Re: Battery charger question
Perhaps I'm a little to critical but I simply find it hard to understand why a battery switch is such a hard concept to get a grip on? You have only one SOURCE of power on a boat -- that being the engine alternator. If you have two engines you have two alternators but most of us have a single engine so that's where I will concentrate this discussion. The battery SUPPLIES power to the electrical system on the boat and it RECEIVES power (charged) be the engine alternator. Since you have two batteries and a battery swtich with BAT 1, BAT 2, BOTH and OFF positions these labels should be very definitive but apparently they are not so here goes again!!! Think of the switch as a "battery remover". When set to BAT 1 for example, BAT 2 for all practical purposes does not exist. When set to BAT 2, BAT 1 doesn't exist. When set to BOTH, both batteries appear as one giant battery. With the switch in the OFF position the electrical system for the engire boat is dead. No drain on either battery except for the bilge pump which should be directly wired to one of the batteries.
In the BAT 1 position ONLY battery one is running EVERYTHING on the boat leaving BAT 2 to go along for the ride. BAT 1 is the ONLY battery being CHARGED at this time.
When set to the BAT 2 position, the exact same scenario applies as BAT 1 except it applies to battery #2 and at this time battery #1 is going along for the ride.
Guess what happens when BOTH is selected? If you guessed anything other than BOTH batteries are powering EVERYTHING on the boat and BOTH are used to start the engine, then you need to have your wife or kids operate the switch. This switch setting places both batteries in parallel so to the electrical system the two batteries appear as one giant battery.
The wiring to a switch SHOULD have every accessory wired to the COM terminal on the switch as this is the SUPPLY route for power to those accessories. Nothing should be wired directly to the battery(ies) except for an automatic bilge pump or possibly an alarm system or some other device that needs to stay powered with the switch set to OFF.
Unless someone has done some creative wiring on the boat, the switch would be used as follows: If the switch is OFF and you are going to head out for a trip, set the switch to BAT 1 (typically designed the START battery) or BOTH. Start the engine and go boating. While under way BOTH BATTERIES will be charged or if you had left the switch on BAT 1, it would be charging. When you anchor for just a few minutes you don't have to panic about resetting the switch. If you do however, anchor for a longer period and will be using a high power radio, trolling motor or some other devices, switch to BAT 2 which is typically the house or accessory battery. This disconnects BAT 1 which prevents it from being discharged. When you are ready to go again, switch back to BOTH (or BAT 1) and head out. I recommend using the BOTH position since you would have run down BAT 2 so why not charge it again. To apply full alternator power to that battery, set the switch to BAT 2. So you see, the switch is like a water valve. It directs the flow of electricity in the boats electical system. If accessories have been directly wired to the house or starting battery, it makes no sense to have the switch in the first place since that defeats the versatility of the switch. Should BAT 1 take a dump (batteries do die you know), you can simply switch to BAT 2 and be on your way.
As for charging under way, the only viable solution is a properly wired switch or VSR/ACR. Solar panels are not an option. If AC power is available at the dock, then an on-board dual bank charger is the answer.
As for charging rates, trickle charging a battery is definitely NOT the best way to charge. It is the best way to "maintain" a fully charged battery. Batteries can and should be charged at higher rates, up to 20% of the rated AHr capacity of the battery. 100 AHr battery can be charged safely at 20 amps.
