If electricity were truly cost-free then it would certainly matter less to me. But for most of us we do pay for our electricity. Even if my solar array were far larger and supplied all our needs all year round, a far off dream, excess usage in the cars would mean less to export and be paid for. Not disagreeing with your premise but I don't think it is realistic.
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So… Highland is out…
- Thread starter boombap
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Interestingly at the moment the electricity for my wife's Model 3 Performance is free as Octopus is giving us 2 hour windows of free electricity a couple of times a week. This is excess renewables, normally around 2pm where it'll just go to waste so it's being given away for free. With her normal pottering around a 2 hour juice up even once a week is probably enough to keep it topped up, it's working at the moment.
Generally though you are right, there's a cost somewhere like not exporting as much electricity which you are paid for. But we aren't talking big numbers here, some rough calculations:
Range of car: 250 miles
kWh added: 75kWh
Efficiency: ~3.3 Miles per kWh
Cost per kWh: 7.5p (Intelligent Octopus)
Charge cost: £5.63
Cost per mile: 2.3p
Now let's say we have a more inefficient car. I'll keep the battery the same but the range drops. Normally now this would need to be a car with a larger battery.
Range of car: 150 miles
kWh added: 75kWh
Efficiency: 2 Miles per kWh
Cost per kWh: 7.5p (Intelligent Octopus)
Charge cost: £5.63
Cost per mile: 3.8p
Additional cost to run the second car over the first:
1 mile: 1.5p
100 miles: £1.50
1,000 miles: £15
10,000 miles: £150
This can seem a lot but now lets consider say my Diesel Land Rover:
Range of car: 650 miles
Tank size: 89 litres
Gallons: ~19.5
MPG: ~33.2
Cost per litre (Current UK average): 152p
Cost to fill: £135.28
Cost per mile: 21p
Additional cost compared to the second EV:
1 mile: 17.2p
100 miles: £17.20
1000 miles: £172
10,000 miles: £1,720
Someone moving from an ICE to an EV is going to be quite a bit better off with either of those EV's. Frankly though on my roughly 10,000 miles a year, I don't care if the EV costs me £150 more a year to put electricity in. It's pretty small in the scheme of things when I'm actually paying £1,720 more just to run my Disco compared to that inefficent EV. I would care though that the range of my second hypothetical EV is really short. This is why I care about efficiency for the moment but my ultimate interest is for them to get to a real world 400 - 500 mile range. And that's without having to go 55 miles an hour on motorways, a perfect 20C day with the AC off.
I think for the people that can afford EV's on this forum, £150 extra in your pocket each year isn't going to change your world.
There is of course the other green argument and more efficient is always important but will I think become less so once we get to a 100% renewable or nuclear powered grid.
WannabeOwner
Well-Known Member
Point of Order Sir!
Not usually. Rule of thumb would be 6% extra on the building cost. If you go down the route of no boiler (and no UFH / rads etc.) then you also have the benefit of no maintenance and no replacement of that item, and the reduction in capital cost too, so would probably get "a payback".
Retro-fit an existing house to Passive house (or EnerPHit) standard ... yeah, that is usually "unaffordable"
You'd be a lot more comfortable in the non-American-muscle house
Have you tried it in an EV (i.e. a 12 hour journey and having to stop for 20 minutes every couple of hours or so?
The reason I ask is that we used to drive to Alps skiing, usually twice a season, non-stop. 2 or 3 minutes to swap drivers in an Aire every 3 hours, one stop for fuel - probably combined with lunch, which we would either find a nice restaurant off the motorway, or motorway services and not dawdle. (Yeah, now we are more restricted for lunch because it has to also provide a 10-100% charge in the hour.
We were (way, way) younger then, and always arrived knackered.
Now, into retirement age, we do the same journey in EV and arrive in really good shape. The only difference is the the extra 20 minute stops. You know, just like the government adverts suggest that we should do
6% is a good amount when talking about a house though. How much more solar and batteries to go with it could you get with that?Point of Order Sir!
Not usually. Rule of thumb would be 6% extra on the building cost. If you go down the route of no boiler (and no UFH / rads etc.) then you also have the benefit of no maintenance and no replacement of that item, and the reduction in capital cost too, so would probably get "a payback".
Retro-fit an existing house to Passive house (or EnerPHit) standard ... yeah, that is usually "unaffordable"
You'd be a lot more comfortable in the non-American-muscle house
Have you tried it in an EV (i.e. a 12 hour journey and having to stop for 20 minutes every couple of hours or so?
The reason I ask is that we used to drive to Alps skiing, usually twice a season, non-stop. 2 or 3 minutes to swap drivers in an Aire every 3 hours, one stop for fuel - probably combined with lunch, which we would either find a nice restaurant off the motorway, or motorway services and not dawdle. (Yeah, now we are more restricted for lunch because it has to also provide a 10-100% charge in the hour.
We were (way, way) younger then, and always arrived knackered.
Now, into retirement age, we do the same journey in EV and arrive in really good shape. The only difference is the the extra 20 minute stops. You know, just like the government adverts suggest that we should do
As for comfort and I know this is abnormal for the UK but my current house is air-conditioned in all the rooms (Other than toilets / showers). The American way I guess but they can heat and cool any room to the level set. We tend to focus on heating in this country but it's getting hotter, cooling is also important I think at least for me.
Yeah I'm not saying I can drive 600 miles in a go. However that range gives me options, I can still stop where I want but doesn't need to have charging. I can go a good distance still when it's really cold. I can tow something for a fair distance, I can put a roof box on and not lose a ton of noticeable range. A 300 mile WLTP EV is more like a 250 mile range in real world when it's about 20C and 200 odd in the winter. Towing maybe 100 - 120 odd at a guess if it's a reasonable size / weight.
bkp_duke
Well-Known Member
WannabeOwner
Well-Known Member
Off topic here, but say £500K (i.e. exc. land) for the build, 6% is £30K, not hard to save £3K a year on heating/cooling and maintenance, with some allowance for the comfort and health benefits. Its a bit like EV vs ICE. EV is £10K more to buy, but there are long term savings, and other benefits. Nicer to drive (IMO !) and a portion of that £10K is available on resell - more so for the house I reckon
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Maybe I’m unusual, I’m kind of doubtful though, but on efficiency my thoughts are fairly simple
Stupidly high and I’m not interested, there’s no real excuse to be approaching 400wh/m
Stupidly low, if at the expense of sound insulation, slow performance and super skinny efficient tyres with compromised grip, etc then not interested.
In the 240-320wh/m range I’m more interested in range which is as much a function of battery, and performance. I could buy a RWD Tesla which is more efficient than the LR I own.
So, yes, efficiency matters at the extremes but not in the middle 75% range.
It’s the same as when I bought ICE, I never chose 50mpg over 40mpg cars, quite the opposite, I typically went for 6 cylinder engines. The super eco cars had no appeal, nor really did the v8 20mpg cars (although I owned one for 4 years)
Stupidly high and I’m not interested, there’s no real excuse to be approaching 400wh/m
Stupidly low, if at the expense of sound insulation, slow performance and super skinny efficient tyres with compromised grip, etc then not interested.
In the 240-320wh/m range I’m more interested in range which is as much a function of battery, and performance. I could buy a RWD Tesla which is more efficient than the LR I own.
So, yes, efficiency matters at the extremes but not in the middle 75% range.
It’s the same as when I bought ICE, I never chose 50mpg over 40mpg cars, quite the opposite, I typically went for 6 cylinder engines. The super eco cars had no appeal, nor really did the v8 20mpg cars (although I owned one for 4 years)
Yes I guess the brute force way won't help the EPC rating. That's a big heating / cooling saving for sure as well. Seems like it could be the way to go then.Off topic here, but say £500K (i.e. esc. land) for the build, 6% is £30K, not hard to save £3K a year on heating/cooling and maintenance, with some allowance for the comfort and health benefits. Its a bit like EV vs ICE. EV is £10K more to buy, but there are long term savings, and other benefits. Nicer to drive (IMO !) and a portion of that £10K is available on resell - more so for the house I reckon
Exactly this. In the past you'd not pick a BMW over a Mercedes or Audi because it say did a few more mpg, you wouldn't care. We are only more hung up on efficiency on an EV because the real world range isn't comparable to an ICE so it matters more. This won't last, probably will become a mute point towards 2030 - 2035 in my opinion but we aren't there yet.
I'm very much in this camp - as long as the efficiency is at least OK, my massive priority is usable range. It's not about being able to do 600 miles without stopping, it's the flexibility to go wherever you need whever you need and not need to be obsessed and spend hoursd beforehand and be forced to be regimented about exactly where to stop and for how long.
We recently travelled to Fort William for the Mountain Bike World Champs, and we had to pre-plan all of our exact stopping points and charge levels to ensure we could make it to the next place (there is a Tesla Supercharger in FW which is fantastic, but it's the only one for a wide area!), and whilst it all worked out perfectly as planned, it's still an added and permanent background stress that just doesn't exist with ICE. I'd never want to go back to ICE, but a decent amount of additional range would make the whole experience much more pleasurable, and I'd pay a relatively hefty amount extra for that.
Charging speed is also affected by the size of the pack. Make the pack lower capacity and it’ll also charge slower. This is why a Model S on a 100kWh can charge as quick as the Model 3 / Y’s on roughly 20kWh less. If you convert it to miles charged per hour the Model S is quicker.
This all assumes the car and not the charger is the limiting factor.
Oh yes, all about spreading the heat across a larger amount of cells.
800V helps with that so should make the smaller pack cars charge faster.
I do wonder if the smaller Tesla will ever arrive, presumably that would have a smaller pack size offering, presumably something like 50kWh useable and the current RWD pack.
I understood that 800v cars are slower to charge on anything other than an 800v charger ... which are presently relatively few in number... so maybe a strategy for the future. (They're limited by their DC/DC converter performance.) Bear in mind that smaller capacity batteries (all other things being equal) charge at a slower rate than higher capacity batteries.
They are, but it should be the future as it lowers temperature in the pack while charging, so it offsets the requirements for larger packs.
So instead of a big pack to allow for quick charging you can do for a slightly smaller pack with higher voltage.
bay74
Member
Can you find a source for that claim? Because at the end of the day each cell is still ~3.7V and requires a certain current to charge it. How the pack is arranged is irrelevant to an individual cell, and pack heat generation, except in the possible reduced wiring which connects all the cells. No?
800v architecture means half the current in all the auxilliary components associated with charging that handle the power, like the cables, the charge unit itself etc, I'd have thought that all plays a fairly significant role in keeping the temperatures down as current essentially = heat even if the voltage ultimately presented to the battery is the same.
I think the only reason why 800v architecture cars are slower on 400v is because they're designed for lower peak current. It's the opposite side of the same coin, if you ignore the battery cells for a moment, delivering 120kw at 400v requires the same 300a current as delivering 240kw at 800v. 800v charges seem to go to 350kw or arounf 440 amps, Tesla at 250kw on 400v goes to 625 amps. So put a 800v car with a 440 amp limit on a 400v charger and you'll only get 175kw hence its slower. If an 800v car could support 625amps, then it could theoretically peak charge at 500kw.
When it comes to the battery cells themselves, I'm not sure how much is in series of parallel but the current through say 100 cells in series x 3.7v might be 1a at 370v across the lot, but then you have a second bank of 100 x 3.7v to give 2a at 370v to charge 200 cells, whereas the higher voltage ,may allow both those banks to be switched onto series to give 1 block of 200 cells at 1a and 740v - I'm guessing, but you can see there are options in the way stuff is configuired.
I think the only reason why 800v architecture cars are slower on 400v is because they're designed for lower peak current. It's the opposite side of the same coin, if you ignore the battery cells for a moment, delivering 120kw at 400v requires the same 300a current as delivering 240kw at 800v. 800v charges seem to go to 350kw or arounf 440 amps, Tesla at 250kw on 400v goes to 625 amps. So put a 800v car with a 440 amp limit on a 400v charger and you'll only get 175kw hence its slower. If an 800v car could support 625amps, then it could theoretically peak charge at 500kw.
When it comes to the battery cells themselves, I'm not sure how much is in series of parallel but the current through say 100 cells in series x 3.7v might be 1a at 370v across the lot, but then you have a second bank of 100 x 3.7v to give 2a at 370v to charge 200 cells, whereas the higher voltage ,may allow both those banks to be switched onto series to give 1 block of 200 cells at 1a and 740v - I'm guessing, but you can see there are options in the way stuff is configuired.
This was my understanding. Of course I do expect Tesla to move to 800V at some point as can be some cost advantages and if the rest of the market is going that way they'll likely need to align eventually.
Smaller cells are probably only going to charge quicker if new chemistry also comes around. Maybe by that point even if they do charge slower than a larger pack, it'll still be quick enough that most won't care.
When I'm asking for more capacity, this doesn't mean I want it by just increasing current battery sizes with the same chemistry. I'd like to see that increased capacity come about more from improvements in chemistry. Nio can do a 150kWh pack that's only 20kg heavier than their 100kWh pack. Yes it is vastly more expensive now but it'll come down over time once production scales. 20kg is nothing really so it shouldn't really impact the efficency of the vehicle, it should I suspect charge faster than the 100kWh when you look at miles per minute added to the pack. Other than cost, there's no real negatives to this.
Now factor in say 2/3 of the country could charge their cars at home. They also can go further without charging so possible a trip someone plans that would have needed them to use public charging, now no longer does. This frees up public charging infrastructure and we don't quite need as much. I think less charging locations but all rapid chargers would be much better than the current plan of slapping slow or middling speed chargers all over the place. Be easier for maintenance to keep them all working as well.
We will of course have to litter the country with chargers before the batteries arrive at sensible pricing that could have avoided that though sadly.
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