This doesn’t seem to apply to 110v what what I’ve been able to tell, unless they are adding an extension cord.
But level 2 or DC chargers appear to have a requirement of about 3-6 feet. Why is this?
What is the importance of the length of cable?
In: Technology
tl;dr you need big cables to use big charging amps, and big cables weight a lot. you have a maximum length because you have a maximum weight you can support with a cheap plastic clip.
the resistance of a wire is more or less constant, for a given length/cross section.
if you double the cross section of the wire, you halve the resistance (more or less).
if you double the length of it, you also double the resistance.
if you want to send 110v, 8 amps 15 meters, 2mm twin and earth is a perfectly acceptable size of wire to use (that’s standard 14 gauge household wire, for people that use freedom units).
if you want to send 220v, 20 amps 15 meters, you can still use that same 2mm cable.. but by the other end of the cable, you’ll probably only have 212volts.. and slightly warm cable. as a minimum you’ll want to use 2.5mm (14 gauge), or even 4 or 6mm (that’s 12 or 10 gauge). .
more cross section = less resistance to current.
when you’re talking about level 2 vehicle chargers, you’re talking about 240 volts, and **40** amps of current… which means that in order to still have 240 volts at the other end, you need to use 10 or 12mm cross section cable (8 or 9 guage)..
the problem with 12mm cross section wire (and bear in mind that that’s the measure of just the conductor, not including insulation, then a ground layer, then an outer layer of insulation).. is that it weighs quite a lot.
a meter of 12mm level 2 charging cable weighs in at roughly 2lbs (slightly less than a kilo).. so 2 meters of it (about your limit of 6 feet) weights roughly 4 lb .. and you have to support that weight with the clip on the end of the charging socket.. usually at some extension, because the cable is attached to the car at one end, and the charging station at the other, and usually not supported at any point over it’s entire span. … and that puts a lot of strain on what is basically just a plastic plug and a plastic retaining clip. you could make the retaining clips stronger, but they have to be weak enough to break off if your car is hit whilst it’s charging, or if you try to drive off without unplugging it.
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