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Solar powered marine battery chargers

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clarythedrill
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12:49p, 2/5/26
To all, I have the opportunity to put my boat in a boat slip this year. The slip is nice but it does not have electricity on site to plug in a regular battery charger. My boat has two batteries for the trolling motor and fish finders that I will need to keep charged so the boat will be ready to fish on the weekends. I am not worried about the engine battery as it will charge while the boat is moving.

My questions are, what size wattage should I be looking at, and would it be better to have one charger for each battery? I have seen sizes from 15 watts all the way to 70. The charger(s) would have four or five days to get the batteries back charged again before usage.

I have thought about putting a switch at the main engine battery and going back and forth with the switch and let the engine charge the two forward batteries, but I really don't want to have to move around simply to charge the other two batteries, but it is an option.

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SGrem
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1:42p, 2/5/26
I posted my method before. My outboard charges all "5" of my batteries at once. Since writing the below I have gone to AGM 12v starting battery for my new motors built after 2022. Was having some weird glitchy random gremlins on my new motors with lithium starting battery. My older motors still have the lithiums.
As for your solar powered charger get the best one you can find NOT the cheapest. That will consist of heavy duty battery monitors to regulate the charge load going to the batteries. And FYI these remote location chargers is one of the best ways to come back to your boat and find it burnt down to the water line.

Batteries and chargers.
12v Lithium Pros 100ah for starting.
12v Lithium Pros 100ah for accessories.
36v Lithium Pros 60ah for trolling motor.

There are no outboard motor manufacturers that will say lithiums are ok for start. None. They allllll say DONT use em. I have been using lithiums to start Tohatsu, Nissan, Yamaha, Mercury, Etec, Suzuki for over 15 yrs. No issues. Use at your own caution. I think Lithium Pros have the best BMS (Battery Management System) to allow for best opportunity to use as starting.

Blue Seas 6011 M-Series Battery Switch Dual Circuit Plus
This switch turns both batteries on/off with one click to on/off while keeping the circuits seperated. Then there is an emergency combine if you end up with a battery problem. Its like having two seperate circuits available all the time.....with jumper cables hooked up to back up either circuit all the time at any time. It works seamlessly.

Egis 8510-1300 XD.... it is an ACR (Alternate Charging Relay) that is the correct/best one for Lithiums. It will share voltage between your two batteries keeping them both charged from the big motor. (OtherWise Blue Seas standard ACR that comes with their add a battery kit is purdy good for standard batteries.)

Power Pole Charge.
This charges the 12v starting and 36v trolling motor battery from the big motor. You can bluetooth in and set priority to one or the other or shared. Then the ACR charges the second 12v as well. So alllllll of my batteries are charged at the same time from the big motor. Additionally I can Bluetooth in and backfeed my 12v starting battery from the 36v trolling motor battery for an emergency start.

That way I have double redundancy on emergency start using all my batteries isolated but CAN be used as jumpers to the other batteries. All set up nothing to do nothing to hook up in an emergency, nothing to adjust it just works. Don't have to Additionally maintain a separate jumper box.

The 36v battery doesnt have a switch. It just stays hooked to the trolling motor. Turn the trolling motor on off. Some trolling motor manufacturers are also saying to disconnect trolling motor plug to charge. I just learned of this a couple months ago after NOT doing that for 15 yrs. Mine just stays plugged and gets charged no issues.

I leave my Power Pole Charge plugged in. If you cannot leave it plugged in you need to blue tooth in and turn it off as it will drain batteries just sitting there. It is constantly trying to equalize battery charge and if left on they will draw each other down. Mine stays plugged in. My batteries are lasting about ten years so far with no signs of slowing down.

This set up works for me. My boats are all ready to go at a moments notice after sitting however long. They are always topped up.

Even after heavy use the charge on the go for all batteries gives me all the run time I need. I have never run down or been worried. This after being on the water 220 days a year or so.
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clarythedrill
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In reply to SGrem • 2:28p, 2/5/26
SGrem said:
I posted my method before. My outboard charges all "5" of my batteries at once. Since writing the below I have gone to AGM 12v starting battery for my new motors built after 2022. Was having some weird glitchy random gremlins on my new motors with lithium starting battery. My older motors still have the lithiums.
As for your solar powered charger get the best one you can find NOT the cheapest. That will consist of heavy duty battery monitors to regulate the charge load going to the batteries. And FYI these remote location chargers is one of the best ways to come back to your boat and find it burnt down to the water line.

Batteries and chargers.
12v Lithium Pros 100ah for starting.
12v Lithium Pros 100ah for accessories.
36v Lithium Pros 60ah for trolling motor.

There are no outboard motor manufacturers that will say lithiums are ok for start. None. They allllll say DONT use em. I have been using lithiums to start Tohatsu, Nissan, Yamaha, Mercury, Etec, Suzuki for over 15 yrs. No issues. Use at your own caution. I think Lithium Pros have the best BMS (Battery Management System) to allow for best opportunity to use as starting.

Blue Seas 6011 M-Series Battery Switch Dual Circuit Plus
This switch turns both batteries on/off with one click to on/off while keeping the circuits seperated. Then there is an emergency combine if you end up with a battery problem. Its like having two seperate circuits available all the time.....with jumper cables hooked up to back up either circuit all the time at any time. It works seamlessly.

Egis 8510-1300 XD.... it is an ACR (Alternate Charging Relay) that is the correct/best one for Lithiums. It will share voltage between your two batteries keeping them both charged from the big motor. (OtherWise Blue Seas standard ACR that comes with their add a battery kit is purdy good for standard batteries.)

Power Pole Charge.
This charges the 12v starting and 36v trolling motor battery from the big motor. You can bluetooth in and set priority to one or the other or shared. Then the ACR charges the second 12v as well. So alllllll of my batteries are charged at the same time from the big motor. Additionally I can Bluetooth in and backfeed my 12v starting battery from the 36v trolling motor battery for an emergency start.

That way I have double redundancy on emergency start using all my batteries isolated but CAN be used as jumpers to the other batteries. All set up nothing to do nothing to hook up in an emergency, nothing to adjust it just works. Don't have to Additionally maintain a separate jumper box.

The 36v battery doesnt have a switch. It just stays hooked to the trolling motor. Turn the trolling motor on off. Some trolling motor manufacturers are also saying to disconnect trolling motor plug to charge. I just learned of this a couple months ago after NOT doing that for 15 yrs. Mine just stays plugged and gets charged no issues.

I leave my Power Pole Charge plugged in. If you cannot leave it plugged in you need to blue tooth in and turn it off as it will drain batteries just sitting there. It is constantly trying to equalize battery charge and if left on they will draw each other down. Mine stays plugged in. My batteries are lasting about ten years so far with no signs of slowing down.

This set up works for me. My boats are all ready to go at a moments notice after sitting however long. They are always topped up.

Even after heavy use the charge on the go for all batteries gives me all the run time I need. I have never run down or been worried. This after being on the water 220 days a year or so.


Well I have wondered what would happen if a solar charger malfunctioned and what the result would be, and burning down my boat and the slips and any other boat there would not be ideal. I think I will install one of the above relays and just plan on running the engine more than planned to keep a good charge in all the batteries. Thanks for the info.
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Gunny456
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In reply to clarythedrill • 3:23p, 2/5/26
AG
Your problem is not a unique one. Lots of boat lifts and slips don't have on shore power. We have customers that have used products made by a company called Lake Lite. Link provided below. They aren't cheap but they make excellent turn key systems that are specifically for marine environment use.
Using the proper equipment and installed correctly these solar charging systems are not anymore a risk than 120volt onboard systems are.
Suggest you talking to these folks.
https://lakelite.com/
TAMU Wildlife & Fisheries Sciences

"Boat Racing is like a beautiful woman.... expensive, high maintenance....... but well worth the fun!"
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RethinkTheWeekend
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4:22p, 2/5/26
AG
Gunny and Grem with some crazy boat knowledge. Appreciate both of you guys.
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Gunny456
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In reply to RethinkTheWeekend • 4:25p, 2/5/26
AG
With 40 years of making my living in the marine business I just try and hope I can maybe help folks with boat stuff in some way. Especially Aggies.
TAMU Wildlife & Fisheries Sciences

"Boat Racing is like a beautiful woman.... expensive, high maintenance....... but well worth the fun!"
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SGrem
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6:03p, 2/5/26
Fishing 220 days a year or so and on the boat duck hunting another 30 or so.... I need things to work....every day....no matter what. And be easy to maintain and keep up. I have three charter boats and two more I dont charter out of. They are all set up the same and they all work every time I get in em.... so the formula above gives me a lot of confidence.

But usually Gunny is more correct than I am so for sure follow his advice and then take mine w a grain of salt. Lol
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Gunny456
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In reply to SGrem • 7:04p, 2/5/26
AG
Your knowledge and advice is from hands on use. Don't want to take that with a grain of salt.
TAMU Wildlife & Fisheries Sciences

"Boat Racing is like a beautiful woman.... expensive, high maintenance....... but well worth the fun!"
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fullback44
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7:46p, 2/5/26
AG
OP - I'm with you I spend a lot of money to keep my bigger fishing boat in a dry dock in Kemah- the problem is the city of Kemah won't let them keep 110V lines plugged into our boats when inside the dry dock. They have to pull m the boat a day before and plug it in- the problem is if you don't go check it you may have bad batteries sometimes - it's killing my batteries by not keeping a charge on those batteries

Nothing I can do except deal with it every time we run the boat - not ideal but city of Kemah has their rules
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Mas89
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9:35p, 2/5/26
AG

Looking for a solar charger to leave at my pond. Regular Walmart 12 v deep cycle battery. Tired of taking it out to charge and back.
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normaleagle05
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In reply to Mas89 • 10:15p, 2/5/26
AG
I'm curious what your reasons are for this. Guessing you need a tool to disconnect the terminals and the battery is heavy.

If you swap the terminal connections for some Anderson connectors and buy a lithium battery it'll solve both of those problems. Then you'll have an easy to transport battery that can also do other things. Probably cost similar to buying a decent solar setup and will eliminate weight in the boat and the reliance on a crappy Walmart lead acid battery.
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Mas89
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In reply to normaleagle05 • 10:42p, 2/5/26
AG
Yes, mainly the weight of the battery. Main access is with a utv and it's often wet/ lots of gear to transport. No problem disconnecting- I keep pliers in the boat.

I've never been around a boat use lithium battery. Are they that much lighter/ longer lasting per charge? We've always used the larger standard deep cycle battery. I don't mind investing in better tech if it would help.
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SGrem
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10:49p, 2/5/26
Yes they are that much lighter. 20 pounds for lithium vs 70 pounds for lead acid. Or there abouts.....

They maintain charge longer. They charge faster. Remain charged in long term storage. Longer life of ten years or more. And more useful charge.... (where a lead acid battery will start to get weaker and weaker under 60% charge or so....lithiums will give full power down to 10% charge or so.)
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Mas89
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In reply to SGrem • 10:56p, 2/5/26
AG
Wow that's a huge difference. Especially when I move around and fish different ponds same day. The trolling motors are minn kota riptide 45. I assume the lithium battery will work with the riptide model.

Best place/ brand lithium to buy? Size? Lithium battery charger? Bass pro is not too far away.
Thanks.
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Gunny456
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In reply to Mas89 • 11:08p, 2/5/26
AG
Minn Kota builds multi bank chargers that have a lithium selection mode. NOCO charges do as well.
There are numbers of brands of lithium batteries but the cells in them are all basically built in China by a couple of companies.
The difference in brands are the battery management systems and warranty. Read the warranty closely as they can be deceiving.
Yes you can use them on your Rip Tide but Minn Kota will caution you on running it on the high setting for any length of time because lithiums put out more voltage than AGM or lead acid. You can overheat the motor on high too long.
The only negative on lithium is they recommend not charging them below freezing unless the brand you get has the internal heaters within the BMS system. Most brands do not.
TAMU Wildlife & Fisheries Sciences

"Boat Racing is like a beautiful woman.... expensive, high maintenance....... but well worth the fun!"
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Gunny456
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In reply to Mas89 • 11:21p, 2/5/26
AG
We OEM with Dakota, Ionic, Millertech and Lithium Pro. Lots of our pro fisherman use Battleborn and Ionic.
One thing that a lot of guys that fish tournaments have got away from recently is buying the 36v batteries as a single battery.
Only because if they fail they are not readily available at dealerships and then they are totally down. They are opting to go with individual 12 volt batteries so if they lose a battery it's easy to find 12v lithiums just about anywhere and they can keep fishing.
Just a thought.
TAMU Wildlife & Fisheries Sciences

"Boat Racing is like a beautiful woman.... expensive, high maintenance....... but well worth the fun!"
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normaleagle05
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In reply to Mas89 • 11:31p, 2/5/26
AG
And because of the additional depth of discharge, depending on your use case, you could get away with a dimensionally smaller lithium battery. I have a Minnkota and a 65ah lithium for my field crew to do bathymetric surveys in a 1436 aluminum boat. It'll push 2 guys at 250lbs each and other minimal gear around all day.

I'd still invest the minimal cost of an Anderson connector to make it that much easier to unplug and to be able to plug other things in easily. But I do a lot of 12v wiring and have tools/supplies laying around for it.
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Mas89
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7:26a, 2/6/26
AG
Thanks guys. I feel like a cave man that just discovered fire. Got my first aluminum boat for my 10th birthday and then a trolling motor the next year so I've been lugging a heavy battery around fishing/hunting for 48 years. Often on wet, slippery reservoir banks. I've seen y'all mention lithium batteries but never knew they were lighter.
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SGrem
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8:11a, 2/6/26
I have a 36v Lithium Pros 30amp hour and a Garmin Kraken on 21ft Lund. Fishes a group of 3 or 4 all day.

When its just me on a leisurely fishing trip to the in laws lake house on lake LBJ and the way i have it set up to charge on the run it will run the whole 3 day weekend without a charge just fine.

Big guide boat has 36v 60 amp hour and Garmin Kraken. Ive never run out of juice. Even in a 26ft boat with 9.5ft beam giant oversized Ttop full of customers in heavy wind and current on the coast. Boat motor and trailer is 7000 pounds.
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roynonroy
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8:42a, 2/6/26
OP - You don't mention what motor you have. The "charge on the run" solutions are dependent on the amp output of your outboard.
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RethinkTheWeekend
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11:47a, 2/6/26
AG
6 seater golf cart - replaced 6 lead acid batteries with one lithium ion battery last month (it is a big battery) but it reduced the weight by almost 300 lbs.
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SGrem
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In reply to RethinkTheWeekend • 2:27p, 2/6/26
RethinkTheWeekend said:
6 seater golf cart - replaced 6 lead acid batteries with one lithium ion battery last month (it is a big battery) but it reduced the weight by almost 300 lbs.


Same here for my 48v Deere Gator replaced 8 big honking lead acid golf cart batteries with 4 lithiums and removed over 300 pounds off that frame.....
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clarythedrill
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In reply to roynonroy • 4:16p, 2/6/26
roynonroy said:
OP - You don't mention what motor you have. The "charge on the run" solutions are dependent on the amp output of your outboard.

Its a 150 Mercury, so the output from the alternator is 60-65 amps. Not sure how much trolling around simply to charge the batteries would be needed, but I would assume more than just a short hop to the fishing spot.
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Gunny456
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In reply to clarythedrill • 3:25a, 2/7/26
AG
Just FYI. Depending on the year model of your Merc 150, Mercury makes an upgrade alternator kit that gives you greater amperage output.
Here is the link to the Mercury product bulletin on them and some other good info included. https://www.mercurymarine.com/us/en/lifestyle/dockline/the-mercury-alternator-advantage--more-power--more-fun--

TAMU Wildlife & Fisheries Sciences

"Boat Racing is like a beautiful woman.... expensive, high maintenance....... but well worth the fun!"
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clarythedrill
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In reply to Gunny456 • 8:10a, 2/7/26
Gunny456 said:
Just FYI. Depending on the year model of your Merc 150, Mercury makes an upgrade alternator kit that gives you greater amperage output.
Here is the link to the Mercury product bulletin on them and some other good info included. https://www.mercurymarine.com/us/en/lifestyle/dockline/the-mercury-alternator-advantage--more-power--more-fun--


Thank you for the info Gunny, it is appreciated.
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Gunny456
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In reply to clarythedrill • 3:37p, 2/7/26
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