Upgrading 24V to 36V wiring?

[96ranger492vs]

I'm really thinking of making the jump from 24V to 36V but am no electrician and want to know about wire size. I looked it up and according to Minnkota my 80# 24V motor has a higher amp draw than a 112# 36V motor will and recommends the same 60 amp breaker for both. In theory, should my existing wiring be ok for a 36V motor? All I would need to do is add a 3rd battery in the series and be good, right?

[John Jackson]

Correct. The voltage and wattage are higher but the amperage will be the same or lower. Breaker will be fine. Use 6 awg wire.

[96ranger492vs]

Correct. The voltage and wattage are higher but the amperage will be the same or lower. Breaker will be fine. Use 6 awg wire.

Is your recommendation of 6 awg wire just to get less of a voltage drop or would 8 awg be ok just to not set the boat on fire. I'm not too concerned with a voltage drop but am concerned with safety. I don't want the boat to catch on fire.

[John Jackson]

Voltage drop. 8 awg will work.

[96ranger492vs]

Voltage drop. 8 awg will work.

Thanks for the advice

[Jonestrollingmotor]

Depending on what you're putting it on and the length of wire on whether 6 or 8 is needed. Personally, if the wire run is over 30' (that's from the negative connection of battery 1 to the positive connection of battery 3 in the case of 36V) I would go with 6ga. Also, I would not use a 60A breaker on 8ga wire.
John

[96ranger492vs]

Depending on what you're putting it on and the length of wire on whether 6 or 8 is needed. Personally, if the wire run is over 30' (that's from the negative connection of battery 1 to the positive connection of battery 3 in the case of 36V) I would go with 6ga. Also, I would not use a 60A breaker on 8ga wire.
John

Why would you not want to use a 60 amp breaker with 8 awg? I'm trying to avoid tearing wiring out and installing new but also don't want to be unsafe. It will be on a 21' Ranger bass boat

[rockmike]

I'd add the battery and trolling motor and go fishing.

[Jonestrollingmotor]

Why would you not want to use a 60 amp breaker with 8 awg? I'm trying to avoid tearing wiring out and installing new but also don't want to be unsafe. It will be on a 21' Ranger bass boat

a 96 Ranger should have 6ga wire. Are you sure the wire is 8ga? To answer the question, 45' of 8ga wire is pushing it to carry 50A, let alone 60A. If you breaker it for 60A and the wire won't carry it, then the wire becomes the fuse and will burn before the breaker trips.
John

[Lou r Pitcher]

The Ampacity of a given wire size refers to its current carrying fire safety aspect and is unaffected by the length of the wiring.

For an electronic product such as a digital trolling motor, wiring voltage losses (not Ampacity) is the consideration necessary for selection of the correct wire size. A 5% max voltage loss is recommended by Minn Kota:
https://www.minnkotamotors.com/sites...le_9-11-14.pdf

[Jonestrollingmotor]

The Ampacity of a given wire size refers to its current carrying (fuse value) fire safety aspect and is unaffected by the length of the wiring.

Understood. If you have 45' of wire, isn't the resistance (especially in the smaller wire size) going to be more than it would be on say a 10' length. If amps is equal to voltage divided by resistance, and voltage is a constant, then wouldn't amps increase as resistance increases. I'm thinking outloud and after the day I've had, may be confusing myself.

[John Jackson]

V/R=A. The higher the resistance, the lower the amperage for a given voltage. But it does mean less voltage to run the motor.

[Jonestrollingmotor]

V/R=A. The higher the resistance, the lower the amperage for a given voltage. But it does mean less voltage to run the motor.

Understood, however in the instance of a trolling motor and wiring, the voltage will remain constant (or close, depending on voltage drop) at 12, 24, or 36, depending on the trolling motor. When you increase the length of the wire, the resistance rises until you go to larger wire. In simple math, when the dividend remains constant (V), you raise the divisor (R), then the quotient (A) will decrease. Since the trolling motor will try to pull it's rated amps, this will cause heat in the smaller wire. Lou made this statement "The Ampacity of a given wire size refers to its current carrying (fuse value) fire safety aspect and is unaffected by the length of the wiring." which I agree with the first part. What I'm trying to say is the length of wire does effect the current carrying capacity due to the resistance.

[96ranger492vs]

Thanks for all the advice guys. Like I said before, I'm no electrician and after looking at it I'm pretty sure it's 6 awg wire now I just need to find room for my 3rd battery.

[Lou r Pitcher]

A given wire size by the ampacity tables will be stated to have a fixed amount of current carrying ability.

The longer the wire becomes, yes, the higher becomes the wire's total resistance. And I can agree that if current remains the same, the watts (heat dissipated) becomes higher as the wire gets longer. But the heat generated by that higher resistance is dissipated over the increased distance of the wire. The wire at any location gets no hotter just because the wire is longer.

My commenting point is that if say a 5 foot wire can carry for fire safety exactly 10 amps and no more, then 50 feet or 500 feet of that same wire also can carry 10 amps and no more. Wire length has no effect on the ampacity (max safe current carrying capability) rating of a wire.

I think Mr Jones point may be that many devices whenever their supply voltages become reduced will actively draw increased current. An example is any regulated power supply. It is active compensating electronic circuits within these devices that will draw more current to make up for the losses of their supply voltage. These voltage losses can be a result of the increased wire resistance of using longer wires.

The capacity of the wire (ampacity) should never be exceeded and an included over-current device (breaker or fuse)is included in the wiring to assure that.

f amps is equal to voltage divided by resistance, and voltage is a constant, then wouldn't amps increase as resistance increases.

In a simple high resistive load circuit.....

Voltage is measured over the length of wire and is not at all constant....... If the wire length doubles, the resistance of the wire doubles and the voltage (loss over the length of wire) doubles .