Hey Bacchant, I too am in the process of rewiring and installing completely new battery banks, for which I have done considerable research
. You have not given a great deal of information about your proposed battery installation
. So, how many batteries and of what size? Separate house and starter banks? What kind of charger(s)?
I am planning to install a house bank of four 6-volt deep cycle batteries and a separate starter battery. This will be replacing a house bank of two Series-31 deep cycle batteries and a starter battery. The four 6-volt batteries represent a combined weight that is pushing over 260 pounds (123 Kilos), so appropriate placement is important from a balance perspective. I had thought of placing them in the bilge, but the space was too tight for easy maintenance
and I too had concerns about flooding. However, from a weight and balance perspective the bilge was ideal. So, you may want to consider the impact on your boat's balance if you relocate. I will be locating mine under a main-cabin settee, in a locker which is as low down and central to the boat
Lead-acid batteries can emit hydrogen gas when charging, but the quantities are small if you are using a proper charger
. If you are using an old-fashioned charger
that boils off the electrolyte, well, then things can be different. A small vent to the open cabin
in the upper corner of the battery compartment should be sufficient to safely disperse any gas discharged. I will be installing a ProNautic 12-40P charger which has sufficient capacity and smarts to keep my batteries going for a long time.
One important thing to consider: for lead-acid batteries the optimal orientation is transverse, across the beam of the boat. This does a better job of keeping the plates covered with electrolyte while heeling, as opposed to a longitudinal orientation along the fore-and-aft line of the boat. I did some rough calculations for the 6-volt batteries. On a longitudinal (fore-and-aft) orientation, the top corners of the lead plates get exposed starting at about 15 degrees of heel, presuming that the cells are all fully topped up. If they are not, then exposure occurs with even less heeling angle. On a transverse (across the beam) orientation, the tops of the plates do not get exposed until you reach about 35 degrees of heel, which no sailor willingly sustains. Exposure of the lead plates has implications for amount of charge available, as well as sulfation and battery longevity.
My starter battery, which is lighter and has infrequent loads with minimal charging activity will be located in its own box within the cockpit
locker/engine space. Regardless of position, all batteries will be well-secured so that they cannot shift or tip over. I learned that lesson very early in my sailing career.
I hope that this has provided some food
for thought. Good luck on the project