There is a lot of info already around the forum so you can get a lot with the search tool.
Some quick points.
If you don't know your
power demand you need to tend to it now. You need to get into how much
power things take and how you plan to deal with it. You say 4 or 6
batteries but you really need to understand what happens when you have extra batteries or too few batteries. Both are bad situations. When you discharge you are only going down no more than 50% if you want to get the longest life. Then recharge them fully. But the tricky part is you need to get them fully recharged too. So if you have too many batteries you'll be
charging longer than you have to because as you get closer to 100% capacity charged you can't put as many amps into them without hurting them. So the last 10% is pretty slow. If you have too many batteries you won't get there very often except if plugged in or motoring all the time. Neither are great fun on a sailboat. Use as little power as you can and life is easier.
So you want all the batteries you need but you don't want any extras. That means you need to understand how you will use and charge your batteries before you begin. You have to size the system accordingly. You can't do it later without wasting a lot of time and
money. On a 32 foot
boat you might want to consider if the extra batteries are worth the space and if you really need them.
On our last 33 ft boat we had 6 Trojans where 2 were for starting. It lasted a long time but When we changed it out we went with a dedicated starting battery instead and used 2 group 4 AGM's. This was a great setup. The second boat has a dedicated starting battery and 4 Trojans. Both
boats have
solar and I can't say enough good about
solar panels. For one thing you can leave your boat unplugged most all the time and that alone saves you from all sorts of nasty things.
Inverters are expensive ways to use electricity. You throw away a fair amount converting it from DC to AC so it is best used carefully. For
computers never use an
inverter. Instead use a DC to DC auto adapter and save the double conversion penalty.
Our
current boat uses an
Ample Power regulator that takes the
solar panels and the alternator power inputs and regulates the output. If you use an external regulator you don't want an internally regulated alternator. One is enough. I think external regulation is easier to manage.
Battery monitors are exceptionally nice. The last boat has a Link 10
single bank
monitor. I never thought I needed to monitor the starting battery, but I had a switch that would combine the house bank to the starting battery in case the
engine didn't start. The
current boat has an
Ample Power monitor for two banks but it came that way so I don't need to change it.
I placed the 4 Trojans into two banks and then combine the two banks to one house bank. Flood batteries can get one bad cell and that one cell will trick the charging system into trashing the whole bank. If that happens you can catch it soon (you hope) and switch one bank off and not lose the whole mess. It's one of the many short comings of flood batteries. You must be religious about watch the
water levels. The
water level tells you when things are not all happy. If you need a lot of water added it means something is wrong. If you wait until you need 2 gallons then you are pretty much toast. You have to look to know. AGM's have none of these problems plus have lower internal Resistance and can be charged quicker with less power input. The only problem with AGM's is installing them in a boat regulated for flood batteries.
It's why I used to have Trojans, then got rid of them for AGM's and now have Trojans again. My regulation won't handle AGM's and I don't want to switch it out to do it just yet. The last owner installed the regulator plus when I got the boat it had a brand new identical regulator as a spare. Since you are
buying brand new they all should support either.
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