1989 470, 3.7L - dual battery install - confirm

[nwboater45]

I have a 1989 MCM 470, 3.7L that I just installed dual batteries on with a Perko switch. The switch selection is 1, 2, All. The reason I am not posting in the electrical forum is that I want to confirm the charging system in my boat. I also still have the stator and not an alt.

So according to service manual #8 there is an orange wire that goes from the voltage regulator to the starter post. Is the wire that is sending the charge back to the batteries? Or am I not reading that correctly?

The way I set up the dual batteries is (one on each side of the boat), batt 1 & 2 ground wires are going to the engine block in separate locations. Batt one poss is going to the perko post 1 and batt two is going to the perko post two. The starter wire is going to the common post. So basically the same in the attached diagram. Batt one is the starter batt and batt two will be for accessories.

So the question I have is, so no matter what battery I have it switched to that battery will be the one charging, correct? Is there ever really a reason to have the switch selected to all? I read one thread in here that might be bad for the system.

 

[achris]

Re: 1989 470, 3.7L - dual battery install - confirm

Looks exactly like the system I have on my boat..

As for which battery to switch to.... I use 2 of the same batteries, N70ZZ, and run with the switch in the ALL position virtually all the time. The one stipulation I would put on that, replace both batteries at the same time. Batteries change their internal resistance as they age. When you put 2 batteries with different internal resistances in parallel, you set up an unequal circuit (there's a word for it and I can't remember it :facepalm, and they will drain each other.

I also turn the switch to one or the other for overnight stops. That way I KNOW I have a battery good for a start in the morning. I used to turn the battery switch to OFF when I got home, but I recently bought a small 'intelligent' charger. I now leave the battery switch in the ALL position and hook the charger up as soon as I get home.... Now my batteries will last longer, and I know they are 'hot to trot' when I'm in 'fishing mode'....

Chris.......

Oh, all your other assumptions are correct... The orange wire from the regulator to the starter carries charge current there, then that's connected to the batteries (via your switch)...

One more thing... NEVER NEVER NEVER turn the battery switch to OFF when the engine is running, EVER.... Or even run the selector though OFF as you go from '1' to '2'. If you want to go from '1' to '2', go through ALL. Those 2 small wires that come from the battery switch, F1, F2... They are for people who might be in the habit of turning the switch to or through OFF. They disconnect the field windings from a standard alternator, thus instantly dropping the output to 0. If you don't disconnect the field winding, and you disconnect the batteries from a running alternator (switch to OFF) then the alternator has no reference and the voltage will spike as high as the alternator can make it, high enough to blow the back end out of instruments, radios, GPSs... anything that doesn't like high voltage... Don't ask how I know :facepalm:

 

[alldodge]

Re: 1989 470, 3.7L - dual battery install - confirm

Agree with the way your doing it, and achris.
Mine is setup using an isolator connected to the ALT and a two bank battery charger, both charge both banks when plugged in or running. My start battery is used just for starting and is not electrically connected to the other except through the isolator. The accessory battery can be pulled down to nothing and will not effect the start battery.

 

[nwboater45]

Re: 1989 470, 3.7L - dual battery install - confirm

Thanks guys for the information. Electrical is not my game and I didn't want to fry anything.

achris, my off switch is all the way to the right so it goes 1-all-2-off. I am not an overnighter so when I store the boat the switch will go to off. I will probably switch it to 1 when I am making a run and then 2 while I am fishing.

Alldodge, I am planning on doing the alternate conversion this winter or next spring. I did read something on using the isolator when using an alternator so I am sure I will have more questions during the conversion.

Thanks all and thanks iboats.com

 

[achris]

Re: 1989 470, 3.7L - dual battery install - confirm

...I did read something on using the isolator when using an alternator so I am sure I will have more questions during the

If you're planning on using the isolator switch F1 & F2 connections, then you need a 3 wire alternator, not a 1 wire.

Chris....

 

[nwboater45]

Re: 1989 470, 3.7L - dual battery install - confirm

Chris, thanks for the heads up on that one.

 

[a1nowell]

Re: 1989 470, 3.7L - dual battery install - confirm

nwboater45,
I made the conversion 4 years ago and have the same battery selector as described above. I got my 3 wire conversion kit from
Breezeworks it bolted right up with no problems.

Larry