Battery Electric Vehicle News / Enjoying the Transportation Revolution

2nd_time_buyer

thevilla said:

Lighter or fewer batteries = fewer lighter batteries required.  That's where optimisation of EVs will be achieved.

Yes, you are right to a degree. However, with a perfect regenerative braking system, then mass becomes irrelevant because the energy required to accelerate can be recouped. We are some way from perfect regenerative braking but nonetheless mass of EVs is far less important than for ICE vehicles. Remember as well that mass is only relevent when accelerating  - the vast majority of energy is expended at constant(ish) speed overcoming aerodynamics.

Solarchaser

Grumpy_chap said:

Surely, the ideal approach is not to achieve longer range through simply having bigger batteries, but to achieve longer range through having more efficient cars (reducing losses between plug to road).

The largest batteries currently are around 100 kWh / 400 mile range.  A UK domestic single-phase installation can only charge at slightly more than 7kW, so an empty-to-full charge is 14 hours which leaves 10 hours in the day to cover leaving for work right back to home to the family.  A larger battery that takes any longer to achieve an overnight charge seems of limited benefit in the majority of cases.

However, a car that can cover 800 miles on that same 100 kWh battery - then we'd be talking

Plug to battery seems to be around 90-95% efficient in my testing of the Tesla, and If you can find a way to convert electricity from one voltage to another, or from ac-dc without creating heat, then you will become a very wealthy person as many many people have been trying to achieve that for many many years.

Motors are almost 100% efficient, again with the heat problem, though much much less than ice engines obviously. 

I've seen quite a few articles stating that from battery to road is about 80% and so with theoretical perfect regeneration you would have 60% regen.
The losses are gonna be hard to remove, because its mostly inertia, rotating mass and tyres that causes the problem there.
Now yeah you could get rid of some of that by mounting motors on the hubs, but then you have a shed load of unsprung weight, and thats not good, nevermind what the knocks and bumps would do to an electric motor.

So in short, I dont think there is really too much more can be done with socket to road efficiency,  certainly nothing earth shattering.
I think 8 miles from one kwh is next to impossible,  a little more than a 100w bulb pushing 2 tonnes for a mile...

Moving to your other point,  you still seem to struggle with the notion of
A. Work Place charging, where 3 phase would be expected and so 11kw charging would have you sorted empty to full in 10 hours.
And 
B. Pretty much no-one does 400 miles a day, and then 400 miles the next day and so on and so on, so the times you would be running empty to full would be the absolute exception, for the vast vast majority of users, topping up 2-4 hours at 7kw would be more than enough.

You seem to be stuck on filling up the battery from empty every day, but you don't fill your current car from empty every 2 days just now (assuming you have a vehicle which does 800 miles empty to full and you run it to empty every single time).

I've now done just a smidge under 10,000 miles in 5 months of having the Tesla and I can count on one hand the amount of times I e charged it from empty to full.
It's at 60 odds just now, and the place I'm going tomorrow has 11kw chargers, so I'll plug in there and top up for a couple of hours, as that's what you do with electric cars, top up when available, not run to empty.
I think this is just a mindset you will get into if/when you get an EV.
You have to remember also, you are simply parking in your driveway as normal (assuming you have one) and plugging in, no diversions to petrol stations, no waiting in line to pay etc, it really is much simpler

Verdigris

And "filling up" for free, in summer, if you have solar panels.

Or you can have an ICE car and pay £1.40+ per litre.

orrery

Verdigris said:

And "filling up" for free, in summer, if you have solar panels.

Largely mythology, in my experience. I've been trying since 2014, pre Zappi, splashing out on 6 amp granny cables to maximise my solar input and then realising that I'll never recover my money.

I've long since concluded, bearing in mind that most people need to use their cars during the day when the sun is shining, that charging is best left to cheap rate overnight and solar is best used to offset the higher daytime tariffs.

orrery

2nd_time_buyer said:

There is very little scope to increase efficiency for EVs

That said, there seem to be significant differences between the efficiencies delivered by different manufacturers.

With a Leaf you tend to average around 4M/kWh, in a Kia Ioniq maybe nearer 5.5. I'm reporting figures from someone who has owned a large number of EVs and is making a 1:1 comparison.

orrery

2nd_time_buyer said:

Yes, you are right to a degree. However, with a perfect regenerative braking system, then mass becomes irrelevant because the energy required to accelerate can be recouped.

I agree, but that will depend on the driver.

The situation is similar to me driving in the Peak district, which I do frequently. Dragging up steep hills and then regenerating down the other side.

I see no discernable difference in M/kWh between driving in the Peaks and round home on Bedfordshire roads where you are hard pushed to find any hills at all.

Martyn1981

Verdigris said:

And "filling up" for free, in summer, if you have solar panels.

Or you can have an ICE car and pay £1.40+ per litre.

Yep, been fun charging mostly from PV, but it does mean plugging in much more often ..... first world problems!

Switched back to 7kW E7 charging early in Oct, as the PV doesn't generate enough now, especially being E/W, and we want to use that excess to run the A/C unit, so that we don't need the GCH (very close to switching it on now though). At a rough guess I'd say the Apr to Sept BEV charging has been 50% full PV, and 50% part PV, where gen excess was more than 1kW so worth charging.

Fantastic combination for those able to benefit from both PV and a BEV. And looking at the bigger picture, daytime charging of BEV's, be they at home, or at work, is a great way to absorb daytime PV excess on the grid.

EVandPV

Admittedly I've been working from home this year but the vast majority of my charging from mid March to September has been from PV, mostly trickle charging at 1.4kw.

Verdigris

Martyn1981 said:

Fantastic combination for those able to benefit from both PV and a BEV. And looking at the bigger picture, daytime charging of BEV's, be they at home, or at work, is a great way to absorb daytime PV excess on the grid.

I'm intending to install around 10kWp of PV. The plan is to have virtually free motoring in the summer, when I'll want to be out and about exploring my new home area, and getting a reasonable contribution to running the ASHP in winter, when I'll be at home more of the time.

Grumpy_chap

Solarchaser said:

Moving to your other point,  you still seem to struggle with the notion of
A. Work Place charging, where 3 phase would be expected and so 11kw charging would have you sorted empty to full in 10 hours.
And 
B. Pretty much no-one does 400 miles a day, and then 400 miles the next day and so on and so on, so the times you would be running empty to full would be the absolute exception, for the vast vast majority of users, topping up 2-4 hours at 7kw would be more than enough.

You seem to be stuck on filling up the battery from empty every day, but you don't fill your current car from empty every 2 days just now (assuming you have a vehicle which does 800 miles empty to full and you run it to empty every single time).

I think my comments have been poorly expressed.  It was in response to the article suggesting batteries having "five times the capacity" of standard ones:

EVandPV said:

PANASONIC’S NEW TESLA BATTERY LASTS FIVE TIMES LONGER AND COSTS HALF AS MUCH

https://www.independent.co.uk/life-style/gadgets-and-tech/panasonic-tesla-battery-electric-car-b1946866.html

For most people most of the time, charging is at home from single phase power supply and I think it reasonable that the desire would be to achieve a full charge overnight.  

That then imposes a practical limit on battery capacity at around 100 kWh.

Comments from EV owners in this thread seem to suggest that around 4 m/kWh is a realistic "ball-park" figure for efficiency.

So that gives a range of around 400 miles, which is sufficient for most cases.

So, Panasonic making a battery that is "five times the capacity" is of limited real-world advantage for most people in most cases.  The 500 kWh battery would provide 2k mile range, but that is of limited practical benefit for car EVs. 

The benefit for car EVs is in cheaper, smaller (dimensionally), lighter batteries that can still reliably store 100 kWh capacity and avoid challenges associated with heat through being denser.

Then, with that 100 kWh battery constraint, the benefit is in achieving longer range from that battery through greater plug-road efficiency.  If we are currently at around 4 miles / kWh, comments just made in this thread indicate towards around 5 miles / kWh as a practical limit.  That means an increase of 25% in range but also a decrease of 25% in operating cost and CO2 burden which is certainly not to be sniffed at.

Obviously everything above relates to EVs in the context of cars / light vans and the limit value of a battery having 500 kWh capacity.  The benefit may be far greater if the definition of EV is expanded to include goods vehicles, construction plant, which imposes more complex demands.

As an aside, to allow for a comparison of an ICE to EV in consistent units, the following web page tells us that 1 litre of diesel is around 11 kWh energy:
https://www.withouthotair.com/c3/page_31.shtml#:~:text=calorific values: diesel: 10.7 kWh,petrol: 9.7 kWh/l.
So, around 50 kWh per gallon
At 60 mpg, that is around 1.2 miles per kWh so the EV 4 m/kWh is fantastic.
Did I get that maths correct?  60 mpg divided by 50 kWh/gallon.