Acceptable DC voltage loss

[Austin68]

What does everyone on here consider a max acceptable voltage loss for your DC cables?

 

[Zil]

It is always recommended to have not more than 3% for critical circuits. When selecting cable awg, there is the cable voltage drop. Also each connection, crimp, and fuse contributes voltage drop. I use 1% on the charts when selecting the cable, knowing the other voltage drops will add to that percentage. I have to be careful using the marine voltage drop tables as ABYC has increased the standards leading to larger cable gauge requirements. Maybe necessary when out to sea and alone, as most boat fires can be traced to faulty electric stuff. But not as much in my camper or maybe your S&B.

 

[HRTKD]

As stated in the post above, 3%. I tend to put in larger wire than necessary so my voltage drop due to the wire is like less than 2%.

 

[timselectric]

3%
Same as everyone else.

 

[Zwy]

What does everyone on here consider a max acceptable voltage loss for your DC cables?

I like 3% for the calculator, then step up one size on the cable.

 

[MisterSandals]

What does everyone on here consider a max acceptable voltage loss for your DC cables?

Consider what the loss actually is, generated heat.

If you have 48V and 200A = 9600W
3% of this is 288W

That’s roughly 10x little soldering irons.

Do the math and calculate the loss/waste/heat with your setup.

 

[timselectric]

I always oversize my wiring. If I get hot, I can lay on it to cool down. lol

 

[Roswell Bob]

Consider what the loss actually is, generated heat.

If you have 48V and 200A = 9600W
3% of this is 288W

That’s roughly 10x little soldering irons.

Do the math and calculate the loss/waste/heat with your setup.

That translates to about 0.0072 ohms. ( I think) That is about 7' of #10 wire.
a 3/0 wire has about 62uohms/ft This translates to about 112' round trip for 3% losses. Check my math please. I am not a mathematician.

In any case the wire needs to be sized for FLA.

 

[Austin68]

That translates to about 0.0072 ohms. ( I think) That is about 7' of #10 wire.
a 3/0 wire has about 62uohms/ft This translates to about 112' round trip for 3% losses. Check my math please. I am not a mathematician.

In any case the wire needs to be sized for FLA.

I was looking at putting my array about 170 ft from my controller. But voltage would be high, around 412 voc and only 10 amps with 6awg wire

 

[rmaddy]

I was looking at putting my array about 170 ft from my controller. But voltage would be high, around 412 voc and only 10 amps with 6awg wire

At 412Voc and 10A you will have trivial voltage loss using 6AWG. You could probably use 12AWG at that voltage.

Do make sure you use high quality wire at that voltage. Most decent wire will be rated for 600V.

 

[timselectric]

I was looking at putting my array about 170 ft from my controller. But voltage would be high, around 412 voc and only 10 amps with 6awg wire

Need vmp

 

[Zil]

Bob. Dont over look connections crimps and fuses for additional voltage drop.

 

[Austin68]

Need vmp

344.7

 

[timselectric]

344.7

14 gauge would put you at 2.93% voltage drop.
But, I wouldn't recommend anything less than 10 awg.
344v
10a
170ft

 

[MisterSandals]

345V x 10A x .0293 loss = 101W loss when pulling 10A

 

[timselectric]

10 awg is 1.16% voltage drop.
Much better.
Less than 50w loss.

 

[MisterSandals]

Much better.
Less than 50w loss.

Just messing with numbers... 50W better for a year...

50W x 24 / 365 = 438kWh

438kWh x $.25/kWh = $109.50 savings per year (assuming constant 10A which is not likely)

 

[Austin68]

14 gauge would put you at 2.93% voltage drop.
But, I wouldn't recommend anything less than 10 awg.
344v
10a
170ft

I have some 6 gauge that i was going to use

 

[timselectric]

I have some 6 gauge that i was going to use

Even better
.46% voltage drop