Dual Battery selector positon when docking

[SHAGGY64]

Hello Folks I appreciate any insight. I have a 1991 V260 with 5.7 Mercruiser with dual batteries and onboard battery charger. What is the best way to leave boat docked with electrical docking cable connected? I left boat and selector was on 1 and connector came loose at pole. Needless to battery was drained. If I leave selector on off will both batteries charge? Or do they only charge when I leave on 1,2 or both. Thanks again

 

[CaptNCamille]

Re: Dual Battery selector positon when docking

On my boat, I shut both batteries off and leave the boat plugged in with the battery charger on. The charger will keep the batteries charged, and if the plug comes loose, the batteries don't drain. Not sure if that works with all boats, since it will probably depend on how your boat is wired.

 

[Chris1956]

Re: Dual Battery selector positon when docking

Shaggy, When the batt switch is on both, it appears to be a single large battery to the motor. It will charge both batteries, and the motor will use amperage from both batteries to start the motor. Other settings isolate one battery for those functions.

The way you are supposed to use dual batteries is to start on the odd battery on odd numbered days(ie Batt1 on July 1,3,5,7,9...), move the switch to both for running and charging, and then when you stop the boat, move the switch to the battery corresponding to the day, odd or even. if the battery you are using fails to start the motor, the other one should be fully charged from the day before's running, and will start the motor.

Most of us do not use a lot of power while out in our motorboats, so we leave it on both all the time, ans some of us shut the batteries off at the end of the day, in the slip or trailer.

 

[Mischief Managed]

Re: Dual Battery selector positon when docking

My dual-battery on-board charger is wired directly to my batteries. It bypasses the battery selector switch and keeps the two batteries isolated from each other. It does not matter what the switch is set to, the batteries get charged if shore power is plugged in, the shorepower main breaker is on and the charger breaker is turned on. I would be very surprised if yours was not wired the same way.

Since you have a mercruiser, you may have a Mercathode system to help prevent galvanic corrosion on the drive. It will not work if the batteries are switched off. Find out if you do have a Mercathode, and plan to have it powered at all times when the boat is in the water.