

Might you share a link to a relay you would recommend?

 

[Hillbilly Heaven]

For the non electrical savvy.
https://www.painlessperformance.com/wc/40103

If you feel brave enough to select your own components then do a search here for cheap dual battery setup.

 

[PSea]

Thanks Hillbilly. Looking for a simpler solution as I already have the cable and connectors. Just looking for the relay to insure no battery drain on my truck.

 

[shade]

Thanks Hillbilly. Looking for a simpler solution as I already have the cable and connectors. Just looking for the relay to insure no battery drain on my truck.

There are other options, but a Blue Sea SI-ACR would be a very reliable solution at a reasonable price.

https://shop.marinehowto.com/products/blue-sea-7610-automatic-combining-relay

 

[dreadlocks]

7 pin trailer plugs should always be hot IMO, mine is not (on vehicle side of plug) and guess what flashers dont work at night if the key is not in? but if your wiring up a dedicated line, I think ignition switched would be preferable, I cant think of anything you'd want power for w/out engine running out that thing.. your going to need the alternator running for your winch too.

 

[smd3]

You should just be able to wire power in from there to the battery. It won't hurt the solar charge controller.

I’m going to try to piggyback here, rather than start a new thread. I’m planning something similar.

should I have the hot from my 7-pin go straight to the battery andlet the truck charge it? (It’s a ‘16 F150, I think it’ll charge it intelligently)
Or, should the hot from the 7-pin go to the charge controller, perhaps with a switch to switch it to the panel input when using the panel?

I’m not planning on running any additional or thicker gauge wire like OP, so I don’t think isolation to keep it from draining the truck battery is necessary. I’m not sure why I’d keep my trailer plugged into the truck when it’s parked anyway.

 

[dreadlocks]

your not really going to get much of a charge, little more than a trickle all the way back there.. but just go hot back to the battery, nice and simple.. your trailer battery also needs to be able to provide braking power in a break away situation. A charge controller would really only be recommended if your doing a dedicated line and planning on using your tow vehicle as a primary charge source.