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Discussion Starter #1 (Edited)
Edinburgh council has recently produced a report stating that they will need to install a total of 69 chargepoints to support electric vehicle use in Edinburgh by 2020. This includes 9 rapid chargers, 35 fast chargers and 25 slow chargers. By 2023, 211 chargepoints are forecasted to be required. This includes 23 rapid chargers, 111 fast chargers and 77 slow chargers.

Most interestingly is their plan for the type of chargers. The slow 7kW AC is fairly normal as is Rapid 50kW DC. However they plan on installing the highest number of Fast chargers and are planning on them being 22kW DC. Reading the report I had assumed that they were just getting muddled up between AC and DC and really meant a 22kW AC Fast Charger that is common throughout the UK. However in the breakdown in costs they restate the fact that these are 22kW DC chargers and show the expected costs for them which are only marginally cheaper than 50kW Rapids.

This seems like a really odd plan. I believe there are currently only two 22kW Rapids in the UK. One in the far North of Scotland and and one at Dundee University where the available power is limited.

I was always under the impression that the reason 22kW AC posts exist is because where the power is 3 phase they are hardly any more expensive to buy and install. Obviously a reasonably big issue with them is that most EV's can't actually charge at 22kW AC which is presumably why Edinburgh plan on making them DC despite the massive extra cost involved and the fact that they can only charge one vehicle unlike a regular 22kW post which can charge two EV's simultaneously.

As someone who wants to switch to an electric car but doesn't have off-street parking, I applaud Edinburgh for at least having a plan for off-street residents to charge but this plan seems seriously flawed. The charge time of 22kW DC is a bit of an odd one really at two or three hours. Fast enough that you need to move your car when done but not fast enough to actually want to stay to near your car. Pretty good speed for a shopping centre/cinema but a PITA if you get home at 9pm as you'd then have to go back out a midnight to move your car, only for nobody else to probably want to use the post. Surely more useful to install 5x the number of double headed 22 or 7kW AC chargers and be able to charge 10 cars between 9pm and 9am instead of just one and still save money?

Link to the report here: http://www.edinburgh.gov.uk/download/meetings/id/58745/item_71_-_electric_vehicle_infrastructure_business_case

Edinburgh Chargers Cost.png
 

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There are quite a few 22kW rapids on the chargepoint scotland network IIRC - all, I suspect, 50kW-capable units hampered by the extreme cost of enlarging the power supply at a remote point.

This plan seems bizarre. It would be interesting to see how much usage urban 22kW rapids got; I fear prolonged overstaying would be rampant given the 3+ hours this will take to charge "modern" large battery EVs.
 

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There are far more cars can use 22kW DC than would be able to get 22kW out of an AC post, so if all they have available is three-phase 32amp it may make perfect sense to install reduced power DC chargers. That £5k installation cost could go up by a lot if they also have to upgrade the power supply to the site.

Two to three hours for a full charge is only going to apply to cars needing between 44kWh and 66kWh. Those will be people who've done at least 130 miles since their last charge but didn't pass a 50kW charger. So stick these in in places where most journeys are short and people will be getting a top-up without having drained the battery, or have short range EVs where 22kW is a full charge.
 

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There are far more cars can use 22kW DC than would be able to get 22kW out of an AC post, so if all they have available is three-phase 32amp it may make perfect sense to install reduced power DC chargers. That £5k installation cost could go up by a lot if they also have to upgrade the power supply to the site.

Two to three hours for a full charge is only going to apply to cars needing between 44kWh and 66kWh. Those will be people who've done at least 130 miles since their last charge but didn't pass a 50kW charger. So stick these in in places where most journeys are short and people will be getting a top-up without having drained the battery, or have short range EVs where 22kW is a full charge.
You could install precisely ten 7 kW chargers for the price of one 22 kW DC charger.

I know what I’d rather see.
 

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Tbh it would be a better use of the money to ditch the 22kw units and stick 5extra 50kw units in and a load more 7kw posts in charging bays.
 

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Discussion Starter #6
Presumably they are worried about not being able to have a supply that copes with more than 22kW at the locations they want to install them. I still think they would be able to charge more cars, more conveniently and for a much lower capital cost with two double headed 7kw posts which would have the added benefit of redundancy incase one post fails.
 

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Actually, plenty of reports showing that charging times for Zoe at least, 43kW versus 22kW are not significantly different. Yes of course that is AC.

Maybe, they do have a point that city based charging should be just for "city cars". If that is the case, then they will need strict time limits of say 1/2 hour max per each session (card, account or car ID lockouts ) to ensure high availability,
 

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What is installed today will represent the infrastructure that supports the EV transition that will take place over the next 10-20 even 30 years. As such it seems crazy to size / specify this infrastructure arround the spec of current short range EVs that are already outdated and were designed many years ago.

As such it would only seem sensible to specify at least 22kW AC and 150kW DC chargers so as to future proof this investment. Both are backwards compatible for existing cars and both can be reasonably easily linked to demand management and battery backup systems.
 

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It’s not the size of your battery that counts, but the range of your daily commute.
That works for a home charger but not a public charger. They need to provide several days or even a week's worth of daily range.
 

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Well, the Worcestershire Polar rapids were mostly 22kW DC until I stirred some fuss and they were set back to the intended 40kW (50kW ... pha!! No chance .. 104A DBTs)...
 

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That works for a home charger but not a public charger. They need to provide several days or even a week's worth of daily range.
I guess it depends.

If the car is going to be left there for most of the day or overnight, then even 11 kW is too much.

If they need a rapid charger, then this clearly needs to be as fast as possible, so 50 kW or above.

I’ve not found even 11 kW chargers that useful. They’re too slow to replace rapid chargers and too fast for destination charging.
 

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I guess it depends where they are located and how the typical dwell time fits with the chargers proposed.

While i have a car that cant rapid charge, i also think that rapid charging is kinda a bit crap. Its a necessary evil for long journeys, but for regular charging i really dont want to sit there watching the battery fill up for half an hour every few days...

I want to charge the car while i'm doing something else.

A slow 3/7kw post works fine if i'm charging somewhere i'm likely to be "all day" or "most of the day". A normal rapid might work if theres something i can do for "half an hour". 22kw slots fairly nicely in between for dwell times of "an hour or two".

Having options is always useful, and it makes sense that we'll start to see more options pop up. A 22kw DC unit can serve two purposes... It can be used where you want a rapid but there isnt capacity for a 50kw unit. But it can also be used in place of a more traditional 22kw AC unit, and (assuming its triple head) can then provide that 22kw to almost every EV around, rather than just a small subset. If they continue to require simultaneous AC and DC like they do with the rapids then even better!
 
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