Boat Dock Battery Charging

[groundedchevy]

I recently moved my boat to a dock without power, and I would like to use a solar panel connected to an EVPEVER dual battery charge controller to keep my three batteries charged (starter battery (12v) and 2 12v trolling motor batteries (24v)).

I planned to mount a solar panel on the roof of the dock. What is the best way to quickly connect and disconnect the solar panel from the boat when I use the boat? In my head, I would have an on/off switch or breaker mounted to the dock with a plug below it.

I also have a DC charger that will use the outboard alternator to charge the trolling motor batteries in addition to the starter battery. I thought this would help if I fished multiple cloudy days. I haven’t researched panels yet and would love a recommendation for my application.

Eventually, I plan to add an inverter to run my boat lift (currently using my F150 inverter and an extension cord). It peaks on startup around 2000 watts and runs at 1500 watts for less than 4 minutes. Is there a budget inverter that anyone would recommend for this application? The smaller, the better due to mounting space.

Any other suggestions or ideas would be appreciated.

Charge controller link:
EVPEVER 20A Solar Charge Controller 12V/24V Auto Working Dual Battery Solar Panel Charge Controller PWM 20AMP Intelligent Solar Panel Batteries Regulator for Motorhome, Caravan, Boat

 

[sunshine_eggo]

IMHO, that charge controller can't be connected to a 12V and a 24V. Both batteries must be the same voltage.

It's a PWM controller, and those work by shorting the panels to the battery, thus they must both be the same voltage. If you rewire the trolling motor batteries as 2X 12V in parallel, no problem.

I could be wrong, but I would confirm with the manufacturer that you can use two different voltage batteries. The manual doesn't specify either way.

If you can, then a single 12V/100W panel wouldn't work. You'd need a 24V panel (Voc ~45V, Vmp ~36V) to make it work, and it will perform very poorly on a 12V battery.

 

[groundedchevy]

IMHO, that charge controller can't be connected to a 12V and a 24V. Both batteries must be the same voltage.

It's a PWM controller, and those work by shorting the panels to the battery, thus they must both be the same voltage. If you rewire the trolling motor batteries as 2X 12V in parallel, no problem.

I could be wrong, but I would confirm with the manufacturer that you can use two different voltage batteries. The manual doesn't specify either way.

If you can, then a single 12V/100W panel wouldn't work. You'd need a 24V panel (Voc ~45V, Vmp ~36V) to make it work, and it will perform very poorly on a 12V battery.

That makes sense to me. So what you are saying is that I will need a charge controller and panel for each battery bank? Is there a certain one you would recommend? Any thoughts around a quick disconnect outlet to connect the boat to the panels?

 

[sunshine_eggo]

That makes sense to me. So what you are saying is that I will need a charge controller and panel for each battery bank?

Yes.

Is there a certain one you would recommend?

Cheap PWM is probably the best way to go. While I'm not a fan of renogy, their "wanderer" units are fairly inexpensive.

Any thoughts around a quick disconnect outlet to connect the boat to the panels?

XT-60 or the little SAE plugs. Since you're dealing with relatively low current, you should have some options.

 

[groundedchevy]

Why would you go with PWM over MPPT?



I've looked at quite a few Victron MPPT charge controllers on Amazon.



I read a review where someone said they used the charge controller to charge their 12v from a 24v bank. Could I use one solar panel hooked to the charge controller that is connected to the 24v bank and a charger controller from the 24v bank to the 12v?

 

[sunshine_eggo]

Why would you go with PWM over MPPT?

You started with a PWM, so I thought you were looking at budget models.

I've looked at quite a few Victron MPPT charge controllers on Amazon.

If you're willing to go Victron, HELL YEAH! I'll recommend Victron at the slightest hint of a blue breeze.

I read a review where someone said they used the charge controller to charge their 12v from a 24v bank. Could I use one solar panel hooked to the charge controller that is connected to the 24v bank and a charger controller from the 24v bank to the 12v?

PV to MPPT #1 to 24V to MPPT #2 to 12V.

Yeah. That would work. MPPT #2 would need to be fused for it's maximum PV input current limit.

Charging would favor the 12V as the 24V battery represents a much more plentiful source of power vs. the PV.

With Victrons, you can set the max charge current, which might be useful in keeping the output to the 12V manageable.

 

[groundedchevy]

Thank you for all the help!

Do you have a recommendation for the size of charge controllers? I'm looking at the smart solar MPPT 75 | 10, MPPT 75 | 15 and MPPT 100 | 15.

I'm guessing the MPPT 75 | 15 would be ideal unless I want to add multiple panels. I'm sure I could get by with the 10 amp between the banks, but it's only a $5 difference.

What are your spec recommendations for a solar panel?

 

[sunshine_eggo]

The second number is the output current. The datasheets list their maximum output power for a given battery voltage. Match that to your panel. If it's only $5 difference, 15A.

 

[groundedchevy]

Would this one be a good fit and price?

 

[sunshine_eggo]

Good "24V" panel. My perspective of price is very skewed as I live 13 miles from SanTan solar, but that's about what I paid for my Talesun 330W panels in 2019 when a few of us went in together on two pallets (54 total panels).