battery isolator

[dlp123]

have a 1991 19 foot galaxie powere by a 4.3 omc that iam trying to hook up another battery through a isolator would anyone know what wire to hook up to my alt because there is 2 of them and i figured out how to wire the second battery but my cranking battery charges through the starter i believe any help would be grateful or a diagram would be great thanks.

 

[bruceb58]

Re: battery isolator

Do your self a big favor and go with an ACR instead of the isolator. You will never fully charge your battery because of the diode voltage drop through the isolator. Then you don't need to worry about disconnecting any wires off your alternator.

if you do insist on using the isolator, the orange wire that goes to the starter is the one you connect to the input of the isolator. I am very surprised you only have 2 wires coming off your alternator. Typically there would be 3 or 4.

 

[dlp123]

Re: battery isolator

now that i got to looking there is 3 wires. Im wiring in some extra lights and i didnt want them on my cranking battery all in all ill have a fish finder radio bilge pump on the second battery i was wanting to do some night fishing this year

 

[Don S]

Re: battery isolator

First, disconnect the battery before you start messing with the wiring. Then follow the instructions below. It's from a Merc manual, but it's the same setup as you have on our OMC.

Couple of hints, disconnect the orange wire from the starter and the alternator. Tape back both end so they don't touch anything. No need to cut the wiring harness apart to remove the wire completely.
Make a new wire (instead of splicing) of the proper gauge to go from the alternator to the isolator.


View attachment Isolator hookup.pdf

 

[dlp123]

Re: battery isolator

thanks don i got the orange wire just taped off i ran one 10 gauge wire from back of alt to isolator. the isolator i bought wanted me to run another wire from the alt that come on when the key is in run position 12v source i guess thats the sense wire i checked both batteries while running there charging at 14.7 volts. it only seams to isolate the batteries when the key is off so i think all is good.

 

[UncleWillie]

Re: battery isolator

... it only seems to isolate the batteries when the key is off...

They are isolated all the time.
You will see the same voltage on each when the engine is running because they are both being charged to the same voltage.

 

[dlp123]

Re: battery isolator

thanks for the advice been awhile since i hooked up a isolator and that was on a truck so the boat wiring through me for alittle loop at first thanks everyone for the advice really helps knowing i can come to iboats and get parts and advice all in one shot.

 

[Don S]

Re: battery isolator

The isolator only isolates the batteries for charging. You still need to change the battery switch to decide which battery you want to use.

 

[dlp123]

Re: battery isolator

my boat never had a battery switch so i just found the main wire that runs my dash switches and hooked the aux battery to that.

 

[Don S]

Re: battery isolator

my boat never had a battery switch so i just found the main wire that runs my dash switches and hooked the aux battery to that.

It don't work like that.