Solar set up on a boat

[Andrew Price]

Im wanting to create a solar system on my Sail boat. 2 rigid panels of 100 Watts each plus a Flexi panel of 150 watts.
I have three 12 volt batteries on the boat, two 85amph and one 100amph, these are connected in parallel.
Which way would it be best to connect the solar to the batterys.
1. should I connect the three panels together then into one MTTP and then out to one 12 volt battery or
2. should I be connecting three panels directly to three batterys independently through three MTTP?
When the engine is running it charges the batterys through an alternator, I also have shore power when connected on the dock but the solar is wanted for when sailing and an anchor.
Any advice would be much appreciated.

 

[Bubba1]

I would parallel the two 85amp batteries and connect to the two 100 watt panels that are connected in series. The other battery connect to remaining panel. Have a selector to connect all batteries when you're running engine or whenever you need to. I like a separate start battery from the house bank.

 

[MisterSandals]

I have three 12 volt batteries on the boat, two 85amph and one 100amph, these are connected in parallel.

This is not optimal but it sounds like it is working as a single battery bank for you. Is it your preference to have a single large battery bank? Or a separate starter and house bank?

What are the specs for your panels? Voc and Imp.

I also have shore power when connected on the dock

Do you currently charge from shore power?

 

[Wellbuilt]

I ran the Same system on my 30’ Catalina I have one solar panel in the back behind the rigging in the pic
and added a second one .and a flex panel rolled out on my boom .
I used I large house bank of 3 150 ah agm deep cycle battery’s and one regular starting battery .
the solar and 150amp Bomar alt and Shore power inverter charger all charged the house bank .
The starter battery was charged by the house bank with a eco charger that just kept it full just to start the diesel .
I used a regular morning star 20amp charge controller .
I added a hi output regulator from alternate power to charge from the alt .
The boat was on a morning for years so no shore power .
I made the solar rack out of 1” SS tube and SS fitting s
I have a old hart inverter charge in there I think hart freedom became xantrex
I would parallel the 2 85ah battery’s for the house bank and use the extra one for starting .
I ( would not )parallel all 3 battery’s and use a 123 switch Just keep the 2 banks totally separate .

 

[Andrew Price]

This is not optimal but it sounds like it is working as a single battery bank for you. Is it your preference to have a single large battery bank? Or a separate starter and house bank?

What are the specs for your panels? Voc and Imp.


Do you currently charge from shore power?

Not got the panels yet. When I’m on the dock I do connect to shore power and it charges all three battery’s.
The solar is for when away from dock.
Just need to know if I should be connecting the three pannels together then to one battery or do I have one panel to one battery.

 

[12VoltInstalls]

Just need to know if I should be connecting the three pannels together then to one battery or do I have one panel to one battery.

One mppt charge controller with three panels in parallel is preferred with your description to charge three batteries in parallel.

I assume lead acid batteries?

The ‘issue’ is that the 100Ah battery may not be fully charging due to the ‘weighted’ capacity of the 85Ah batteries. Not a safety issue but the electrolyte levels should be checked every coupla weeks (for flooded lead acid) because the two 85 batteries might experience more fluid loss. Just things you should be aware of as FYI

The other ‘issue’ is the three panels on one charge controller ‘should’ be the same or as close as possible in VOC and max amps for best results. In parallel, many people use different wattages with no ill effect, while others report not full output from higher wattage panels.

If it were me I’d use three 100W rigid/standard panels and skip the flexible panel. I’ve never met anyone raging positively about the longevity of their ‘flexible’ panels unless they were set in ‘glass or epoxy. So I’m jaded; not a flexipanel fan.

One thought more: I’m usually not one to like panels under 100W. Or monocrystaline panels for cost VS benefit.
In your case, however, the smaller format of monocrystaline and the size difference of a 50W mono panel may offer enough of a variable to make mounting the ‘third panel’ easier. If you obtain a pair of 50W mono panels (or 3 36W) that when combined in series have similar characteristics to the 100W panels those could be a good match.
I’m just thinking how to avoid a flexible panel.

 

[acdoctor]

Mast and ringing would cause shading that would affect the output. I would use 3 ridged panels each on a PWM controller. Also I would have a isolated start battery like has been mentioned previously.

 

[Andrew Price]

One mppt charge controller with three panels in parallel is preferred with your description to charge three batteries in parallel.

I assume lead acid batteries?

The ‘issue’ is that the 100Ah battery may not be fully charging due to the ‘weighted’ capacity of the 85Ah batteries. Not a safety issue but the electrolyte levels should be checked every coupla weeks (for flooded lead acid) because the two 85 batteries might experience more fluid loss. Just things you should be aware of as FYI

The other ‘issue’ is the three panels on one charge controller ‘should’ be the same or as close as possible in VOC and max amps for best results. In parallel, many people use different wattages with no ill effect, while others report not full output from higher wattage panels.

If it were me I’d use three 100W rigid/standard panels and skip the flexible panel. I’ve never met anyone raging positively about the longevity of their ‘flexible’ panels unless they were set in ‘glass or epoxy. So I’m jaded; not a flexipanel fan.

One thought more: I’m usually not one to like panels under 100W. Or monocrystaline panels for cost VS benefit.
In your case, however, the smaller format of monocrystaline and the size difference of a 50W mono panel may offer enough of a variable to make mounting the ‘third panel’ easier. If you obtain a pair of 50W mono panels (or 3 36W) that when combined in series have similar characteristics to the 100W panels those could be a good match.
I’m just thinking how to avoid a flexible panel.

That’s great info thank you very much for your guidance.