Hi Dan. Yes, The trojans used for golf carts are regular lead/acid wet batteries. A step up is the AGM batteries which are still wet batteries but the acid is held in place within an Absorbed Glass Mat.
Mostly done so they don't spill.
The trojans have thicker lead plates so they can accept more cycles without the plates going to hell. Typically a golf cart type battery can be drained 80% max.
Bang for the buck makes them pretty economical. Because I need 14 batteries, the cost is going to be pretty high.
It seems that the 6 volt batteries have more available amps. I think that's due to the plate size as well.
A typical battery cell puts out 1-1/2 volts. Everything from an AA size battery to a big Semi-truck battery are like that.
The amps available are determined by the size of the cell.
A 12 volt battery has smaller cells than a comparable sized 6 volt battery.
I need to use 12 volt batteries because I'm using 4 motors and want to keep each motor and set of 3 batteries separate. This is just a safety issue so I can have a measure of redundancy available.
If a motor or controller or whatever blows, the breakdown only affects that one motor circuit.
I have the batteries inside the sub so as a last resort, I can jump a battery bank over to another circuit.
The individual banks of 3 batteries each are contained in a stainless box with a lid and gasket. Not "water proof" but sealed up pretty good.
Charging after a dive requires opening the lids and using a fan to vent the space during charging.
I'll need a gas detector in the sub too, to monitor any build-up during use of the sub as well as during charging. Batteries off-gas during use as well as during charging. The stainless boxes are a snug fit so the volume of space available inside is minimal, hoping to reduce the danger of an explosion.
The golf cart chargers I'm looking at charge at 36 volts/20 amps for the 110 volt model but a 220 volt charger will do the job a lot quicker. The chargers also have the circuits to adjust the charge rate automatically as the batteries reach full charge.
My worry there is that not all harbors have 220 available at the dock. My local harbors have 220 but not sure if other smaller harbors do. Maybe will need more than one charger.
I've seen some info on the li-ion batteries in the "automotive" size but they run $1200 each and are prone to exploding if the draw down gets too high. With the small space in a psub, that would be deadly!
Frank D.