Upgrade my current system

What is the voltage of your batteries and battery bank (i.e., 12 volt batteries and 12 volt battery bank)?

Assuming 12 volt batteries and 12 volt battery bank--You have a 12 volt @ 600 AH battery bank. If you are planning on living 100% from solar power with genset for just bad weather backup/high power needs for tool use, our off grid rule of thumb is ~5% to 13% charging for your battery bank. Lead Acid batteries have a minimum charging current for proper chemical reactions during charging and to keep up with self discharge. AGM batteries are better suited for 5% rate of charge (more charge efficient, lower self discharge)--10% is the typical recommendation for off grid living in a cabin/home--But for RV+Boats, this may be a larger array than you can fit on your place (not a lot off roof/deck space). So, the math would look like this.

• 14.4 volts charging * 600 AH * 1/0.77 panel+controller drating * 0.05 rate of charge = 561 Watt array minimum
  
• 14.4 volts charging * 600 AH * 1/0.77 panel+controller drating * 0.10 rate of charge = 1,122 Watt array nominal
  
• 14.4 volts charging * 600 AH * 1/0.77 panel+controller drating * 0.13 rate of charge = 1,459 Watt array "cost effective" maximum
  

Depending on your boat--You probably would have a hard time to fit more than ~561 Watt of solar panels.... Let alone trying to get >1,000 Watts.

In the above, you see that we have a recommended solar array based solely on the size (AH*Voltage) of your battery bank. Which now begs the question is your battery bank "appropriately" designed for your needs. For Lead Acid batteries, we typically size the battery bank for 1-3x your daily load with ~2x daily load as an "optimum" battery bank (cost/functionally a good match to loads/needs). And since we suggest you avoid going below 50% state of charge very often, that ends up with 2x daily load 2x for 50% maximum discharge or ~4x daily load as recommended battery bank size for an off grid cabin.

But for boats, many folks seem to put a relatively large battery bank in to support many days without genset power (quiet time at anchor, bad weather during sailing cruse). But, as you can see, this "forces" a larger solar array--But you have limited space for solar--Which may tend to force you to use the genset/fuel more than you want.

Anyway--My first guesses as to what your needs may be.

-Bill

OK--So the bank estimate I made seems to be accurate (600 AH @ 12 volt battery bank).

A "suit case" type genset (Honda eu2000i or eu1000i) can be pretty nice (small, quiet, efficient, reliable)--However, a small solar array (or even a small genset) is not going to make much of a dent on the battery bank state of charge...

Do you have an estimate of how much Amp*Hours you want to replace in the battery bank with solar and/or a "smaller" genset?

For example, say you use 1/4 of the 600 AH per day (or night)--~125 AH per day. If you have a 45 Amp battery charger on a Honda eu2000i:

• 125 AH / 45 Amps = 2.8 hours of run time minimum (realistically, if going for >90% state of charge, + few hours of taper/Absorb charging).
• and use ~1/2=3/4 a gallon of fuel per day (really rough guess)
  

And if you want to replace that full amount with a solar array with 5 hours of day of sun--that is a good amount on a boat?

• 125 AH / 5 hours = 25 Amp charge current
• 25 amps * 14.4 volts charging * 1/0.77 panel+controller derating = 468 Watt array to "break even" with 5 hours of sun per day

Of course, I have no idea of how much energy (or Amp*Hours) you actually use in a day--And "any solar" power can help--But you need substantial amount of solar to really help extend your "quiet time" on the boat.

"Deficit" charging on a lead acid battery bank is really tough on the batteries themselves (not replacing the AH used every few days--But charging to 90% one day then 80% the next day, 70% the third day, etc.). Cost of a "early death" battery bank vs more money for solar/fuel to keep the batteries "happy" is part of the ownership cost equation.

-Bill