# Help Please!! calculating cables losses any FREE DC power design tools

Discussion in 'General Electronics Chat' started by brendan, May 6, 2008.

1. ### brendan Thread Starter New Member

May 6, 2008
2
0

Can someone help me with learning some DC basics for solar design.

How do I calculate losses in 3-5mm wire power cables used in dc 14.2volt 6Amp(max) Wiring is from a nominal 12V dc solar power source, 5-10metres distance to battery storage, and from the storage approx 5-7metre the load.

So if you can help me with some free advice or teachings on
design and calculating basic dc circuits. want to learn the old school way with brain, pencil and paper working.

very happy to know where any great free, design tools or calculators suitable for simple loads12/24VDC equations drawing between 1 and 6 amps per hour.

Especially: want to understand cable or system loss calculations

Cheers
Brendan
brendan@technogreenie.com

2. ### mik3 Senior Member

Feb 4, 2008
4,846
70
Measure the resistance of the wire with a multimeter if it can measure small resistances accurate. Otherwise find the resistance of the wire per meter from the internet and multiply it by the length of your wire to get its total resistance.
When you find the resistance of the wire multiply it by the square of the current flowing through it to find the power losses in watts.

Another thing you can do is to measure the voltage drop across the wire with a high resistance multimeter (this is important as not to affect the voltage across the wire because it is very small) and the current through the wire. Then multiply the voltage with the current to find the power losses in watts.

3. ### thingmaker3 Retired Moderator

May 16, 2005
5,073
8

For calculating line losses, we begin by looking up the resistance per standard length of a conductor of given size. We then multiply by the length actually used. (Remember to count length as there and back again!) This tells us the resistance of the wire.

By multiplying the resistance of the wire by the amount of current flowing through it, we get the voltage drop across it. Applied voltage minus line loss equals voltage at the load.

I would give an example, but all of my wire charts are in ASE instead of metric. 3mm is roughly AWG#8, is it not?

4. ### brendan Thread Starter New Member

May 6, 2008
2
0
Thanks for the help, I think i get what you mean. i will give things a go.

Regards

Brendan