Alternator Wiring

[swifty]

I am goining to renew the charging cable from the alternator. The alternator is 12V/60Amp. I have some 10mm2 cable. Will this be suitable.

 

[lenseman]

Need to know a bit more about your 10mm cable?

Is it 10mm as in 'Flat Twin and Earth' household mains wiring or 10mm being the diameter of the actual conductor?

Secondly, how many strands of wire goes to make up this 10mm conductor?

Thirdly, what is the type of insulator and what colour is the insulator and is it a new length or wire or have you pressed it into service from another area or use.

Car alternator outputs usually use 98/010 guage wiring and the insulator is brown in colour. It has to be multi-strand to allow for engine movement and vibration.

 

[Alex_Blackwood]

You need a minimum of 25 mm square, multistrand cable. If your cable run is much more than 2-2.5 mtrs. I would use 30mm. to allow for volt drop.

 

[lenseman]

Errrrrrm?? /forums/images/graemlins/confused.gif

Isn't 25mm square about 1" by 1" ????

This is large enough to allow the supply of electricity for a large town and would be a bit overkill.

 

[TiggerToo]

err no... it is more like 5mmx 5mm

 

[lenseman]

even that will quite happily handle about 150 Amps?

Need to know what cable the OP has to hand and is hoping to use? /forums/images/graemlins/wink.gif

 

[swifty]

The cable is battery cable 10mm2 supplied by Barden

 

[Anthony]

An important question: what is the length of the cable run (and whats it connecting to)?

Ants

 

[RAI]

For 60A, Sterling Products recommends 25 mm2 up to 1.5 m long and 30 mm2 for up to 4 m long. Try to get "silvered" copper flex for maritime applications. You could treble up your 10 mm2, but it would not look so good.

 

[pvb]

Gosh, you've had some odd replies! Your 10mm2 cable is certainly too small. Alternator cable needs to be somewhat over-specified, to minimise voltage drop and ensure maximum charging efficiency. You should be using at least 25mm2 for a cable run of up to a couple of metres, and heavier still for a longer run.

Alternator cable also needs to be very flexible, because it's subject to a fair bit of vibration. Flexible cable is also much easier to install. You should look for "flexible starter cable" with around 200 strands. Cable is described by the number of strands and the diameter of the strand in mm. So, for example, cable described as 196/0.40 has 196 strands, each 0.4mm diameter, and has a cross-sectional area of about 25mm2. This sort of cable would be ideal for your need.

 

[tobble]

Hmm, bit of clarification required I think.

Firstly, like Lenseman says, you need to clarify what sort of cable you have. I'm guessing it's single core, andusually when printed on the sheath, 10mm refers to 10mm^2 (mm square) cross section. by geometry you should be looking at a conductor about 2mm across. Also need to know how long it's going to be.

cable sizing depends on two factors;

1. can the cable handle the amps (i.e. not get hot under load)
2. Will the voltage drop be tollerable

for the former, this reptutable renewables installer reckons 8.37mm square cable will take 65 Amps, so if my assumption is right you're ok on that front.

the second is a bit more complicated to work out, but basically you want as little voltage drop as possible, and IMHO 10mm sq is nowhere near big enough, especially if the batt is more than say 1 m from the alternator.

 

[Dave_Rolfe]

If it's any help (after much advice from this forum)I have just replaced the cable to my 55A alternator with a length of 25 sqmm cable. Reasons were to carry full alt. output to Sterling Charger and to keep voltage reduction to a minimum.

Pleased to say after all the help I had it now all works.

Still don't quite understand how the original thin cable from the alternator output to the starter motor carried all those amps without burning out though.

 

[halcyon]

You can carry 75 amp on 10 mm cable, does depend a bit on type, but in this case tri-rated.

Why not just wire to the starter motor feed ? this will be rated to carry far more amperage than the alternator, and only needs a couple of foot of cable.


Brian.

 

[NormanS]

when I was at school, there was a huge difference between 25mm square, and 25 square mm. I suspect that there still is!

 

[pvb]

[ QUOTE ]
when I was at school, there was a huge difference between 25mm square, and 25 square mm. I suspect that there still is!

[/ QUOTE ]Indeed there is, but I'm surprised you didn't learn basic maths nomenclature.

 

[Alex_Blackwood]

I did say 25 mm square not 25 mm squared! That is across sectional area of 25 mm.
They really are a pedantic lot on this forum I would have thought that you would have made allowances for poor uneducated Haggis!

 

[CliveG]

I have just brought some 25mm2 cable for rewiring our battery set-up.

The best price I could find was from Vehicle Wiring Products

I know it is not tinned but we will be dipping the ends in a solder bath before installation.
The old un-tinned cabling had lasted for 20 years as far as I could tell and was o.k. until it was immersed in 5m of muddy salt water along with the rest of the boat.

No connection with the company, just hapy with the price and the very quick delivery (ordered Saturday p.m. delivered Tuesday)

 

[pvb]

[ QUOTE ]
The best price I could find was from Vehicle Wiring Products

[/ QUOTE ]Anyone contemplating buying cable should also look at Acorn Engineering, who are even cheaper.