School me on solar for a trailer

[Eman85]

I don't know if this is the correct forum but seems to be plenty of knowledgeable people on here.
What I have is an enclosed car trailer and what I'd like to do is have solar to use for battery maintainers. I have a 12v battery on the trailer itself for winch and trailer jack, a 12v scooter and a car. Any suggestions on a simple system for a simple person?

 

[mellow]

Harbor Freight sells a briefcase setup that is easy to install. Wait for a good 25% coupon and snag one.

https://www.harborfreight.com/100-watt-solar-panel-briefcase-57991.html

Those panels hooked up to a charge controller:

https://www.harborfreight.com/lawn-garden/outdoor-living/solar/30-amp-solar-charge-controller-68738.html

 

[ABMax24]

Personally I'd go hardwired, a solar panel, mppt charge controller and some wiring is really all you need.

I have my fifth wheel setup this way to keep the batteries charged in storage and while I'm using it.

 

[Montanalocal]

I posted an entry about my simple solar battery powered setup. I would change my post to call for a 100 watt solar panel and a newer 1500 watt inverter.

Scary Power Outage

 

[peakbagger]

If you want 110 VAC its different system. The absolute bare minimum 12 volt system doesnt even need a charge controller as typically a 12 volt panel is not going to overcharge a large battery. Ideally you want a PWM (Pulse WIdth Modulated) charge controller with a Low Voltage Disconnect. This keeps the battery charged and ensures that it does not get over discharged. A MPPT (Maximum Power Point Tracking) charge controller with Low Voltage Disconnect will give a slight increase in charging efficiency but its usually not worth the extra cost.

 

[hearthon]

I went for a simple 12v Coleman panel from canadian tire 150 watt. 100ah battery from Wal-Mart and bought the charge controller off of Amazon along with the fuse box. Everything was pretty cheap and runs my entire shed.

 

[Eman85]

Personally I'd go hardwired, a solar panel, mppt charge controller and some wiring is really all you need.

I have my fifth wheel setup this way to keep the batteries charged in storage and while I'm using it.

I would want a panel I could leave on the trailer, is your mounted on the roof? So a panel and a controller and I could keep 3 batteries up?

 

[peakbagger]

Keeping three batteries up complicates things. Batteries in parallel tend to go out of balance as their internal resistances change slightly. One battery ends up hogging all the charge. There is e method called equalizing the batteries manually to force them into balance but it requires a high current source. In that case it may be worth switching the solar between the individual batteries.

 

[ABMax24]

I would want a panel I could leave on the trailer, is your mounted on the roof? So a panel and a controller and I could keep 3 batteries up?

Yeah, my panel is mounted on the roof. I built the bracket in the picture below. I've got a 310 watt panel and a Victron Smart Solar 100/20 MPPT charge controller. It charges 2 6volt L16 batteries wired in series.

Victron makes a Smartsolar 75/15 that would probably work with your setup and a single panel. It would more than keep up with 3 batteries.

The Victron controllers (the Smart Solar line) are Bluetooth configurable, and can be setup to equalize charge your batteries. Contrary to popular belief, you don't need a high output charger to equalize battery cells, they just need to be at full charge when the equalize function starts. I have mine setup to automatically equalize the batteries every 30 days.

 

[zrock]

Im just running a 100amp solar panel hooked up now to a Victron solar controller charging 2 6v on my travel trailer and keeps them up no issue. If i had to do it again i would go with another controller as the victron failed in less than a month and its taking forever to get a warranty replacement and this seems to be a common issue with them

 

[peakbagger]

Im just running a 100amp solar panel hooked up now to a Victron solar controller charging 2 6v on my travel trailer and keeps them up no issue. If i had to do it again i would go with another controller as the victron failed in less than a month and its taking forever to get a warranty replacement and this seems to be a common issue with them

Wow I want to see a 100 AMP solar panel hooked up to anything. My guess is a 100 Watt panel?

BTW Morningstar charge controllers are the gold standard for durable gear, they are hard to kill.

 

[Eman85]

Thanks to everyone for the info. I have not looked into solar at all before but it would just make sense. my trailer sits out in the sun all of the time. Keeping up those batteries would be nice without having to run a line to the trailer and using battery tenders. As I said I have no experience with solar so this will be a learning thing.

 

[ABMax24]

It's really straight forward, negative and positive wire from the panel to the charge controller, and a negative and positive from the charge controller to the battery. Ideally you'd put a fuse in the system somewhere, right off the positive side of the battery is probably best.

 

[zrock]

Wow I want to see a 100 AMP solar panel hooked up to anything. My guess is a 100 Watt panel?

BTW Morningstar charge controllers are the gold standard for durable gear, they are hard to kill.

Ya i guess you are right... wopps...
Wish i would have known about that controller in the beginning.. The RV Forum im on everyone was raving about them, now that i have one and started digging deeper im finding they have more problems than good.. A month later im still waiting for a resolution

 

[ABMax24]

Ya i guess you are right... wopps...
Wish i would have known about that controller in the beginning.. The RV Forum im on everyone was raving about them, now that i have one and started digging deeper im finding they have more problems than good.. A month later im still waiting for a resolution

That's the biased way of internet reviews, the tens of thousands of Victron customers without issues don't say anything, but the few dozen with issues can make a lot of noise on the internet.

I haven't had any issues with any of my Victron components, and Victron remains a very popular brand in Europe.

BTW, which model of controller do you have?

 

[zrock]

i really have to have more coffee in the morning.. i have a Renogy controller not sure why i put down Victron..

 

[peakbagger]

Renogy is relabeled chi com gear. Victron has a great rep but its "different" Sort of Volvo versus Chevy

 

[semipro]

The issue @peakbagger raises below is what complicates things. Everything else you're talking about doing is relatively simple.

Keeping three batteries up complicates things. Batteries in parallel tend to go out of balance as their internal resistances change slightly. One battery ends up hogging all the charge.

There are devices available that address this problem by isolating each battery from the others when charging is not occurring. They basically connect the batteries in parallel when the voltage at the source battery reaches a certain threshold, and then disconnect the batteries when the voltage drops below another threshold value.
Use of one or more of these may be simpler than trying to balance batteries permanently connected in parallel, especially when the size and age of the batteries differ.

Cyrix Battery Combiners | Victron Energy

Automatically connect batteries in parallel when one of them has reached a pre-set voltage using the Cyrix Battery Combiners. Find a dealer near you.

www.victronenergy.com

Cheaper versions are available on Ebay.

If you really want simple though, Its probably easier to install a separate small 12v solar charger for each battery you're charging. Something like this (not a recommendation for a specific model though).

Amazon.com

 

[gruesome]

During the pandemic I used a 100W panel and a charge controller to keep my car battery alive; initially started with a 25W panel, but that didn't do the job. It's really straightforward. Good luck!
The parts I used:
https://www.amazon.com/gp/product/B08SVXMK3V, now only $70
the 25A solar charge controller I bought is no longer available, but there are plenty of similar ones.

 

[Eman85]

Thanks for the info. For the price of some of these panels with controllers it's cheap enough to add a panel for additional batteries. Just wonder about the quality of the controllers and if they would overcharge a battery over a period of time. It seems like a cheaper way to maintain my lawnmower and tractor batteries instead of having 100v battery maintainers.

 

[gruesome]

You program those controllers, at least the one I have. Presets for different battery types, and you can fine tune the maximum output voltage. You can also program the voltage threshold under which the load is dropped off to protect the battery (if you connect the load through the controller).

 

[zrock]

Thanks for the info. For the price of some of these panels with controllers it's cheap enough to add a panel for additional batteries. Just wonder about the quality of the controllers and if they would overcharge a battery over a period of time. It seems like a cheaper way to maintain my lawnmower and tractor batteries instead of having 100v battery maintainers.

Personally for the lawnmower and such batteries i would just stick with a maintainer.. Watching the sales i got a good maintainer that does 4 units so i have it permanently mounted in the shop and my toys stay on it all winter.. FOr me to do solar for those toys would be easily double the price and then i have to find good places to put the solar panel. I have good solar lights around my property as well and well in the winter they suck as their is not a good amount of daylight to keep them fully charged and always have to remove the snow from them.. The whole purpose of putting the solar in was to have light outside during the winter, instead i now wired up some LED string lights on a timer for winter use.. So if you were using solar to maintain your battery's in the winter you may not be impressed with the end result.

 

[Eman85]

@zrock I live in TN, little snow and plenty of sun in the winter. I'm not going to scrap all of the maintainers I have now but it seems like a solar charger is worth looking into. I'm going to start with 1 and see how it works out. My enclosed trailer sits away from my building and it has an onboard battery, a scooter with a battery and my car in it. Sure would be easier to have the solar keep the batteries up.

 

[gruesome]

I should add that I put together the small solar setup because there was no outlet near my parking spot. For a while during the pandemic I actually had the panel mounted between the roof rails of my car. The controller was mounted inside the car behind a rear window so I could check the charging status from the outside (didn't use the car much in those days).