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Old 03-16-2007, 10:20 PM
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Default Battery-ACR-Switch

Guys, I know this has been beat to Death but I think I might have a slightly different situation. I'll start by telling you what I have and how I would like it to work.

I have a 175 Rude for power with the 8Ga. wire coming off of this Battery to the Cockpit Fuse Block for Ass. feed. I have a Manual start 15 Horse kicker with Alternator and wires going to a second Battery. Right now they are not hooked together.

I want to hook an ACR between the 2 Batterys so they both charge off of the 15 Horse because this is the Motor that I use most of the Day trolling around 5 or 6 Hours normally.

Now as I see it, the 1-2-all-off Battery switch is for switching between Batteries to 1 Motor, but I think I need to switch between Motors so as not to get any backfeed to the Alternator on the Motor that is not running. Am I wrong, or is it ok not to have a break in this circuit from the battery that is being Charged via the ACR by the 15 Horse to the non-running Motor??? If there is no danger in backfeeding to the Alternator on an idle motor, I could just use the 1-2-all-off switch.

I have the Blue Sea Catalog showing all the m series switches but dont know which one will fit the bill.

I just got this Boat last Fall and am trying to clean up the wiring before Splash time. No switches at all now and he had both motors hooked to 1 Battery.

I hope this makes some kind of sense as I am not a very good splainer or Electrician.

Can you point me in the right direction?
Old 03-16-2007, 10:30 PM
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Default Re: Battery-ACR-Switch

I'm an amatuer when it comes to modern 12 volt system, so don't take my observations as gospel, but does the alternator off the 15hp have enough guts to do the job! The ACRs have undervoltage and overvoltage sensors that will prevent "backfeed" - I think
Old 03-17-2007, 03:23 AM
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Default Re: Battery-ACR-Switch

Battery Switch:

1 - Conected to Start Batt

2 - Connected to 2nd Batt, Accessories & Electronics, 15HP Motor

Common - Connected to 175HP Motor


Connected to Start Batt & 2nd Batt

All batt negatives (12V -):

Connected together


Batt switch is set to 1 for normal operation, OFF when not using boat

Either engine will charge "it's own" batt & the other batt (if necessary) thru the ACR

Starting batt for 175HP motor is isolated

Emergency Starting (of either motor) can be done by putting switch to ALL


Any item accidently left ON when boat is not in use (electronics, accessories, etc) will discharge batt 2

Replacing the switch with a Blue Seas Systems 5511e (dual circuit) will eliminate this issue. When the switch is turned OFF, everything is disconnected. Auto Bilge Pump (if equipped) should be connected directly to batt 2 on switch

Old 03-17-2007, 09:08 AM
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Default Re: Battery-ACR-Switch

This has both the ACR and the 5511e switch, BOE has a good price on it:

Old 03-17-2007, 10:43 AM
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Default Re: Battery-ACR-Switch

There is no reason for spending money on switches and combiners - and except for increasing capacity, there is no need to have two batteries. Just connect both batteries in parallel with both alternators feeding them.

The only reason you would use a combiner is if you have a dedicated house battery and you want to prevent the house loads from running down the starting battery. If you wanted to dedicate one of the two batteries for starting and the other for house loads then you could put both alternators on the start battery and use a Combiner100 to charge the house battery.

The advantage of a Combiner100 is it just doesn't put the two batteries in parallel when the engine is running. It waits for the starting battery to accept a charge and only delivers the excess capacity of the alternator(s) to the house battery as that capacity becomes available. This prevents overloading an alternator that was never designed for house battery loads.

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