Tesla - And whats it really like owning an EV?

Tesla - And whats it really like owning an EV?

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TooMany2cvs

29,008 posts

125 months

Tuesday 17th February 2015
quotequote all
Working out theoretical maximum charge rate is straightforward.

A Tesla has an 85kwh battery. That will take one hour to fill at 85kw, or 85 hours at 1kw. Multiply hours by kw (power) to get kwh (capacity), or divide 85kwh by kw to get hours.

You are getting your home electricity at 230v (single phase) or 415v (three phase). Multiply the voltage by the amps (current) to get kw.
So...
13A 230v = 3kw = 28hrs
32A 230v = 7kw = 12hrs
32A 415v = 13kw = 6.5hrs

These are, of course, all theoretical rule-of-thumb absolute maximum rounded-off figures ignoring inefficiencies and the fact that the charger won't pull absolute maximum current.

Before you even contemplate the three phase option, have a chat with your electricity supplier. The cost will be _horrendous_, not least because you will need some of your front garden dug up to lay the extra cabling to the house. And that's always assuming there's three phase available without changing transformers etc (in an urban area - there probably will be, but in a rural area, you may not be so lucky).

Scuffers

20,887 posts

273 months

Tuesday 17th February 2015
quotequote all
Lot of assumptions there, 3phase 32a is not 13kw.

Also, the charger and battery are nothing like 100% efficient, be lucky to achive ~80% (are there any real figures for this?)

Also, lot of houses have 3 phase, was common to support night storage heaters etc, (we have 100a 3phase at home)

TooMany2cvs

29,008 posts

125 months

Tuesday 17th February 2015
quotequote all
Scuffers said:
Lot of assumptions there
Yes, I know there are. That's why I caveated it with the line about it being an absolute theoretical maximum, assumptions-a-go-go, reality intrudes, etc etc.

Scuffers said:
3phase 32a is not 13kw.
415 x 32 = 13,280 - unless I'm missing something?

Scuffers said:
Also, lot of houses have 3 phase, was common to support night storage heaters etc, (we have 100a 3phase at home)
Really? Wow. Urban streets certainly tend to have all three going down, with one phase split off per property - but I didn't think it common to actually have all three supplied to residential properties. As I said, life's very different out here in the boonies - our little enclave of eight houses and one working farm is supplied from a single-phase transformer, which is fused to 200A between the lot of us. I don't even want to know how much they'd charge to change that... (especially since they only changed it last January... and didn't put a 3-p one in then, even though there are all three coming in on the HV lines, one of which is just ignored!)

bp1000

Original Poster:

873 posts

178 months

Tuesday 17th February 2015
quotequote all
Maff said:
Yes, charging can be a bit hard to understand at first. In tesla terms the car comes as standard with one onboard AC charger. This will mean:

That's it really for charging. Any other type or speed is irrelevant, just the above. However the 3.6kw is very slow to charge due to size of battery.

This winter longest run I did on one charge has been 220 miles. I could have probably gone 235 if I really pushed it to zero! And that's sitting at 70 or so on the motorway.
In the summer I could get 250 driving the same style, maybe a fraction more if I slowed to 60mph!

Hope this all helps! :-)
Yes thank you! I'm glad it is capable of decent range. I would be happy with 200-250.

If i buy i just need to get the Nissan adapter thing then. I suppose a capable for charging from a normal plug for example when i'm at a holiday rental is not advised as things might get a bit hot and it seems you don't get a normal plug lead anyway.

Scuffers

20,887 posts

273 months

Tuesday 17th February 2015
quotequote all
TooMany2cvs said:
Scuffers said:
3phase 32a is not 13kw.
415 x 32 = 13,280 - unless I'm missing something?
you're missing something! - the fact it's 3 phase!

AC three phase amps to kilowatts calculation formula:

The real power P in kilowatts is equal to square root of 3 times the power factor PF times the phase current I in amps, times the line to line RMS voltage VL-L in volts divided by 1000:

P(kW) = √3 × PF × I(A) × VL-L(V) / 1000

So kilowatts are equal to square root of 3 times power factor PF times amps times volts divided by 1000:

kilowatt = √3 × PF × amp × volt / 1000

or

kW = √3 × PF × A × V / 1000

so, assuming a PF (Power Factor) of 1 (it's a charger so should be 1 or close to):

Kw = 1.732 x 1 x 32 x 415 /1000

= 23Kw

or if you do it the other way of counting the 3 phases as 3x240V singles:

Kw = 1 x 32 x 240 /1000

= 7.68Kw

x3 (3 phases) = 23Kw.

TooMany2cvs

29,008 posts

125 months

Tuesday 17th February 2015
quotequote all
Scuffers said:
you're missing something! - the fact it's 3 phase!
<grin> I sit corrected...

Scuffers said:
AC three phase amps to kilowatts calculation formula:

The real power P in kilowatts is equal to square root of 3 times the power factor PF times the phase current I in amps, times the line to line RMS voltage VL-L in volts divided by 1000:

P(kW) = v3 × PF × I(A) × VL-L(V) / 1000
...mildly baffled, but firmly corrected...

Scuffers

20,887 posts

273 months

Tuesday 17th February 2015
quotequote all
welcome to 3 phase electrics!

way to think of it is this:




between any phase and neutral is 240V
between any phase and another phase is 415 (not 240 X 2)

Each phase is a sine wave, the voltage quoted is the RMS (Root Mean Square) of said wave:



if you draw a line vertically on that plot, and measure between two waveforms, that's your 415V, you're never going to measure from one phase peak to another.

that make sense?


Maff

611 posts

266 months

Tuesday 17th February 2015
quotequote all
Scuffers said:
Ah, OK, thanks for that, makes more sense...

done a bit of digging, looks like it's actually only a 2 phase solution, ie, each onboard charger runs of (between phase) 415v (begs the question, can you have a 3rd charger onboard?)
Hmm, It does draw 32a from each phase on my supply. It maybe there is something splitting the three phase input to each charger though?

slippery

14,093 posts

238 months

Tuesday 17th February 2015
quotequote all
All I know, is if I put mine on charge overnight on a 32 amp Podpoint charger at home, it should be ready to go every morning.

Scuffers

20,887 posts

273 months

Tuesday 17th February 2015
quotequote all
Maff said:
Hmm, It does draw 32a from each phase on my supply. It maybe there is something splitting the three phase input to each charger though?
OK, how do you know that?

with 2 chargers connected delta (ie. across phases to get 415v) you will have all three phases connected, but you will have only 2 phases loaded (that's not to say no current is passing up all three legs, just that it will not be an equal load).



that shows 3 loads on 3 phases, if you remove one of the loads, that's what you have.

bp1000

Original Poster:

873 posts

178 months

Tuesday 17th February 2015
quotequote all
Anyone know what the Tesla high power charger is that says "coming mid 2015" - is it just a tesla branded home wall charger that does 30 / 32amp ?

I stopped by my local charge point today. Ecotricity, 1 side was DC i assume this was the 50kW point that i need the £350 adapter for. The other side was AC. I assume this is very slow to charge? Does the Tesla come with a cable to cover all options, e.g. supercharger, home box, and the AC side at ecotricity. I assume the 50kW just plugs into the adapter and then into the normal capable tesla supply.

ta


TooMany2cvs

29,008 posts

125 months

Tuesday 17th February 2015
quotequote all
Scuffers said:
welcome to 3 phase electrics!

way to think of it is this:


...
that make sense?
No, but since I'm not planning on going anywhere NEAR three phase with a screwdriver, that's absolutely fine...

Actually, that image does start to explain the star-delta stuff with three phase motors et al, which I've never understood, either.

pboyall

176 posts

120 months

Tuesday 17th February 2015
quotequote all
bp1000 said:
Anyone know what the Tesla high power charger is that says "coming mid 2015" - is it just a tesla branded home wall charger that does 30 / 32amp ?

I stopped by my local charge point today. Ecotricity, 1 side was DC i assume this was the 50kW point that i need the £350 adapter for. The other side was AC. I assume this is very slow to charge? Does the Tesla come with a cable to cover all options, e.g. supercharger, home box, and the AC side at ecotricity. I assume the 50kW just plugs into the adapter and then into the normal capable tesla supply.

ta
The £350 adapter will only actually give you 25kW on the Nissan branded units. Tesla has had to reduce the current draw as when Nissan built the units they intended them for little Leafs sipping electricity for 30 minutes, not Teslas guzzling for hours :-) Upgraded units are being rolled out which will give the full 50kW, but you will be better off finding a 120kW supercharger if you can, for obvious reasons!

The £350 adapter is what you plug the rapid charger into, then into the car. The same socket on the car takes Supercharger cables and "regular" Type-2 cables.

The AC side of a Nissan rapid is very very slow compared with a Supercharger, on a Tesla. If you have dual chargers you can get 22kW (it's three phase) but you will probably find you are only getting 11kW.

Tesla's home High Power Charger, if you are talking about the one I think you are, is an 80 Amp unit - specially fitted and requires new wiring. But does charge you up a lot faster than a 7kW 32 amp will.


bp1000

Original Poster:

873 posts

178 months

Wednesday 18th February 2015
quotequote all
pboyall said:
The £350 adapter will only actually give you 25kW on the Nissan branded units. Tesla has had to reduce the current draw as when Nissan built the units they intended them for little Leafs sipping electricity for 30 minutes, not Teslas guzzling for hours :-) Upgraded units are being rolled out which will give the full 50kW, but you will be better off finding a 120kW supercharger if you can, for obvious reasons!

The £350 adapter is what you plug the rapid charger into, then into the car. The same socket on the car takes Supercharger cables and "regular" Type-2 cables.

The AC side of a Nissan rapid is very very slow compared with a Supercharger, on a Tesla. If you have dual chargers you can get 22kW (it's three phase) but you will probably find you are only getting 11kW.

Tesla's home High Power Charger, if you are talking about the one I think you are, is an 80 Amp unit - specially fitted and requires new wiring. But does charge you up a lot faster than a 7kW 32 amp will.
Thanks! All this info has filled in a lot of gaps

I have been talking to the Mrs about it again tonight gauging her thoughts on the potential inconvenience of having an electric car. The possible scenarios that arose were

We take a trip down south once a year. Exactly 200 miles away with 2 superchargers on the way and 1 within 20 miles of where we stay. So no prob there and back. Perhaps slightly off route I guess. But we will need juice when we are there for 1-2 weeks and therefore will need to make use of primarily the Nissan chargers.

What's peoples experience of being limited to where you can park? Now I discovered that the Nissan chargers only do 25kW, is there etiquette on using the spaces? I mean if we park up and go off for a few hours is that a bad thing? On the flip side do you find you get somewhere needing to charge and the bays are full?

What do you do with the inconvenience of having to wait or being restricted on where you park or having to go out of your way to charge up? Does this bother anyone?

Admittedly this only happens when you are away from home and your home charger.

peterperkins

3,148 posts

241 months

Wednesday 18th February 2015
quotequote all
TooMany2cvs said:
Before you even contemplate the three phase option, have a chat with your electricity supplier. The cost will be _horrendous_, not least because you will need some of your front garden dug up to lay the extra cabling to the house. And that's always assuming there's three phase available without changing transformers etc (in an urban area - there probably will be, but in a rural area, you may not be so lucky).
Like anything the cost might be horrendous. But not always wink

We recently had 3 phase installed for a heat pump and electricity export capability..
Initially Northern Power Grid quoted £28k frown and wanted to put a new 100kva transformer on an adjacent overhead HV line then dig up the garden to run it 50M to the garage. (No thanks)

However it pays to do your research first on what infrastructure is already installed nearby.
Look at any low voltage overhead lines, talk to your neighbours about what they know of any cables etc.
Then use the dig safely scheme to get hard copy plans of the local underground cables.

Doing that I found there was a 70 Waveform 3 phase cable underground inside my property boundary and running underneath the garage less than 6M from where I needed it. It was in fact where our single phase supply was coming from.

We were the last house on the line up a small lane and it supplied us and the two other adjacent houses.

So I politely suggested to NPG that we connect to the existing cable. They dropped the quote to £6k but then still wanted to dig up 50 yards of my neighbours shared driveway and cause a right mess.
Eventually I convinced them to connect on my property to the existing cable and it all came in at about £1.6k which I consider to be a bargain.

They certainly didn't make much money, as a whole stream of people then came to sort it out over a couple of weeks.

1) Man to discuss connection and infrastructure reqd from customer . Visit 1 hr.
2) 2 x Men to dig hole and thread cable through customer installed ducting. 1hr
3) Jointer & mate to do connection to underground cable and install fuse point in garage. 3hrs
4) Man to disconnect old single phase and cut underground cable.
5) 2 x men to back fill hole in ground. 1hr
6) 2 x men to deliver extra gravel to repair drive. 0.5hr

Win some lose some I suppose wink

So with an 80A per phase 3 phase supply I could just about run the 50kw Tesla charger with a bit to spare for the house.
So assuming a few losses then the 85kwh Tesla Battery would charge from 0 to 100% in <2hrs.

Not sure the neighbours would like me pulling that much power for long as it would def dim the lights.

Edited by peterperkins on Wednesday 18th February 07:40

Rick101

6,959 posts

149 months

Wednesday 18th February 2015
quotequote all
How sexist! I demand at least 4 of them men are replaced by women immediately!

That's a big saving, bet you was chuffed with that. I'm pretty sure the 6k cost would have been about right.

Jon1967x

7,175 posts

123 months

Wednesday 18th February 2015
quotequote all
Scuffers said:
welcome to 3 phase electrics!

way to think of it is this:




between any phase and neutral is 240V
between any phase and another phase is 415 (not 240 X 2)

Each phase is a sine wave, the voltage quoted is the RMS (Root Mean Square) of said wave:



if you draw a line vertically on that plot, and measure between two waveforms, that's your 415V, you're never going to measure from one phase peak to another.

that make sense?
Aren't we 230v now? smile

This is bringing back far too many memories of my degree

TooMany2cvs

29,008 posts

125 months

Wednesday 18th February 2015
quotequote all
peterperkins said:
Like anything the cost might be horrendous. But not always wink

We recently had 3 phase installed for a heat pump and electricity export capability..

Doing that I found there was a 70 Waveform 3 phase cable underground inside my property boundary and running underneath the garage less than 6M from where I needed it.

...it all came in at about £1.6k which I consider to be a bargain.
A grand and a half for six metres of cabling... Bargain... <whimper>

Scuffers

20,887 posts

273 months

Wednesday 18th February 2015
quotequote all
Jon1967x said:
Aren't we 230v now? smile

This is bringing back far too many memories of my degree
well, yes and no.

since we harmonised with EU, it's been quoted as 230v +10% - 6% (216.2 - 253v)
in reality, it never changed from 240v

read this: http://www.twothirtyvolts.org.uk/pdfs/site-info/Ex...

all that said, with the proliferation of solar PV, the actual measured voltage can vary a lot, for example, at home, in a smallish village, the supply shows 251/241/243.




IN51GHT

8,777 posts

209 months

Wednesday 18th February 2015
quotequote all
Our Zoe is a 22kW battery, so at our standard 13.5p per unit it works out at £2.97 for 100-120miles of driving. That's still pretty cheap.

Add to that the ability to charge, for free, from a fast charger in under an hour, and the fact that more shopping centre & supermarkets are offering free charging the real cost per mile is likely to be under 2P per mile.