Some Quick Basics of Boat Batteries & Chargers

I’ll write a detailed series of articles on this at some point but until then, here are some brief pointers you can discuss with your boat electrician to keep the work tidy and truly correct:
* Bond everything metal (assuming a glass boat) to eventually a zinc, with clean connections. The majority of faults are on ground, rather than hot sides.
* An isolation transformer just inside shore power will do your boat’s electrolysis wonders.
* While AGMs are terrific for cranking amps, don’t leak or need filling, are vibration proof and can be mounted on edge, they are highly sensitive to low voltage and thus do not make good house batteries.
* A good gel cell can be brought down very low 500 times without damage but can not deliver or receive high amps without damage, so they’re ideal house batteries but will die quickly as starters.
* Gel and AGMs take different charging regimens, so the most efficient method is to have a separate charger for each. Obviously, this is not a good solution for budgets but it’s awesome and pays many times over, in the long run. I’m still running my two 8D gels for my house bank, installed in 1994.
* A good 3 or even 5 stage charger isn’t expensive and really worth its weight in gold – Check out the capabilities and doublecheck with the wholesale battery salesperson (Make sure you’re talking to a senior person!).
* Buy from a battery wholeseller and take time to ask questions about quality – There’s a ton of different purposes and you’ll find vast differences in amp-hours, life-cycles and cost. An AGM I commonly install is Trojan – They’re terrific value and come with a 5 year guarantee. Whatever you do, don’t buy “boat” batteries – They’re just marked-up and usually the cheapest in their class.
* Proper busses work wonders – Think the system through and leave 50% capacity. You’ll probably use half of that and be glad for it.
* I label every end, 8″ from the end, of every wire and match my busses + & – side by side, with labels in between, in the same order as the switch panel.
* I also leave workman’s loops (loose) so I can later pull wire. I know I differ from tradition here but no one’s ever had a complaint and I’ve had lots of compliments when customers later run wires or replace equipment.
I’d also check to see all ends are sealed in exposed areas and tell the boat electrician you’re going to look for proper sealed terminals everywhere. If you bring these points up, I’m sure you’ll be taken seriously.
One last thing: Nigel Calder’s Boat Electrician’s Handbook is IT! Buy it and you’ll understand everything. It’s written very clearly and has great diagrams and pictures. Best wishes!