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this what i need fred?
Polo + Micra
nah posted it for a laugh:S
I'm guessing you are trying to be smart there? Or actually stating you posted it for a laugh?
Polo + Micra
smart arse mode tbh
i know fred is good with cars but that's electricity so i'm guessing you'd be better off asking someone who knows about electricity (current carrying capacity of cables etc.)
Polo + Micra
well it's more about the volt drop you get on smaller cables and being as it only runs at 12-14v any volt drop is noticed
so starting it going to pull best part of 200A if not more which is over the current rating of 25mm² but it's only a short period so shouldn't do too much damage
but i'd say you could see easy 50A of demand from the whole car so you start noticing things like the lights being dim fan being slow etc
one other thing people need to remember is that fuses are there to protect cables and nothing else
so starting it going to pull best part of 200A if not more which is over the current rating of 25mm² but it's only a short period so shouldn't do too much damage
but i'd say you could see easy 50A of demand from the whole car so you start noticing things like the lights being dim fan being slow etc
one other thing people need to remember is that fuses are there to protect cables and nothing else
You can calculate the volt drop easily for a given cable with ohms law. But basically the smaller the CSA cable the higher the resitance will be and the greater the volt drop will be.
ie.
V = I*R
A quick google says
50mm2 is approx 0.3Ω per 1km, so 5m = 0.0015Ω
20mm2 is approx 0.8Ω per 1km, so 5m = 0.004Ω
So for 100A flowing for a nice round number.
100A*0.0015Ω = 0.15v Drop between the start and end of the cable for 50mm2
100A*0.004 = 0.4v Drop between the start and end of the cable for 25mm2
Then this continues for the rest of the electrical system, but all this has been calculated and factored in when renault designed the looms to place it at and acceptable level for the component it is supplying.
Sometimes they get it wrong/make it cheaper and problems arise, old headlight looms come to mind (especially jap stuff).
ie.
V = I*R
A quick google says
50mm2 is approx 0.3Ω per 1km, so 5m = 0.0015Ω
20mm2 is approx 0.8Ω per 1km, so 5m = 0.004Ω
So for 100A flowing for a nice round number.
100A*0.0015Ω = 0.15v Drop between the start and end of the cable for 50mm2
100A*0.004 = 0.4v Drop between the start and end of the cable for 25mm2
Then this continues for the rest of the electrical system, but all this has been calculated and factored in when renault designed the looms to place it at and acceptable level for the component it is supplying.
Sometimes they get it wrong/make it cheaper and problems arise, old headlight looms come to mind (especially jap stuff).
I've done mine with 4AWG - which is about 22mm squared
This is what the auto-electricians recommended for a 172 alternator
Runs fine - starts easy, charges fine. Put a fuse either end of the cable - cost me about £50 for the cable, connectors properly done (not home-crimp s**t), heatwrap, grommet through firewall and fuse boxes and fuses.
I can post pics if you want as the car's stripped out - or check my progress blog
This is what the auto-electricians recommended for a 172 alternator
Runs fine - starts easy, charges fine. Put a fuse either end of the cable - cost me about £50 for the cable, connectors properly done (not home-crimp s**t), heatwrap, grommet through firewall and fuse boxes and fuses.
I can post pics if you want as the car's stripped out - or check my progress blog
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