Dual battery or booster pack?

[boscoe99]

No different than anything else that a motor maker specifies.

Ok to use non OEM products "IF" they meet specifications.

"IF" the Relion battery continues to meet Mercury's specifications then it "should" be OK.

 

[carlos515]

Ok, ordered a mini ACR rated at 65amp. My alternator is 65amp. Now would a 4awg cable to the ACR from the house battery be ok? Or should it be 2awg, like the starting battery is? I will draw maybe 30amp from the house battery.

 

[alldodge]

Your ALT will rarely output full amps, and you said it's 6 feet (double 12ft). So using double that and it's non-critical 6 awg will be plenty and 4 awg is even more

 

[carlos515]

Your ALT will rarely output full amps, and you said it's 6 feet (double 12ft). So using double that and it's non-critical 6 awg will be plenty and 4 awg is even more

Thank you.

 

[carlos515]

Now I have my main fuse panel primary wire going to my starter battery. I should be able to move this to the house battery? The ignition switch is my only uncertainty. Would the start circuit still work? The key switch goes to the starter solenoid, energizes it and the main start battery would power the starter.

 

[alldodge]

If it deals with the motor running it stays on the start Bat, as in key switch, gauges, starter, alternator, power trim, etc



If it's for any other stuff, this can go on the house Bat

 

[carlos515]

Thanks alldodge, I will double-check. I forgot about the throttle.

 

[carlos515]

Ok, I have drawn what I am thinking to do. All positive leads will have a fuse. I have an on-off switch that is going to be used for the main starting battery. The fuse panel under the helm will be moved to the house battery, as it is only for lights and bilge pump. My battery negative posts will be joined together.

 

[alldodge]

That will work
While not absolutely necessary if you add a Bat switch to connect House and Start Bat for use if Start Bat will not crank motor

 

[carlos515]

Ok, I have the batteries in. I am just waiting for a switch. I take it that a Harbour Freight on off battery disconnect would not be allowed in the boat?

 

[alldodge]

The HF switch should be no issue

 

[carlos515]

The HF switch should be no issue

Thanks, I have a Blue Sea m6011 switch coming. Now I can not find a schematic of the switch. If the switch is in the off position, does that mean both batteries are off? Or would I need a separate on/off switch for my house battery?

 

[alldodge]

My comment in post 29 was saying if you had a switch to connect both for emergency starts it would be helpful. Meaning a 3 post switch on/off/combine

My comment in post 31 was just saying the HF switch is ok to be used in a Marine environment

The 3 position switch is like this


This way if using 2 switches but this will not allow the ability to combine

 

[boscoe99]

As a side comment, I would say that if the starting battery failed to do its job of cranking the motor I would not parallel (combine) the two batteries without first seeing if the house battery alone would crank the motor on its own. Although perhaps not likely, it has been observed that paralleling a defective battery with a good battery has been known to render both batteries incapable of doing their functions.

If the house battery alone won't crank the motor then parallel the two batteries and hope that both together can get the motor started.

 

[carlos515]

Thanks everyone for your help and input. I have finished the dual battery project, along with my audio system upgrade.

 

[dingbat]

Although perhaps not likely, it has been observed that paralleling a defective battery with a good battery has been known to render both batteries incapable of doing their

Batteries when “combined” in parerell will equalizewill equalize

 

[boscoe99]

Batteries when “combined” in parerell will equalizewill equalize

Two good batteries, yes.

If one of the two is defective (not just low on charge) who knows what the outcome may be?

 

[alldodge]

If combined for a few seconds it will increase the current and also the better Bat will be able provide more voltage, which is normally enough to start a motor from weak Bat.

 

[boscoe99]

Without predicting what the failure mode of a dead battery will be in the future, I cannot hazard a guess as to what the results will be.

If in a lake right near the marina, go ahead and give it a try. If 50 miles offshore, on a stormy day, when it is getting dark, I would first try starting the motor on the house battery only and then parallel the two batteries once the motor is running, to see what happens. If the motor runs well, fine and good. If the motor starts to run poorly, or worse dies, I would personally run home on the one good battery.