Confused about the complicated world of solar for my trailer

[sfbaytom]

Hi everyone, I'm new here. I did some searching first, didn't quite find the answers I was looking for, so decided to post.

I bought a trailer (2018 Shadow Cruiser) earlier this year and replaced the old battery with 2x6v 220aH AGM batteries in series. I plan use it for occasional camping trips, sometimes off-grid. I would love some advice here.

I have 2 levels of investment I'm considering.
1) Find a way to keep the batteries topped up and in good condition when I'm not using the trailer (it sits not plugged in, sometimes for a month or more at a time).
- I'd like to find a good way to do this. I was thinking a cheap, small solar panel (3W?) wired into a simple solar charge controller, would keep it topped off. But then I read something online about how at least 10W is needed, and then something else about multi-stage chargers, and I started to feel out of my depth.
- Would my proposed solution work or am I missing something?
- What would you recommend for keeping the batteries charged and in good condition in this setting?

2) I'm thinking of going all the way and having panels fitted to the roof so I can get a decent charge in a winter California day.
- If I do this, do I need to replace the charger that came with my trailer? Would this be the perfect opportunity to get an inverter/charger added so I can use a little 120v power when not plugged in?
- What else do I need to consider when planning a solar system? I want to make sure I get all the components right, not just the panels.
- Obviously once this is done, I won't need to worry about the trickle system I mentioned above, but I'm not sure if I want to do this yet.

Thank you so much for any help you can offer.
Tom

[SunEagle]

Hello sfbaytom and welcome to Solar Panel Talk

I understand you want to stay low in cost but with a 12V 220Ah battery system you will need about 22 charging amps. With an MPPT type charger that will require about 300 watts of panels. So you can pretty much forget that 3W or 10W because they won't do much for you even keeping your batteries in float mode.

[NCmountainsOffgrid]

a simple 100w solar panel will work just fine, with a simple controller.... don't overthink it, your're just wanting to maintain the battery, not really to 'use' it.
There are plenty of packages online that include the panel, controller, wiring, and even mounting tabs....easy.
Just attach the output of the controller to your Positive and Negative battery post and you're done.


otherwise, just pull your post connections from your batteries when you're not using the camper, and you'll not even need any solar : )

[SunEagle]

a simple 100w solar panel will work just fine, with a simple controller.... don't overthink it, your're just wanting to maintain the battery, not really to 'use' it.
There are plenty of packages online that include the panel, controller, wiring, and even mounting tabs....easy.
Just attach the output of the controller to your Positive and Negative battery post and you're done.


otherwise, just pull your post connections from your batteries when you're not using the camper, and you'll not even need any solar : )

A 100watt panel can "maintain" a battery system but I really think the OP will need more wattage to properly recharge the 220Ah system. Unless they have another way of getting to a deep charge, 5 amps from that 100w panel will not do it.

[MichaelK!]

The first important question that should have been asked is whether the solar system was to charge a depleted battery, or to maintain a fully charged battery previously filled by another charger?

If no other method of charging was available, then SE's advice is correct. Your statement (it sits not plugged in, sometimes for a month or more at a time) implies there is no other charging method. Later, you mention "do I need to replace the charger that came with my trailer?". That leads to..., what is the trailer's charger, and why aren't you using it?

I would lean towards SE's advice, because once you're out on a trip, you'll have a reliable charging system up and running that you won't have to worry about plugging in. Knowing what you're working with results in getting better advice.

[sfbaytom]

Thanks everyone.

Based on this advice and other research I'm planning to prep myself for proper boondocking and go for 2x180W panels on the roof (professionally installed).

Would a battery monitor be necessary too? I have heard this is useful. Also, do I need an MPPT charge controller for this kind of setup?

[SunEagle]

Thanks everyone.

Based on this advice and other research I'm planning to prep myself for proper boondocking and go for 2x180W panels on the roof (professionally installed).

Would a battery monitor be necessary too? I have heard this is useful. Also, do I need an MPPT charge controller for this kind of setup?

Usually any time your panel wattage exceeds 200w an MPPT CC will generate more charging amps then a PWM type CC.

Having a battery monitor is a nice addition to a system but you may get more out of a good DC voltmeter.

[Paul Land]

Thanks everyone.


Would a battery monitor be necessary too? I have heard this is useful. Also, do I need an MPPT charge controller for this kind of setup?

Just add SPDT switch on your RVs existing batt monitor. A. position RVs Batts B. position Solar Batts