cable from solar controller to battery

[shortcircuit]

Scenario:

I have a 10A 12v load which requires a 4m long cable, 1.0mm² will suffice (fused 10A). To ensure minimal volt drop I choose, say, a 10mm² cable and because the cable ends will now not fit in the terminations I would fit bootlace ferrules or wire pin crimps. Now if not available, I could cut the end conductors down to say 4.0mm², this would still be 4 x larger than the original cable, and whilst the overall current carrying capacity of the cable is reduced it is still greater than the design current of the circuit.
So whilst it may not be the correct way to terminate the cable it can be done without reducing the current carrying capacity below the design current of the circuit.

Please do not confuse capacity with load. I made a simple statement that does not change, "Cutting cores reduces the current carrying capacity of the cable" I make this statement in order that it is understood that if you use a suitable length of cable to carry the load you require which may be near the cables maximum current carrying capacity you cannot cut cores off just to make it fit a terminal

 

[maingate]

I agree entirely with sparrks. There seems to be a hysteria about fitting heavy cables, for solar panels especially.

I have happily used 2.5 mm sq domestic 3 core cable for well over 2 years. When I changed to mostly 4 mm sq dedicated solar cable, there was no difference at all in input to my batteries. Some people are horrified that I did not use 6 mm sq and predict doom, gloom and flat batteries. :wacko:

There are websites which, if you feed in a few bits of information, will give you the percentage voltage drop over a given length, at a given voltage for a given cable diameter. The difference for 6 mm, 4 mm and 2.5 mm for most solar installations is insignificant. The cost between 6 mm, 4 mm and 2.5 mm cable prices however ARE significant. The newbie to solar asks on forums for info but usually gets the wrong info.

If they took the time to look at the wiring used by the likes of Fiat, Ford and motorhome converters, they would see just thin a cable needs to be to work OK.

 

[sparrks]

Volt drop, Ref method C 70°C thermoplastic 2 cables dc

csa mm² (mV/A/m)

1.0mm 44
1.5mm 29
2.5mm 18
4.0mm 11
6.0mm 7.3
10.0mm 4.4
16.0mm 2.8
25.0mm 1.75

Just a quick indication of the volt drop in various cable sizes in mV x A x m

 

[Byronic]

I've used 2.5mm sq. multifilament twin core rated @ 27 Amps for my 2X60W (c.8A max. output) panels, installed 16 years ago with no problems, nor should there be. Solid conductors, as has been mentioned should never be used in a vehicle...... vibration work hardens the copper and naturally it will eventually break.

 

[1978lovebus]

Domestic wiring is not flexible enough agreed. as to reducing the number of strands to fit the regulator nothing wrong with that as the length involved is too short to exhibit any heating losses. Over a long distance the greater the dia of the cable the better overkill does no harm whatsoever, generating leccy in the winter when there are only milli amps charging a battery losses need to be absolute minimal. There is more than one right in this world. I think an HNC in electrical and electronic engineering
is sufficient for me to give an informed opinion.

I agree, But dont forget to check to see if their are diodes fitted whether inline with the + of the cable from REG to Panel or on the control box of the panel, as this will result in reverse feed at night, also make sure the connections on the joints are good as you may result in some resistance (Ohms Law) which will result in loss.. My qualification in vehicle electrics and electronic principles BTEC 2 with distinction gives me sufficient room to add to the thread :lol-049:, there is some good advice on here that has been given.. I have myself fitted solars, regs, fuses, BIG batteries, Inverters, Wind turbine, consumer box, connecters that can handle the amperage and all the wiring to go, if you need help PM me....

I know you were asking about the REG to Batt and size of wire, select cables and connecters that will continously carry a minimum of your REGS output amps with a max lenght of 1.5mtr.. I used AWG12 30amp 79 strand wire at a couple of foot in length with an inline fuse to match output of the REG....

Dont forget the flux capacitor when it hits 88mph, how much current will be used when the solars are at that speed... lol