I have a 48 V battery bank consisting of 8 X 6V deep cycle golf cart batteries in series for an electric motor to drive the boat, and 12V battery bank consisting 4 X 6V in series and parallel deep cycle golf cart batteries for lights and instruments. Each battery is 225 amp hours. What solar panels and charger would you recommend and is it possible to use one set of panels and one controller for both the 48V and 12V bank, or do I need two independent panel systems.
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Solar panels and controller for 48V and 12V systems on sailboat
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That requires 2 separate systems. And a whole bunch of panels to charge the 48V system.Powerfab top of pole PV mount (2)  Listeroid 6/1 w/st5 gen head  XW6048 inverter/chgr  Iota 48V/15A charger  Morningstar 60A MPPT  48V, 800A NiFe Battery (in series) 15, Evergreen 205w "12V" PV array on pole  Midnight ePanel  Grundfos 10 SO59 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run  Runs off PV 
 Midnight Classic 200  10, Evergreen 200w in a 160VOC array 
 VEC1093 12V Charger  Maha C401 aa/aaa Charger  SureSine  Sunsaver MPPT 15A
solar: http://tinyurl.com/LMRSolar
gen: http://tinyurl.com/LMRLister 
Be aware that some MPPT controllers have a common negative between the panel and battery. Others are switched. That would cause big problems.Comment

Originally posted by PNPmacnab View PostBe aware that some MPPT controllers have a common negative between the panel and battery. Others are switched. That would cause big problems.Comment

If you have one controller common positive and the other common negative, it will short out the switching. Using two with common negative, it is highly likely that they sense current on the negative side and the two shunts would be in parallel and not read current correctly. It is probably unlikely that a sailboat would have enough panels making that matter much. Most controllers have no idea what is going into a battery anyway. There are devices that will charge a 12V battery from a 48V bank.Comment

Some amount of 48v can be converted into a reasonable amount of 12v for the 12v needs.
As was hinted above, best to do some math for that 48 volt propulsion idea with solar panels...panels may need help of onboard generator to charge batteries or maybe chance it from a full charge to empty batteries from a prior stationary full recharge.Comment

Amanzi,
I am watching this thread with great interest. I have been kicking around the idea of a solar powered catamaran for a few years.Comment

The 'scale' of this task can vary widely from a 'small dingy' to a 'big yacht'...at some point there may be different possibilities of outcomes...guess that's where the math comes in...sorta like difference between a offgrid cabin vs offgrid palace...big difference...
A quick way to 'ball park' math is by knowing how much petrol/fuel the solar is needing to replace is very usefull...
I'm no math wiz or engineer, but...3412 Btu equals 1kWh...where 1 gallon #2 fuel oil is equal to 138.690 Btu (@75% efficiency) for a base line...gasoline and diesel are some different.
So...using those numbers, 1 gallon #2 equals near 41 kWh...check me out, please...Last edited by neweclipse; 05202019, 11:43 AM.Comment

Originally posted by neweclipse View PostThe 'scale' of this task can vary widely from a 'small dingy' to a 'big yacht'...at some point there may be different possibilities of outcomes...guess that's where the math comes in...sorta like difference between a offgrid cabin vs offgrid palace...big difference...2.2kw Suntech mono, Classic 200, NEW Trace SW4024Comment
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