Solar Question for charging boat batteries

[Tigerhorn]

I have a boat I keep in my dock at our lake house about 3 hours away on a lift (manual lift- no dock power). I want to rig up a solar system to keep the boat batteries charged. I am not sure of the brand or amp hours on the batteries but lets assume 100. I will find out more on my next trip out to the lake in a couple of weeks. The boat has 3 12v batteries (2 wired in series for 24v trolling motor and 1 solo 12v for engine cranking). I have a covered dock but a good southern exposure and could mount panels on the dock poles that hold up the roof and have them face south. During my research I would like to use a waterproof Anderson connector from the panel to the charge controller with the charge controller mounted in the boat and panel on the dock so I can disconnect when using boat and reconnect when in dock. My rookie questions for you all are two fold.

1. Having the 2 battery "banks" - 1 24v (2 batteries in series) and 1 12v solo - what kind of charge controller should I get? How should I wire the batteries from the charge controller? I would prefer to use just one panel and charge controller if possible even if more costly.

2. There is a battery trickle charger for AC mounted in the boat and connected to all three batteries for those times when I have the boat out of the water and can plug in to 120v outlet...should I disconnect this or will it be fine being connected even though no AC present? If it helps this charger is a marine 15 amp 5-5-5 triple bank charger. Bass Pro XPS IT - made by ProMariner

Thanks for your help!!

[Mike90250]

so, with 2 different voltages to be charged, best to have 2 isolated trickle chargers. They will maintain a full battery, but won't be easily able to recharge a low battery.

12v:
something around a 40w panel, small charge controller with EQ disabled

24v
about a 60w panel, small charge controller with EQ disabled

[Tigerhorn]

Dang, Was hoping I could get away with 1 panel and a single multiple battery bank controller (if one exists).

I will look around for appropriate panels...any suggestions? Would like to keep the size as small as possible.

Also would these MPPT controllers work? They are relatively small and could mount easily in the boat. They are ip67 rated and since they will be mounted in boat I figure they should be fine. I don't know anything about brand quality so any direction there would be great!

https://www.amazon.com/Y-SOLAR-Controller-Waterproof-Batteries-Regulator/dp/B078RJNDBM#HLCXComparisonWidget_feature_div

[Sunking]

1. Having the 2 battery "banks" - 1 24v (2 batteries in series) and 1 12v solo - what kind of charge controller should I get? How should I wire the batteries from the charge controller? I would prefer to use just one panel and charge controller if possible even if more costly.

Not going to happen, need two systems, and will not be real cheap

2. There is a battery trickle charger for AC mounted in the boat and connected to all three batteries for those times when I have the boat out of the water and can plug in to 120v outlet...should I disconnect this or will it be fine being connected even though no AC present? If it helps this charger is a marine 15 amp 5-5-5 triple bank charger. Bass Pro XPS IT - made by ProMariner

If you have AC power available, then you have no use for solar. Just use a 24 and a 12 volt AC charger. Solar is not going to save you money or do a better job. Solar just cost more and does a poor job of charging batteries.

However if you insist the way to do this is buy 3 low power cheap 12 volt battery panels and two cheap PWM controlers. Both panels and charge controller can be the exact same models. We are not talking much power assuming your boat motor charges each battery while running. If not it is going to get real expensive.

[Tigerhorn]

Not going to happen, need two systems, and will not be real cheap

If you have AC power available, then you have no use for solar. Just use a 24 and a 12 volt AC charger. Solar is not going to save you money or do a better job. Solar just cost more and does a poor job of charging batteries.

However if you insist the way to do this is buy 3 low power cheap 12 volt battery panels and two cheap PWM controlers. Both panels and charge controller can be the exact same models. We are not talking much power assuming your boat motor charges each battery while running. If not it is going to get real expensive.

I do not have Ac power at the dock...Corp of Engineers will not allow it...


The motor does charge the starting battery as far as I know (it isn't connected to the trolling batteries) but the boat is used 1-2 times a month so a system I can leave on and slowly charge will be fine. So thinking the 3 panel solution...should 2 of the panels be in series like the batteries? Sort of like this?
Capture.PNG

[Sunking]

Yes sir you got it. seeing how your trolling motors are deeply discharged, you might consider a faster charge rates because batteries do have minimum charge current requirements. Last thing you want is weak short lived trolling motors. So consider this and think about it. 12 volt battery panels are low power and cost considerably more than panels made for grid tied systems. 12 volt battery panels have 36 cells, so as you have figured out already takes two panels in series or 72 cell to charge a 24 volt battery.

So consider using a 72 cell panel made for grid tied systems. You should be able to buy say a 225 watt 72-cell panel for the same cost or less than a 36 cell 100 watt panel battery panel. You can still use an inexpensive PWM controller if you want. For the single 12 volt starting battery no need for anything more than 20 to 30 watts as its only purpose is to keep a fully charged battery charged, so no need to meet minimum charge current requirements.

Hope that helps and happy shopping.

[Mike90250]

The uber cheap way is to get 3 "maintainer" panels used off flea bay, that are used in cars while shipping overseas. VW uses and tosses many of them . They maintain a battery, will not recharge a dead one