[Paul]

It dawned on me that while we all go around discussing the pros and cons of who is and isn't benefitting from the rapid charging networks and how charging could or should be distributed, for the most part we seem to be missing a trick.

I know others have said so, but for a truly "all electric" future, we're surely going to have to do better than we have now (or at least, drop a lot of what we have)?

As range increases, as does battery capacity, as does the energy required to "refuel". Topping up, full charge, it doesn't matter. In percentage terms you need more energy to fill a bigger battery. (My physics teacher would be SO proud I took that much in)...

Anyway, for what most people "rapid" we're in the 40-60 kW range at present, which surely just wont be good enough as battery levels increase.

Tesla Superchargers deliver what, 120-135 kW and therefore, with the increased battery capacity, a comparible charge/dwell time for those of us in our LEAFs.

But is that enough? I know things will creep, not leap, it's how the industry works, but surely the infrastructure should be way AHEAD of what we need, not just enough?

Perhaps 22 kW should be seen as the "normal" charge rate and 120 kW the "fast", then we can watch as battery capacity creeps up?

I don't know, I don't have a big battery, but surely just about every charger below a certain threshold (so all the 3/6 kW chargers in Milton Keynes and car parks around the world) are really too slow, even for a decent dwell time or overnight stop?

I don't know, but it seems we need a real upshift in charging technology before we see any leaps in battery tech.

This isn't a "Tesla has it right, everyone else has it wrong" discussion, it just seems that we all want more pure battery range, but is the charging network ready for that? I don't think it is.

 

[Paul_Moxhay]

I totally agree Paul. The "rapid" charge of today will surely be seen as the "fast" charge of tomorrow as capacity and so charge rates increase.

I am eexpecting new tech that hasn't yet hit the market to help with this. Totally different battery chemistry is already in late research/early production staus that will potentially revolutionise EVs in the years to come. Ones that charge at many times that of today and have significantly higher energy density. We will need much fast chargers than even the tesla Superchargers I expect.

That is why I am so disappointed to see so much money being put into today's charging tech. It could all be obsolete in a few years.

 

[flipper]

My understanding of the Tesla Superchargers (and all the technology around it) is that they are designed to be able to deliver a lot more than they currently do - in other words, to keep up with demand.

But are the current Rapids actually that bad? If you consider that, when charging a Leaf, the charge rate drops off above 50% and then drops off considerably above 80%. If you had a bigger battery, presumably the charge rate would do the same, but 50% of a 40kWh battery is (obviously!) considerably more than 50% of a 24kWh battery and so you'd get more range for the same charge time. (Or have I missed something?)

 

[andrew*debbie]

What about the thousands of 3.6kW chargers being installed at homes? That is fine for charging a 24kWh pack, but may not be enough when EVs ship with 40kWh or larger packs.

 

[jontracey]

Two things to consider, for tesla to be able to charge at 120-135kw they need to actively manage the battery, heat or cool it before applying large quantities of power, this obviously adds cost to the vehicle.

1. Delivering more power probably means more cooling to preserve the life of the battery aka extra cost.

2. Also you have to consider how this huge amount of power is being provisioned, I understand from the rapid charge network guys that a lot of sites they survey cannot cope with 50kw Chademo so it will be a small number of sites that can cope with multiple 150+kw chargers on the go at one time.

The reality is once you have range the requirement (at least in a country as small as the UK) to rapid charge goes down so do you really need 500miles of charge in 30 mins, its nice yes but need, I am not sure.

 

[Paul]

The reality is once you have range the requirement (at least in a country as small as the UK) to rapid charge goes down so do you really need 500miles of charge in 30 mins, its nice yes but need, I am not sure.

You say that (and I take your point) but if I'm not rapid charging then my "slow" charging still has to be fast enough to top me up properly either while at work or asleep (say 8 hours) and give a decent boost in far less time, if I'm not relying on "rapids"?

 

[Alexander Sims]

I totally agree with you Paul.
I'm really not on here to boast about anything but with my Roadster (53kWh pack) if I get back late, I just about get a full charge overnight on a 7.4kW charge. It takes around 8 hours once you have factored in loses for cooling the battery.

I would guess that in 5 years time people expect EVs to have close to 200 mile range which will bring the battery sizes to similar to the Roadster...

50kW CHAdeMO/CCS/Type 2 is simply not Rapid anymore, due to the drop off at the top half or so of the battery, a fullish 'rapid charge' is going to take an hour or more... It is crazy how far ahead Tesla are of all other charging networks still and even their current speeds are surely not going to be the best we can expect in 10years time.

I'm not sure what the answer is but at 22kW the model S charges in around 4 hours and that's almost as long as an i3 on 7kW. With bigger batteries comes the need for much faster charging and I simply don't see any point in these 3/3.6kW charging posts paid for by the taxpayer. To me, if the government spend our money then they really should make it future proof to an extent. Why oh why don't they only give 7kW stations for free because that way it can still be used in 15 years time when the house has been sold and the new owner buys a current EV.

 

[Alexander Sims]

Two things to consider, for tesla to be able to charge at 120-135kw they need to actively manage the battery, heat or cool it before applying large quantities of power, this obviously adds cost to the vehicle.

1. Delivering more power probably means more cooling to preserve the life of the battery aka extra cost.

2. Also you have to consider how this huge amount of power is being provisioned, I understand from the rapid charge network guys that a lot of sites they survey cannot cope with 50kw Chademo so it will be a small number of sites that can cope with multiple 150+kw chargers on the go at one time.

The reality is once you have range the requirement (at least in a country as small as the UK) to rapid charge goes down so do you really need 500miles of charge in 30 mins, its nice yes but need, I am not sure.

Regarding the issue of sites not having the capacity, I am no engineer but can't a sizeable battery help buffer that problem? A 'trickle charge' of 30kW (or whatever the site can manage) into a 2mWh battery or more could then supply peak charges of 130kW quite easily. I know it is all down to cost as well but it will be interesting to see what the Tesla battery factories impact is in the energy storage market.

 

[jontracey]

Regarding the issue of sites not having the capacity, I am no engineer but can't a sizeable battery help buffer that problem? A 'trickle charge' of 30kW (or whatever the site can manage) into a 2mWh battery or more could then supply peak charges of 130kW quite easily. I know it is all down to cost as well but it will be interesting to see what the Tesla battery factories impact is in the energy storage market.

Yes but at what cost, I am pretty sure 2mWh batteries are expensive, if not I want one for home

 

[andrew*debbie]

Minor niggle. A 2mWh battery is very small since lower case m is milli. 2MWh. SOrry I'm an engineer.

 

[smartie]

There is always new technology "just around the corner" - however, no-one would be driving EVs today if everyone waits until the perfect infrastructure is in place for 200+ miles range EVs costing £15k.

I do agree however that government funding should have focussed on rapid charging infrastructure (as is the case with a number of other countries e.g Japan) and leave slower charging infrastructure to be met by private companies at competitive prices given that it is relatively low cost.

 

[Jimbo]

7kw is giving me round 20miles of charge per hour, so a 10hr overnight charge would be enough for a full charge (so far haven't gone below 50 miles remaining). This is with a P85. If the battery was even bigger, then 7kw wouldn't be enough.

But a bigger battery is only needed if the public infrastructure isn't there.

With the supercharger, you don't need to wait for a full charge. A SC gives meaningful range to a flat battery in around 20 minutes.

In theory, ABB or another charger manufacturer could now make a Type 2 charger that goes all the way from 3kw to 135kw SC. Put some of those in every petrol station and suddenly it is a non-issue.

For example, BP and ARCO have installed rapid chargers in Paris. Need to see more of this.

 

[Talon]

I guess it depends on how far you need to go.

 

[Edd Beesley]

Let's make some assumptions. I drive a car that consumes 333wh/mile, or 3 miles per kwh. When I stop to rapid charge I don't want to wait longer than 30 minutes. In those 30 minutes I want to pick up 200 miles of range (66.6kwh). I'm then going to drive for three hours and have to stop again, (I drive at an average of 66.6mph between stops). That means my car needs about 300 miles of range, so that it isn't empty when I stop and I don't neccesarily need to make a detour to find a rapid charger, and also so that when the charger has added 200 miles I am not yet near the very high SOC value, so charge rate hasn't dropped too much. So in 30 minutes, I want 66.6kwh, I need an average charge rate of 133kw, a peak rate of probably 200kw. In terms of my battery, I need 100kwh usable. If that 100kwh is the 90% usable window of a battery I need a 111kwh battery.

I think this is a good balance between cost and capability in the medium term.

 

[Matt Beard]

We are close to the point with Supercharging that even most "corner cases" are satisfied.

Overnight charging at home or a hotel is slow, and borderline acceptable at 7kW for corner cases. 100-150kW is just about enough for all expected car uses as long as you don't "drive until you drop" and if the chargers are located in convenient places.

Overnight charging only becomes an issue if you arrive at your home/hotel late after a very long trip (so with an almost flat battery) - then eight hours sleep plus a couple of hours for breakfast and a little pottering will give you 70kWh or so of charge which should easily manage the first part of the next day's trip.

That first leg would have the overnight 70kWh available to use at (from above) 333Wh/mile, giving about 210 miles. At the maximum speed limit of 70mph that would be three hours. Any slower and it will take longer before you need to stop - however you really shouldn't drive for much more than three hours without at least a short break. It you wanted to "splash and dash" at your first break you should be able get about 30kWh back in 15 minutes on a current Supercharger - which would do you nearly another hour and a half. By then you would have travelled about 300 miles, and will be due a meal break. Give that half an hour and you will be close to where you started at the beginning of the journey so will be able to do another 200 miles or so before another break. Unless you are doing Lands End to John O'Groats you are probably at your destination by now, or will be with no more than a short top-up.

However, if you have a bigger battery pack, and don't start by trying to overnight-charge a totally flat pack, there will be plenty of margin in the battery for longer stints or a bit of lead-footed driving!

 

[leave]

Regarding the issue of sites not having the capacity, I am no engineer but can't a sizeable battery help buffer that problem? A 'trickle charge' of 30kW (or whatever the site can manage) into a 2mWh battery or more could then supply peak charges of 130kW quite easily. I know it is all down to cost as well but it will be interesting to see what the Tesla battery factories impact is in the energy storage market.

Hmmm, given that we've just established a Nissan 24kWh battery pack cost £4,500 (ignoring the trade in value), a 2MWh battery pack will cost in the region of £375,000. Plus a building to put it in. Plus the charging system. Plus the charging to the cars. Probably plus some active heating/cool of the super battery.
There are also the "round trip" losses to take into account, some of that 30kW 'trickle' will heat the battery and won't make it into the cars. There is also the wear and tear on the super battery - it'll need to be replaced at some point.
It's an interesting idea, but I think economics will get in the way... sadly...

 

[andrew*debbie]

Yes but at what cost, I am pretty sure 2mWh batteries are expensive, if not I want one for home

Do you have room for 2MWh of battery? The 500kWh Li-Ion battery at Orkney Storage park takes up 2 sea containers.

That battery can deliver 2MW of peak power, something a home system doesn't need to do.

 

[andrew*debbie]

.
It's an interesting idea, but I think economics will get in the way... sadly...

They will if you build it out of brand new Leaf batteries. Tesla plan to use their packs which are less expensive per kWh.

(ignoring the trade in value)

The used packs have 75% of the initial capacity at 1/5 of the price. Maybe 75% isn't enough for a car, but it is fine for stationary storage.

 

[Matt Beard]

Hmmm, given that we've just established a Nissan 24kWh battery pack cost £4,500 (ignoring the trade in value), a 2MWh battery pack will cost in the region of £375,000. Plus a building to put it in. Plus the charging system. Plus the charging to the cars. Probably plus some active heating/cool of the super battery.
There are also the "round trip" losses to take into account, some of that 30kW 'trickle' will heat the battery and won't make it into the cars. There is also the wear and tear on the super battery - it'll need to be replaced at some point.
It's an interesting idea, but I think economics will get in the way... sadly...

Still pocket-change compared to building and running a hydrogen refuelling station!

 

[jontracey]

Do you have room for 2MWh of battery? The 500kWh Li-Ion battery at Orkney Storage park takes up 2 sea containers.

That battery can deliver 2MW of peak power, something a home system doesn't need to do.

Ok maybe that a little excessive but a nice battery storage unit that I can charge up of solar and cheaprate power and use during the day would be very nice

I could put a sea container at the bottom of the garden, hide it in a bush wife would never know