Yamaha Alternator

[Paul R Touchette]

I have a two battery w/switch Seafarer 228 w/300 Yamaha. I am a new owner.
Would appreciate e clarification on Yamaha alternator charging:
1) If I select battery 1 to run, does the alternator charge only battery 1 while running or does it also charge #2 ?
2) If I select battery 2 to run, does the alternator charge only battery 2 or does it it also charge # 1 ?
3) If I select "BOTH" to run, what happens ?
Thanks.

 

[DennisG01]

If you have the optional, "aux charging wire", that most Yamahas have... then both batteries will always be charged, regardless of the switch position. If not, then which battery is being charged is dependent on the battery switch.

 

[seasick]

Instead of tracing wires, you call tell by measuring the voltage at each battery under all the different scenarios. For example, run one motor at a time and see what the voltages are at all the batteries. It will be obvious if a battery is being charged, it's voltage will be higher than 13 volts. Try Battery 1, Both, battery2 for one motor then shut that motor and start the other and do the measurements again. Remember not to move any battery switches to or past OFF while any motors are running.That can harm the charging circuitry

 

[Sdfish]

Agree with above comments, also it is not recommended to run the switch on both, it would eliminate the redundancy of the 2nd battery. Only use both if one battery cannot start the motor.
I installed an ACR on my boat to manage charging. Blues Seas has a great detailed website with tons of information on it. Very easy install as well.

 

[Fishtales]

Agree with all input as well. One thing to watch is if you set the switch to both, the system will over time try to match both banks from a voltage level. You can end up draining the good battery/bank in that scenario.

 

[Fishtales]

One last thing is GW recommends a starting batter versus a dual purpose or deep cycle battery.