Battery cable gauge

[bass or bass ?]

I'm installing a 1/2/both/off battery switch. I want to locate it next to my steering console and the length of run for the cables will be @ 22 feet. What gauge battery cable do I need to use for this length run?

 

[Grub54891]

Why so far from the battery's? And you have to know the amps you are drawing to calculate the wire size.

 

[Chris1956]

Well, some googling of an automotive wire size site, tells us that 150 amps (typical starter draw) at 20 feet requires a 2/0 gauge wire.

 

[JASinIL2006]

That's going to be a pricy run of wire, especially if you use tinned marine wire... 2/0 tinned wires seems to run north of $5US per foot.

 

[Grub54891]

Well, some googling of an automotive wire size site, tells us that 150 amps (typical starter draw) at 20 feet requires a 2/0 gauge wire.

20 feet. That's from the battery to the switch? If so you have to double that, as its 20 feet back to the motor. You may have to re-calculate.

 

[Prophammer]

that is a long run for battery cable, I would use only marine wire and make sure it is well protected from chaffing , 2/0 gauge should be plenty heavy enough unless you're running big caterpillar diesels or the likes of

 

[Scott Danforth]

Battery 1/2/off/both switches are rated to 400 amps. not knowing what you starter motor is drawing, however assuming 200 amps (BTW, in-rush current is much higher)

your voltage at your starter over the 44 feet of motor run (22 there and 22 back) would be only 9.25 volts with 2 gauge wire - 2.75 volt drop

if we assume 22 feet total (11 there and 11 back) your voltage drop is 1.4 volts or your battery voltage at the starter is only 10.6 volts

at 2/0 wiring, 22 feet is a 0.7 volt drop, 44 feet is 1.4 volt drop
at 4/0 wiring, 22 feet is just under a 0.5 volt drop, 44 feet is about 1 volt drop

generally I shoot for 1/2 volt or less voltage drop to compensate if you have a marginal battery so you never drop below drop-out voltage of the ignition/fuel system.

you are going to have to up-size your wiring to at least 4/0

this is why battery switches are at the batteries

 

[AShipShow]

I located mine under the rear seats so I don't have to get under my sundeck/engine cover just to access it... I was able to keep the wiring run down to about 10 total feet... I would recommend doing something like this... Make it easy to access for convenience, but as close to the battery/starter as possible.

 

[Grub54891]

Battery 1/2/off/both switches are rated to 400 amps. not knowing what you starter motor is drawing, however assuming 200 amps (BTW, in-rush current is much higher)

your voltage at your starter over the 44 feet of motor run (22 there and 22 back) would be only 9.25 volts with 2 gauge wire - 2.75 volt drop

if we assume 22 feet total (11 there and 11 back) your voltage drop is 1.4 volts or your battery voltage at the starter is only 10.6 volts

at 2/0 wiring, 22 feet is a 0.7 volt drop, 44 feet is 1.4 volt drop
at 4/0 wiring, 22 feet is just under a 0.5 volt drop, 44 feet is about 1 volt drop

generally I shoot for 1/2 volt or less voltage drop to compensate if you have a marginal battery so you never drop below drop-out voltage of the ignition/fuel system.

you are going to have to up-size your wiring to at least 4/0

this is why battery switches are at the batteries

Exactly. When I posted I didn't have the calculations figured out yet. Post #5.

 

[bass or bass ?]

Thanks everyone. I've decided to just install the switch near the batteries instead of at the console. I had wanted the convenience of having the switch within reach but it is apparent that this idea simply will not work.

 

[Scott Danforth]

Thanks everyone. I've decided to just install the switch near the batteries instead of at the console. I had wanted the convenience of having the switch within reach but it is apparent that this idea simply will not work.

Its not that it wont work....... Its that it will be about 10x more expensive than you anticipated

 

[H20Rat]

You can still do it without spending a huge fortune, just take the remote to the console and leave the battery cables where they belong! Remote battery switches aren't that expensive in the grand total of 'boating'.

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