using a battery isolator or parrelel bat's??

Hello,

I would like to hook up an isolator in my 2006 nitro 929CDX with a 99' 225HP Mercury Optimax DFI on the back to seperate the starting battery from the house bank batt but before i do so... does anyone know if this will work with the Alternator i have? it is a 60amp and in theory should be fine but my concerns are... i know the opti uses alot of the juice that is produced by the alternator during operation, will it provide enough to charge both batteries? might be a stupid question.. also... there is a sensor built in to the alt that decides how much to send to the batterries, will this work if i connect it to an isolator? and if it is ok to do this what gauge wire should be used as the wire coming out the back of the alternator only looks like its about 10 or 12 gauge and in my research would not be rated for 60amps... ??

Re: using a battery isolator or parrelel bat's??

The alternator will have a voltage regulator built in that will allow the alternator to put out between 13.8 and 14.8 volts for battery charging. The battery isolator will drop about .7 volts to foward bias the diodes in the isolator so will have about 13.1 to 14.1 volts for charging. Most alternators in cars with 100 amp alternator still use 10 guage wire. While this usually is rated at 30 amps you will find with wires long enough to reach the isolator or the battery that there will be enough voltage drop along the wire to limit the current to about 30 amps. Also at 30 amp charge rate the battery voltage will build up quickly and reduce the current it accepts to less than 30 amps in a very short time.

I know nothing about your outboard but if it rated at 60 amps then it very close to the 65 amps My I/O alternator puts out. I charge a starting and deep cycle with it. It uses a 10 guage wire to the asolator then on to each battery. The one difference is my alternator has a external voltage regulator and it senses the battery voltage not the alternator output so the .7 volt drop in the isolator does not affect the battery charging voltage. Mine senses the Starting battery voltage. This system has worked very well for me but I do not have a trolling motor or a big house load. All I have is the normal Starting battery that runs everything the boat came with and a deep cycle that runs all the add on electronics and accessory plugs.

Even with a 60 amp alternator it will still take hours to charge a 50 percent discharged deep cycle as the battery it self will determine how much charge it will take. As it charges up the current will be reduced all the way to zero by the time it is fully charged. It will do the bulk charge before to long then the completion of the charge will take a long time.