Cable Size / Voltage Drop Calculator

[nigelmercier]

I'm on my boat at the moment, so internet access is a bit limited.

I need a cable size calculator for 10m (there and back 20m) @ 10A. I've tried three different calculators, with widely different results.

Can anyone point me to the one that is recommended please?

 

[prv]

Here's a screenshot from my own cable-sizing spreadsheet:

Pick the size you like based on acceptable drop

(The left column is standard cable sizes, the one headed % is the percentage volt-drop. Labels are a bit cryptic and formatting basic as it was never intended for general use )

This was with a voltage of 12v - I can run it again with another figure if you think your batteries might actually be higher.

Pete

 

[Melleman]

http://www.calculator.net/voltage-drop-calculator.html

 

[VicS]

I'm on my boat at the moment, so internet access is a bit limited.

I need a cable size calculator for 10m (there and back 20m) @ 10A. I've tried three different calculators, with widely different results.

Can anyone point me to the one that is recommended please?

I often refer to this one on Engineering Toolbox ( unfortunately being 'merican its in feet and AWG)

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

but now prefer to do my own calculations from first principles using the table in the link on that page namely http://www.engineeringtoolbox.com/wire-gauges-d_419.html which does give the cross sectional area in mm² and the resistance in ohms /1000m

I am sure the calculation method will appeal to you

 

[nigelmercier]

Here's a screenshot from my own cable-sizing spreadsheet ...

That looks clever (so 10mm² minimum, 16mm² preferred).

Any chance of a copy?

Thanks also to Vic, although I hate using AWG. Feet I can cope with

 

[Hydrozoan]

I'm on my boat at the moment, so internet access is a bit limited.

I need a cable size calculator for 10m (there and back 20m) @ 10A. I've tried three different calculators, with widely different results.

Can anyone point me to the one that is recommended please?

Mmm. I suspect you'll now end up with more than three to reconcile. Vic's first principles approach might perhaps cut the Gordian knot.

 

[pvb]

I do rough volt drop calculations using the "treble 1 twenty" formula. 1A x 1 metre x 1 sq mm = 20mV drop.

Increase the volt drop for bigger current or bigger distance; decrease the drop for bigger cable size.

So, 10A x 1 metre x 1 sq mm = 200mV drop
10A x 20 metres x 1 sq mm = 4000mV drop
10A x 20 metres x 10 sq mm = 400mV drop
etc, etc

Quick and easy, don't even usually need a calculator (although there's one on your phone if you do).

 

[prv]

Any chance of a copy?

Do you use Numbers?

It's not hard to build your own, given a list of the resistance-per-metre of the different sized cables.

Pete

 

[nigelmercier]

It's not hard to build your own, given a list of the resistance-per-metre of the different sized cables.

Yes, but you made a working wheel

 

[sparkie]

Interestingly Nigel you've got the same problem with the cable as you have with your sink drain............. Smaller and longer the pipe/cable, greater the losses... Simples! Cheers S.

 

[Mistroma]

Nigel, I put a trivial XLS together years ago and have used it for these calculations.

i.e. 18.1/((volts*1000/amps)/metres
It is based on: CSA mm2 = 18.1/((volt drop [volts]*1000/current [amps])/length [metres])


You can see the calc. =18.1/((C7*1000/C3)/C2) in pic. below

View attachment 48623

Very simple with all cells locked apart from those in grey, allowing modification of cable run, current, supply voltage and required voltage drop.

I can pm a copy if it might be of some use though you could probably create in around the time it would take to let me know if it would be useful.

 

[prv]

Yes, but you made a working wheel

Only if you have a copy of Numbers to bolt it onto

Pete

 

[nigelmercier]

Only if you have a copy of Numbers to bolt it onto

Ah, Numbers with a capital "N".

I use Excel, but easy to Export from Numbers if you are feeling kind: https://discussions.apple.com/thread/6088119