Wire size for cranking battery and other wireing help.

[sooutlandis]

Hello everyone. Im getting ready to move my batteries to the front of my boat but im wondering what size wire people suggest, and is it actually necessary to use tinned wires. The batteries will be about 12' from the motor. Will 4awg be enough to start the engine at that distance? Its a older 25hp johnson. Also im going to add some inboard deck lights and a few other accesories. Do i need to have a grounding block or can I run wire from the battery to my switched breaker board? Any and all help is much apreciated.

Thank you

 

[huntinfool]

There are some wire calculators online that will tell you how much voltage drop a wire will have and how much load you're trying to carry over what distance.
My opinion is that might work, especially since it is just a cranking battery. However you may need to up the size.
As for the other part of your question, each light will need to be grounded. You can run a bigger wire to a grounding block and smaller wires from there to each light, or run wires all the way to the battery. As for your switched breaker board, who knows. Does it have a grounding block on it? Does it have a ground lug?
We will need a picture or a schematic of it before we can answer that part.

 

[sooutlandis]

Thank you for getting back to me. Here is a picture of the switches that I have. Probably have a am/fm stereo, lights, accessory plug, and a bilge pump.

 

[onthewater102]

#4 is plenty big - I've moved batteries in cars to the trunk and the kits designed for this purpose use #4 wire and the amperage draw of a car-starter is well beyond what would be needed to spin a small outboard motor.


As far as needing a grounding block - I don't understand your question - would you be grounding everything individually to the battery? In that case no, but it'll be a sloppy mess. You shouldn't go grounding to the hull the way you would a car-frame if that's what you were thinking to do. I would make sure you have a fuse in line with that switch panel too. Personally I used a grounding block to keep the battery connections to a minimum.

 

[earl60446]

Looks like your switch panel has connections for both the grd and pwr so good to go there. The wiring on it looks a bit light so keep it to things like fish finder, small bilge, couple lights, stereo as you mentioned. Provided a chart for you below on the starting circuit. I don't know how much a 25 hp johnson draws when starting. I think 4awg should handle your situation though.
Tim

 

[onthewater102]

The ground connections in his panel are for the lights built into the toggle switches not for the powered devices. He'll hook his accessories to the empty blade positions and still need to ground the accessory from there.

Great table! I've got to save that one.

 

[Nohasslekindaguy]

Your factory battery cables should be 5 to 6 feet long and are a #6 cable. If I was moving the battery farther than that, I would use at least a #4.

 

[onthewater102]

Cable size will depend on the motor - I've got a 55# Minn Kota Traxxis and it's got #8 wire, probably 5 or 6' long like you said...

 

[Nohasslekindaguy]

onthewater102 » Today, 14:35[/url]"]Cable size will depend on the motor - I've got a 55# Minn Kota Traxxis and it's got #8 wire, probably 5 or 6' long like you said...

I believe he is moving his starting battery for the outboard, not the trolling motor battery.

 

[onthewater102]

..oops I was flipping between posts and got myself mixed up between the two...


Looking at the USCG table #6 wire is adequate out to 20' allowing for a maximum of 10% voltage drop. At up to 10' the max drop should be 3%. Digital controls are most sensitive to variability in voltage, being an older motor there won't be any digital processing between the key switch and the solenoid activating the starter. Use the same gauge wire as was on the motor, #6 if that's what it is as you're only planning on being 12' away (even allowing an extra 6' for twists and turns to tuck it in nicely will not put you passed the 20' guidance. Your fish finder might loose power as you try to start the motor is all.

 

[lovedr79]

when I moved my battery to the front of my boat I bought a set of jumper cables, cut the clamps off and added connectors on the ends, and the bonus - I don't have two giant wires. plus going the jumper cable route it was cheaper than buying cable from lowes.

 

[onthewater102]

Awesome idea!

 

[sooutlandis]

Thank you everyone for the replies. I ended up buying #4 tinned wire. Havent tried to start the motor yet but im sure it will be fine.