Charging 2 Batteries

U

USMC-Korea-1951

Recruit
Joined
Jul 31, 2009
Messages
1
I have a 17' 1985 Chris Craft, I/O, 120 HP Mercrusier. A 12V battery for the boat electric. A battery for the trolling moter in the front, 55 lbs. thrust. Is it OK to charge both batteries connected in parallel from the boats 65 amp. altenator? Is 10 guage wire ok? Or do I need a $200 issolator & switch.

Thanks, Tom
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,762
Re: Charging 2 Batteries

If your batteries are connected in parallel, the connection between the two batteries must use cables that are the same size or larger than the battery cables going to the engine. Two batteries in parallel look like one giant battery as far as the alternator is concerned. Likewise, when starting the engine, the high current draw demands larger cables. As for the switch, isolator or ACR, its a personal preference. With none of these devices, a bad battery can suck the good battery down until the two are equal. A switch, isolator or ACR prevents that from happening.
 
J

john from md

Commander
Joined
Apr 13, 2008
Messages
2,184
Re: Charging 2 Batteries

You need to get a battery selector switch so that you can control what happens to your juice. If you just wire them in parallel, like Silvertip said, a bad battery can ruin a good one.

John
 
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