Join Date: Nov 2007
Location: SF Bay area
Thanked 7 Times in 6 Posts
Rep Power: 10
Thanks for the responses, folks. The way I've been planning on using this charger (which is indeed of the intelligent three-state variety, delivering 13.5-14.4 volts as necessary) is to top up batteries occasionally as I notice that its voltage has dropped too low. I've always attended closely to the process as I've never been quite sure what to expect. Prior to April of this year, the batteries were alternator-charged but then I swapped in an alternatorless (and pull-start) motor while the old one was under repair.
The boat's wiring is as follows: cables from the two batteries run to a Perko battery selector and thence to a pair of terminals in the engine compartment. What I'd really like to do is hook directly (and temporarily) to the terminals in the outboard engine compartment or, failing that, to run battery cables out of that compartment to someplace free from potential gas buildup (unlikely due to the enormous hole in the transom that the motor sits in) and not fire-prone. In my ignorance of such things, my concern there was that running a charge through the switch or other boat circuitry might be hazardous to that circuitry. The instructions were detailed on how to avoid the risk of spark using leads (basically, establish the final connections as far from the battery as possible).
What I've learned from your replies is twofold:
1) Not a problem to charge onboard if attended and for short periods of time (like a couple of hours).
2) My batteries should be inside boxes.
New questions that have been raised are somewhat more theoretical. I've seen wiring diagrams of, and mikehoyt mentioned, circuit hooked up to one terminal of a voltage source, and thence to ground. I was under the impression that current only flows in closed circuits, so what gives? On the practical side, when charging a battery, what's the difference between clipping on to both terminals, or to just one terminal?