EV database - how do they work out charging speed
Discussion
A 7 kW domestic charger it will, by definition, put in 7 kWh of charge over the course of an hour. If one KWh gets the car 3 miles then that 7 kWh gets 21 miles so the charging speed in terms of range is 21 mph (miles of range added per hour). On a rapid charger the car is able to take 46kW so each hour that is 46 kWh so 140 miles per hour range. Incidentally 3 miles per kWh is pretty poor 4 or 5 would be better and 45 kW charging rate is poor for a rapid charge by modern standards, 350 kW is a good speed now.
I always got a totally childish buzz when the Tesla displayed 350mph across the dash when is started charging..
I always got a totally childish buzz when the Tesla displayed 350mph across the dash when is started charging..
Cars have limits on charge rate in kwh, on AC thats usually 7kw single phase, 11kw 3 phase, might be 22kw on 3 phase and if you're Tesla it might be 17 kw.
Then DC charging also has a limit, sometimes 50kw, sometimes 100kw, sometimes more, as high as 250kw I've seen, but the chargers seem to go up to 350kw
So they take the max charge rate, then take the range and divide by the battery capacity to gice the speed - 300 mile range, 100kwh battery - 3 miles per kwh - if you can charge at 7kw then 7x3 is 21 miles per hour.
But the metric is massively flawed for DC charging as its the area under the curve not the peak rate that matters as for some EVs the peak rate which is quoted can be high, but the profile drops off quickly.
EV database is riddled with other mistakes too, they fail to recognise different batteries in different countries etc. as well as some of these fundementals.
Then DC charging also has a limit, sometimes 50kw, sometimes 100kw, sometimes more, as high as 250kw I've seen, but the chargers seem to go up to 350kw
So they take the max charge rate, then take the range and divide by the battery capacity to gice the speed - 300 mile range, 100kwh battery - 3 miles per kwh - if you can charge at 7kw then 7x3 is 21 miles per hour.
But the metric is massively flawed for DC charging as its the area under the curve not the peak rate that matters as for some EVs the peak rate which is quoted can be high, but the profile drops off quickly.
EV database is riddled with other mistakes too, they fail to recognise different batteries in different countries etc. as well as some of these fundementals.
saaby93 said:
350kW 
What sort of volts and current is that?
What's the cable like?
and how does that compare with the power requirements of a small town?
800v so lower current than the 250kw 400v chargers. The cables are water cooled. What sort of volts and current is that?
What's the cable like?
and how does that compare with the power requirements of a small town?
As for comparisons to small towns, thats one of the issues Tesla face. They have a number of locations where they require 1MW or more supplies due to the number of chargers. The average house has a max rating of about 23kw, often lower, but the energy companies assume nobody is peaking at the same time so apply diversity calculations. Assuming they're working on about 5kw for each house concurrently (at 15p a kwh that would be an annual electric bill of over £6k although they have to cater for peaks so not unreasonable), thats 200 houses
Heres Johnny said:
saaby93 said:
350kW
What sort of volts and current is that?
What's the cable like?
and how does that compare with the power requirements of a small town?
800v so lower current than the 250kw 400v chargers. The cables are water cooled. What sort of volts and current is that?
What's the cable like?
and how does that compare with the power requirements of a small town?
As for comparisons to small towns, thats one of the issues Tesla face. They have a number of locations where they require 1MW or more supplies due to the number of chargers. The average house has a max rating of about 23kw, often lower, but the energy companies assume nobody is peaking at the same time so apply diversity calculations. Assuming they're working on about 5kw for each house concurrently (at 15p a kwh that would be an annual electric bill of over £6k although they have to cater for peaks so not unreasonable), thats 200 houses
Does the water cooling continue into the car?
saaby93 said:
800V = Thats 450A - starter motor cable is only 100A.......
Does the water cooling continue into the car?
I meant liquid cooled, not sure water is the best for what they want and Tesla for instance just quote "liquid cooling".Does the water cooling continue into the car?
As the other Jonny says the fluid doesn't go into the car, however the cars themselves are also liquid cooled, more so than some people realise, and when supercharging at full chat the cars can get quite noisy when all the fans kick in to cool the fluids which are colling the batteries etc, Many a new owner asks the question whether their car is ok when it happens
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