48V system on a sailboat

[mainsailman]

We are using three banks of 6v 215ah batteries for an electric engine conversion. I am about to start installing the solar system. What is the best way to charge a 48v bank? 12v panels? If so, do i wire them to 48v? If I have 4 12v 200ah panels wired to 48v, do I only get 200 watts? Or does it multiply unlike the bank? I have a ton of questions, so please bear with me.

[Sunking]

Last thing you want to use is 12 volt battery panels, they cost 2 to 5 times more than Grid Tied panels. Depending on the MPPT Controller you use you want to run panel voltage as high as possible like 90 to 500 volts. Higher the better. That allows you to wire panels in series and use very small wire with no expensive combiners and fuses. Low Voltage = Low Power & Poor Efficiency.

Having said that solar does not work well on a boat, especially a sail boat. You cannot keep the panels oriented and tilted at proper angles, nor can you keep the shade off them. Wind Turds work much better on boats. Use a large enough Wind Turd and not only will it charge your batteries, but push you along like a sail.

[NEOH]

We are using three banks of 6v 215ah batteries for an electric engine conversion. I am about to start installing the solar system. What is the best way to charge a 48v bank? 12v panels? If so, do i wire them to 48v? If I have 4 12v 200AH Panels wired to 48v, do I only get 200 watts? Or does it multiply unlike the bank? I have a ton of questions, so please bear with me.

Did you really mean to write "... 4 @ 12 volt 200 WATT Panels wired for 48 volts, do I only get 200 watts? ..."
The answer to your question is ...
No you do not get 200 watts, you get 800 Watts - you add the watts.
When Solar Panels are connected in series you add the volts 48 Volts = 4 panels x 12 volts
The same amps flows through all four panels at 16.67 Amps = 200 Watts / 12 Volts
800 Watts Total = 48 Volts Total x 16.67 Amps

[mainsailman]

OOPS, yes I meant 200 watt panels. As for the solar panels on a boat, most sailboat have them as well as a couple wind gen. It is a redundancy thing. Some days there are no winds while on others there are clouds with wind. I cannot go any higher than 48v grid. My banks are 48v. Anyone have any decent panels in mind for my grid? Or designs for a grid? Or other ideas. We also have an 8kw gen on board for emergency use. It is a large vessel. 36' long and a 12' wide beam.

[SunEagle]

Using an MPPT type charger will allow you to wire 4 "12v" panels in series to get the voltage needed to charge a 48v battery system.

The wattage of those panels will depend on the Ah rating of those batteries and I am still not exactly sure how you are wiring those 3 banks of 6v 215Ah to get a 48v system.

You need 8 of those 6v batteries wired in series to get a 48v system. "3 banks" would be 24 of those 6v batteries that could be wired to yield a 48v 645Ah system.

To properly charge that big of a system you will need at least 60amps of charging or close to 2900 watts of panels ( 60a x 48v = 2880w). That will require a few more than 4 panels.

So to help you find the right panel, exactly what is that battery system consist of and how is it wired?

[mainsailman]

You are correct. It is a bank of 8 6v 215ah batteries. They go to a switch that I can select which bank to use for the motor.

[SunEagle]

You are correct. It is a bank of 8 6v 215ah batteries. They go to a switch that I can select which bank to use for the motor.

To clarify. You have multiple banks of 8 batteries which each can be used independently to run the motor.

The problem I see is to charge all of the batteries you need to have them wired together to create one large bank being charged by a MPPT CC and solar panels sized for the Ah of the total bank.

Or you can have independent solar panels/charging systems that can generate about 20amps for each "bank" of 215Ah batteries.

[Sunking]

I cannot go any higher than 48v grid. My banks are 48v. Anyone have any decent panels in mind for my grid?.

You do not understand. Panel voltage and battery voltage are two different things. You can use a 600 volt panel to charge a 12 volt battery. Example here is a 600-volt Charge Controller made by Morningstar designed to run any battery voltage from 24 to 60 volts. . Most likely you will be using a 150 volt MPPT Charge Controller like these from Morningstar for any battery voltage from 8 to 72 volts. Solar panels do not know if they are connected to the grid or battery. They are dumb passive devices.

The trick is using a MPPT Charge Controller. That allows you to use inexpensive high voltage/power panels rather than expensive battery low voltage/power panels.

One problem, there is only one manufacturer that makes Marine grade Charge Controllers called Genasun. They only go up to 350 watts.

[ButchDeal]

One problem, there is only one manufacturer that makes Marine grade Charge Controllers called Genasun. They only go up to 350 watts.

Midnite solar makes some Marine versions of the Kidd at 30 amp

http://www.midnitesolar.com/productPhoto.php?product_ID=531&productCatName=Charge%20Controllers%20-%20KID&productCat_ID=43&sortOrder=2&act=p

[SunEagle]

Midnite solar makes some Marine versions of the Kidd at 30 amp
http://www.midnitesolar.com/productP...tOrder=2&act=p

That CC is probably a great idea for a 48V 300Ah battery with about 1400 watts of panels. But based on what the OP is stating it looks like a bigger system is needed for the larger battery.

[ButchDeal]

That CC is probably a great idea for a 48V 300Ah battery with about 1400 watts of panels. But based on what the OP is stating it looks like a bigger system is needed for the larger battery.

if he wants to use Marine grade CC then that is the largest one I know of. Luckily they can stack.
Otherwise non-marine grade...

[SunEagle]

if he wants to use Marine grade CC then that is the largest one I know of. Luckily they can stack.
Otherwise non-marine grade...

I agree. At least the Kidd can be stacked.

[Raul]

Victron energy does inverters,charge controlers specifically for marine use and they latest 250v 100A controler with a eficiency of 99% is not to shabby.

[Sunking]

Midnite solar makes some Marine versions of the Kidd at 30 amp
http://www.midnitesolar.com/productP...tOrder=2&act=p

Thanks, I will add that to my list. I was really just trying to make sure the OP understands Marine environments are tough on electrical systems. They have to deal with salt air, water, moisture,and petroleum.

[Sunking]

Otherwise non-marine grade...

That is a bad recipe, and not needed. He can use more than one controller.