Solar will keep you batteries charged because they are set up with a controller that adjust the charging to fit the demand. I use a solar panel to keep my battery topped off on multi day fishing trips and it would work in storage too but don't need it there. Lots of options so maybe someone will have a more specific answer.

 

Depends on how fast you need the trolling motor batteries charged as to how much solar panel you require. To maintain boat batteries, not many watts required, but to charge trolling motor batteries in a day, a lot of watts required. Look at the RV setups. 200 watts seems to be sufficient to maintain batteries in an RV with normal use. If your trolling motor battery is a 100 AH battery and you use 50%, say 20 amps for 2.5 hours. That is 20x12=240 watts time 2.5 hours is 600 watt-hours. To recharge those batteries a 240 watt panel is going to take more than 2.5 hours as there is not 100% efficient power conversion. if you only fish two days a week, and let the batteries charge over the other 5 days, 240 watts should be sufficient. Probably okay for 2 batteries, but a 36v system may need more solar. Non- scientific estimate.

 

Depends on how fast you need the trolling motor batteries charged as to how much solar panel you require. To maintain boat batteries, not many watts required, but to charge trolling motor batteries in a day, a lot of watts required. Look at the RV setups. 200 watts seems to be sufficient to maintain batteries in an RV with normal use. If your trolling motor battery is a 100 AH battery and you use 50%, say 20 amps for 2.5 hours. That is 20x12=240 watts time 2.5 hours is 600 watt-hours. To recharge those batteries a 240 watt panel is going to take more than 2.5 hours as there is not 100% efficient power conversion. if you only fish two days a week, and let the batteries charge over the other 5 days, 240 watts should be sufficient. Probably okay for 2 batteries, but a 36v system may need more solar. Non- scientific estimate.

I usually only fish one day a week so it doesn’t need to be blazing fast.


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Check out Will Prowse's videos on Youtube. He's a young solar energy enthusiast who makes a ton of DIY content about solar, from powering RV's to full home charging systems.

I have 200 wats of panels on my truck camper, and in the summer it is plenty to recharge a depleted series 27 deep cycle in a day. 400 watts is the minimum I'd want for charging multiple deep cycle batteries reliably and quickly with it (in winter, with short days and the sun lower on the horizon you need more panels to achieve the same result). A charge controller will prevent it from over charging your batteries.

Decent panels are relatively cheap these days... you could build out a 400 watt system + a good charge controller for about $500. Figure some extra $$ for wiring, a disconnect switch, fuses, and any structure you build to house it (maybe it's just going on your barn roof?). Looking at Amazon, you can buy a Renogy (good brand) 400 watt package w/ a basic 30 amp PWM controller for $517 right now.

 

How many batteries? For 2 series 24's, 200 watts would be fine if you are going a week between uses. $235 on Amazon right now for a Renogy kit w/ 2 100 watt panels, a 30 amp charge control and brackets/connectors. 30 amp controller is big enough to add more panels later if you need to.

 

Don't forget volts.

 

I have almost 800watts of solar panels in our RV, but realistically it's more like 600watts with dirt on panels sometimes. Wattage is ok, it's amps that matter. I use residential panels, they put out 36v@ 7amps each and have a larger surface area. With 3x panels my charge controller can kick out a solid 20-25 Amps per hour depending on state of charge and how much sun exposure. I can charge my 24v batteries in RV and boat usually in few hours. They are both lithium by the way so they charge really fast. I use a mppt charger to take advantage of residential panels.
Look on Craigslist, I bought a mix of 280w panels for 100$ each, then use a mppt charge controller, neat thing about mppt controller is it will use the max amps from panel at 24-28v then the extra volts it will convert to amps. Your 250w panel with 7amp will be 10amps sorta in best case. Also they can be configured for 12/24v and go for about 75$ on Amazon. Will need good mc4 connectors, fuse or premade wires too. Figure 250$ get you a decent setup, the mppt will have charge profile so you don't burn up batteries.
must be southern ID, when I'm in north of CDA we don't get squat for sunlight.
one down side to this is, the charge controllers need to be connected to a battery before panel. So you will want to make sure when connecting and disconnecting you have a sequence down.

 

I’d spend a little more to get an MPPT charge controller over a PWM for what you’re trying to do. I have Victron units in my RV and will soon have one in my truck for the house battery that runs my fridge.

With the 24V, you may likely benefit from running panels in series, as most charge controllers won’t start feeding a battery in its current charge state is within 5V of PV output. Many panels have an open voltage max of around 20-25 volts, so you start out in a pickle! Series the panels to double the voltage…. But, you’ll lose efficiency relative to panel exposure. Since the panels feed through each other (poor choice of words to explain) in series, you’ll see a significant reduction in performance if part of a panel is obstructed from sunlight. This could be partially avoided by running 4 smaller panels. Series pairs for the voltage, and parallel those go the controller.

Solar is really cool stuff, but there is a lot to learn if you want to get the most benefit from it.

I learned a ton by talking to the folks at AM Solar in Springfied for my truck system. They were very helpful and answered every question I had to help put together a fairly simple system that will do the best it can with the limits I need to work within. Prices were same as standard list prices, and they had everything in stock.

 

In my opinion, consider a 100W+ RV solar panel connector with a charge controller. Connect it directly to your batteries or use a portable solar generator. Aim for a marine-grade solar panel for durability. Add a voltage regulator to prevent overcharging. Secure panels well and angle them for optimal sunlight. For recharging trolling motor batteries, check the voltage requirements and use an appropriate solar setup. Best wishes.

 

Two cents from a breed blind retriever guy.
I would second the Will Prowse suggestion.
You didnt say if it your using lithium or other? Though not sure if the would make a huge difference other than Lithium provides about 50% more usable amps.
If your using a decent lithium battery , you dont need to worry about the charge controller, good lithiums have a BMS, "battery management system" . It will control charging levels., cut off charging if its below freezing and stop if its an over heat situation.
If you're using lead acid or?? get the solar charge controller.
I would also recomend the following. Its a system monitor with blue tooth so you can see your batt staus on your phone. Blue tooth range isnt great, but totally acceptable. Check to make sure it works with your system voltage.
https://www.amazon.com/TBD-SmartShu...78223&sprefix=victron,aps,222&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

This is really neat because you can monitor all types of things in your system . It can tell you power usage and battery charge stats. I noticed my RV system was using about 8 more amps than normal . so I started investigating and found my emergency brake activator on the trailer got pulled out.

As mentioned, your panels need to be clean, any shadows on panel will kill output. Heat affects efficiency.
I have never seen full output from my two panels. about 80% ?

Even if my panels put out the full 10 amp rating, they wont charge at that rate the whole time. As the battery gets full its gets harder to to charge, think of it as pressure increasing.

You can run an RV with 200 watts. But only in the right conditions, If its cold and your running your heater, you will likely have to run a generator.
Probably more than you need to know to answer your question?????