Solar Panels?

[nautibake]

Was thinking of adding flexible solar panels on aft bimini to augment inverter bank. Did several searches here and did not find anything on the topic. Would be grateful for any insight or suggestions from the experts here! Thanks in advance...
Jerry

[Pascal]

I don't think the flexible panels are as efficient as the rigid ones but i haven't seen looked at them in a while.

While I use a small rigid panel (18"x24" or so) to keep my 26' sailboat charged as it is on a mooring when it comes to our boats they don't produce enough power to really make are a difference.

Do the math to see how many A/H you will get in an average day. A 100w panel will produce about 6AH an hour in th best conditions... full sunshine, panel facing the sun, etc... in the real real world you ll get 20 to 25 AH a day back in your inverter bank. Compared to the typical inverter charger rate of 100A that panel will save you about 15 minutes of generator time a day. At $2 a gallon... you ll save 50 cents a day per 100W panel which at $200 a piece means it will take 400 days on the hook to make up the cost.

Crude math that could be a bit off but you get the picture

[Scarlett]

Check out Home Depot and Grape Solar panels, depending on what sales are going on they are about $130.00 each for a 100 watt panel. We have 4 of them wired in groups of 2 directly to the 32 volt batteries. A so called 12 volt panel actually puts out about 18 volts so together you get 36 volts which is fine for a 32 volt bank. Chances are you will be drawing more than you are putting in most of the time. Our system runs 2 refers and numerous electronic chargers completely during the day with a little gain. I find that they cut my generator time in half while on the hook. John

[nautibake]

I don't think the flexible panels are as efficient as the rigid ones but i haven't seen looked at them in a while.

While I use a small rigid panel (18"x24" or so) to keep my 26' sailboat charged as it is on a mooring when it comes to our boats they don't produce enough power to really make are a difference.

Do the math to see how many A/H you will get in an average day. A 100w panel will produce about 6AH an hour in th best conditions... full sunshine, panel facing the sun, etc... in the real real world you ll get 20 to 25 AH a day back in your inverter bank. Compared to the typical inverter charger rate of 100A that panel will save you about 15 minutes of generator time a day. At $2 a gallon... you ll save 50 cents a day per 100W panel which at $200 a piece means it will take 400 days on the hook to make up the cost.

Crude math that could be a bit off but you get the picture

Thanks Pascal - although I was not approaching it entirely from an ROI perspective, that is a pretty terrible return. I appreciate your perspective, I guess that explains why I didn't find many instances of Q&A posted on HOF. Genny is looking better and better every day...

[nautibake]

Check out Home Depot and Grape Solar panels, depending on what sales are going on they are about $130.00 each for a 100 watt panel. We have 4 of them wired in groups of 2 directly to the 32 volt batteries. A so called 12 volt panel actually puts out about 18 volts so together you get 36 volts which is fine for a 32 volt bank. Chances are you will be drawing more than you are putting in most of the time. Our system runs 2 refers and numerous electronic chargers completely during the day with a little gain. I find that they cut my generator time in half while on the hook. John

Thank you Scarlett - that is pretty much what I was hoping to achieve (cut down significantly on GenSet time). It wasn't really to save fuel or GenSet time although that would be nice. More from a convenience and flexibility perspective.

My inverter bank is 24 volts (very interesting how you were able to configure the 12V panels for 32!). Would you mind sharing your approximate performance metrics in comparison to Pascal's

in the real real world you ll get 20 to 25 AH a day back in your inverter bank.

?

Thanks again!!
Jerry

[Boatsb]

Propped systems use higher voltages from the panels and send it to a charge controller that puts it to the batteries.

I did a sailboat with a 12 volt house and inverter bank but brought 48 volts or so from the panels to the controller.

It was integrated to the inverter and control system with safety lockouts and solenoid to shut down unnecessary equipment should the battery run below a certain preset point.

[Scarlett]

I think Pascal's example was with one 100 watt panel obviously with 4 panels things are much better. The other advantage to the solar is your voltage stays up all day and you almost never approach a critical voltage level. We have to run our generator for cooking so that is when we charge. Once a day is plenty. John

[jrbrein]

When we lived aboard our sailing catamaran I had (10) 75 watt rigid solar panels mounted on the hard top over the cockpit. The only time the solar panels were useful was when we were living on the hook for extended periods in the Bahamas and the Florida Keys. The panels provided us power to run the DC watermaker, DC refrigeration and cabin lights. Otherwise the genset was our primary energy source since I needed to match the load to run our air conditioning and battery charger.

So...as it turned out, those expensive solar panels served as a backup only in the case of a fried battery charger and/or the generator having a problem. Both of which happened!

On our 43' DCFB with much bigger engines than our catamaran, a predominance of 120 volt appliances, our generator and motoring to get anywhere, I do not see a value here for solar panels.

Just my humble opinion.

[Boatsb]

Don't even consider that the last 10% charging or a lead acid battery is extremely inefficient and becomes less than 10% efficient so the solar is usually not sufficient to maintain the battery bank properly and either the batteries will die young or you'll be running the generator.

[nautibake]

Propped systems use higher voltages from the panels and send it to a charge controller that puts it to the batteries.

I did a sailboat with a 12 volt house and inverter bank but brought 48 volts or so from the panels to the controller.

It was integrated to the inverter and control system with safety lockouts and solenoid to shut down unnecessary equipment should the battery run below a certain preset point.

So my first assumption was wrong, I assumed I would want a 24V panel to go to a 24V inverter bank.
Sounds like a great setup, almost fail-safe. What kind of solenoids do you use? Thanks for the insights...