Total boat electrical refit - looking for advice

[ShoestringMariner]

you never mentioned how you will charge these batteries. on a old mopar you could run a 10ga wire fused on BOTH ends 50amp fuse and go alt <> batt+.
dunno how that applies to you.
myself im gonna use a solar controller and panel to recharge.
there are wire size charts online. like your trollingmotor called for 8ga, because its going to use 30amps or whatever the spec is.
you can calculate all these things for the loads you will run - radio, troller, lights, etc.

I’m using a Noco genesis onboard dual bank charger for the 2 trolling motor batteries.
The starter battery will be charged by the alternator And I will likely hook that one up to A small solar panel while I am away to keep the battery topped in case the auto bilge pump cycles a few times. The bilge pump will be the only thing that does not go through the kill switch.

The reason I’m considering using this “mini add a battery“ switch system is because I don’t have shore power at the dock. So my electric charger is only used when I bring the boat home for early/late season boating elsewhere. During the summer season at my trailer, I’m hoping that the motor alternator can help keep both the motor battery level and the house battery level up when running. There are also entire weekends where I like to get out camping off the grid. I have to rely on whatever charge I brought with me or alternator power when running.

In any case, this system has a relay that allows the engine to charge both batteries but when the engine is off only the house battery is drawn off of by electronics etc. I know I can do this with a few disconnect switches in the circuit but this will allow a lot less for fooling around or forgetting switches on/off.

here’s a link to the video. https://www.bluesea.com/resources/533/Add-A-Battery_Video

 

[dingbat]

Batt 1 and 2 are approx 10’ apart. Those are the two I was considering pairing with the mini add a battery switch kit.
What size cable would you recommend at that length?

Evinrude manual
40-300 HP outboard
1- 10 ft. - 4 AWG
11- 15 ft. - 2 AWG
16- 20 ft. - 1 AWG

 

[ShoestringMariner]

Waaaaaait a second… it does not appear like I can switch it like a 1+2 system meaning I can’t use two batteries connected together to start the motor should the motor battery be drained from hard starting…. I can only charge both batteries. But draw from only one in an emergency start situation.

So I’m back to adding a couple of One, two, 1+2, off switches.

 

[dingbat]

So I’m back to adding a couple of One, two, 1+2, off switches.

Or an Off/On/Both switch like I use

 

[Scott Danforth]

Thanks, if I’m not mistaken, those are some hefty cables. I’m running a 50/60/70 hp series OMC triple. Having the third batt connected will be out of the question then as it is approx 18-20 cable feet from each other.

Batt 1 and 2 are approx 10’ apart. Those are the two I was considering pairing with the mini add a battery switch kit.
What size cable would you recommend at that length?

10 feet cable run, so 20 feet total? or 10 feet apart and 15 foot cable run or 30 feet total.

measure the total path the cable will be installed. multiply by two. that is total cable run.

with your 70hp OMG, and assuming 25 foot total run, I would be comfortable with 2 gauge

 

[Scott Danforth]

Waaaaaait a second… it does not appear like I can switch it like a 1+2 system meaning I can’t use two batteries connected together to start the motor should the motor battery be drained from hard starting…. I can only charge both batteries. But draw from only one in an emergency start situation.

So I’m back to adding a couple of One, two, 1+2, off switches.

why not. thats how the battery switches work. they draw and charge thru the switch

 

[ShoestringMariner]

why not. thats how the battery switches work. they draw and charge thru the switch

Thanks. Glad you mentioned this. I went back and looked at a different video. I was under the impression that it connects both batteries only during charging. I was not aware that it could be used to connect both for starting in the event of a discharged starter battery. Exactly what I was after

 

[ShoestringMariner]

10 feet cable run, so 20 feet total? or 10 feet apart and 15 foot cable run or 30 feet total.

measure the total path the cable will be installed. multiply by two. that is total cable run.

with your 70hp OMG, and assuming 25 foot total run, I would be comfortable with 2 gauge

10 feet between batteries. So 10 feet of positive, 10 feet of negative = 20’

Probably best to say 25 feet to be certain.

I was thinking 4 gauge, but slightly heavier won’t make too much of a difference to the pocket book

Thanks for your help.
Electrical is not my forte