[POLL] Would you prefer a bigger battery or less SuperCharger tapering?

widodh · Sep 23, 2014

This weekend I went to München (Munich, DE) a roadtrip of 2.000km in total.

As much as I love the SuperCharger installations, I always get a bit disappointed by the tapering that occurs at the SuperChargers. ~100kW of power really adds range very quickly, but as soon as you go over >50% SoC the tapering becomes really annoying.

The 85kWh battery is big enough for me, but the tapering really slows you down.

While I know that a 110kWh battery would taper at a slower rate, what would you prefer? A bigger battery or a slower tapering rate?

So I voted for less tapering. I know, this requires chemistry changes for this to be achieved.

Yggdrasill · Sep 23, 2014

That is a tough one. I think I'd prefer less tapering, but as you say, a bigger battery is one way to achieve that.

tom66 · Sep 23, 2014

As I live in the UK, less tapering for me too. A bigger battery would rarely be used.

widodh · Sep 23, 2014

Yggdrasill said:
That is a tough one. I think I'd prefer less tapering, but as you say, a bigger battery is one way to achieve that.

Indeed, a bigger battery achieves that, but keep in mind it would be more expensive as well.

If for example my 85kWh could be charged with a average of 1C I would be very happy.

Yggdrasill · Sep 23, 2014

widodh said:
Indeed, a bigger battery achieves that, but keep in mind it would be more expensive as well.

If for example my 85kWh could be charged with a average of 1C I would be very happy.

Changing the chemistry can be just as expensive. Often higher power density means less energy density, so you might basically be choosing between 100 kWh battery pack and half as much tapering at equal cost. But the 100 kWh pack using similar cells as the 85 kWh pack would only decrease tapering by about 15%, so you might still be better off with the high power cells.

Other benefits of the bigger pack would be longer range and longer battery life. So that would also play a role.

spaceballs · Sep 23, 2014

I say add to poll
"Stronger AC system to cool Pack during SC for minimal tapering."
"New pack to accept external pre-chilled coolant from SC for minimal tapering."

widodh · Sep 23, 2014

spaceballs said:
I say add to poll
"Stronger AC system to cool Pack during SC for minimal tapering."
"New pack to accept external pre-chilled coolant from SC for minimal tapering."

Are you sure it is temperature related and not the cells themselves?

Yggdrasill said:
Changing the chemistry can be just as expensive. Often higher power density means less energy density, so you might basically be choosing between 100 kWh battery pack and half as much tapering at equal cost. But the 100 kWh pack using similar cells as the 85 kWh pack would only decrease tapering by about 15%, so you might still be better off with the high power cells.

Other benefits of the bigger pack would be longer range and longer battery life. So that would also play a role.

Ok, I agree. But thinking about Model III with a ~50kWh pack. Those users also want SuperCharging and a 50kWh would taper even faster/earlier. So a chemistry change would be very welcome to allow higher C rates for them as well.

ItsNotAboutTheMoney · Sep 23, 2014

Less tapering: thinking long term, for the sake of contention, you want people to be able to charge as fast as possible. Model 3 will sell a lot of cars with the smaller batteries instead of 85kWh+. You'll need to get them going.

martinve · Sep 23, 2014

I voted for bigger battery.
For these reasons :
- Price would be higher, but keep in mind that by the time they have a higher energy density, the price would be cheaper also.
- With a bigger battery, I shouldn't need to recharge that often, avoiding a supercharger. I don't mind charging at a lower speed when i'm at my destination. What I do mind is waiting to charge at a supercharger, even if it goes fast.
- Bigger battery gives me more flexibility to make changes on my travel plan, changes that were not planned. (example : woops, dad got a car problem, i need to pick him up...100km drive and I already drove 150km)
- 50% of a bigger battery (which should charge fast) should be more then enough range to reach my destination. Tapering would be less also since I'm not charging to max.
- With a bigger battery I'm not talking about a 100Kwh battery, but more like a 120Kwh or 150Kwh battery.

Highkick · Sep 23, 2014

I voted for less tapering.
For every day commute, the 85kWh battery is fine for me, i.e. I only charge at home. I use SCs only during holidays, so less tapering would mean less time at the SCs which would mean more people can SC. And I'm a bit anxious when all owners drive from Netherlands, Germany, Belgium to Sankt Anton for there skiing trip on the same day....

mknox · Sep 23, 2014

I live in the least prioritized Supercharger zone in the world where Tesla sells cars (Canada) so opt for the bigger battery.

widodh · Sep 23, 2014

ItsNotAboutTheMoney said:
Less tapering: thinking long term, for the sake of contention, you want people to be able to charge as fast as possible. Model 3 will sell a lot of cars with the smaller batteries instead of 85kWh+. You'll need to get them going.

That's what got me thinking as well. Model III will have a smaller battery (presumably), so you want them to charge fast.

Less queuing at the SuperChargers and shorter travel times.

I think it's a smart move of Tesla to have a 120/135kW SuperCharger already out there. A current Model S can't fully use it though, but future batteries probably will.

brianman · Sep 23, 2014

widodh said:
That's what got me thinking as well. Model III will have a smaller battery (presumably), so you want them to charge fast.

Less queuing at the SuperChargers and shorter travel times.

Which might mean Model3 drivers will begin to hate "Model S with A battery" cars for "taking too long" to charge.

Cottonwood · Sep 23, 2014

Less tapering and more Superchargers!

If a Tesla could accept 1.21 gW, then it would only take 0.25 seconds to charge 85kWh!

1.21 GigaWatts - How Many Teslas?

mknox · Sep 23, 2014

Cottonwood said:
...more Superchargers!

...in Canada !

Cottonwood · Sep 23, 2014

Cottonwood said:
...more Superchargers!

mknox said:
...in Canada !

...and everywhere. If there are more Superchargers around, then you have less need to charge into the taper.

Getting that last 20-25% of charge takes more time than the Tesla graph; it seems to take forever!!!

To your point of Canada, 5 or 6 more Superchargers could provide great, well-spaced Supercharger connections from Detroit through Toronto and Montreal to Boston that would not require charging deep into the taper!

widodh · Sep 23, 2014

brianman said:
Which might mean Model3 drivers will begin to hate "Model S with A battery" cars for "taking too long" to charge.

Even ones with B, C or D batteries. A full charge still takes 1.5 hours at a SuperCharger, so that averages about 50kW for 75kWh.

Cottonwood said:
...and everywhere. If there are more Superchargers around, then you have less need to charge into the taper.

Getting that last 20-25% of charge takes more time than the Tesla graph; it seems to take forever!!!

To your point of Canada, 5 or 6 more Superchargers could provide great, well-spaced Supercharger connections from Detroit through Toronto and Montreal to Boston that would not require charging deep into the taper!

True, true. But you can reduce travel times and SC occupation by charging quicker. The SC is capable of doing that, but the battery currently isn't.

LMB · Sep 23, 2014

(LMB spouse)

Tighter Supercharger spacing equals less time charging (to a point). There's a stretch of Superchargers in the Carolinas that are only about 120 miles apart. We try to arrive with around 20 miles left, so the charging stop is only about half an hour, even driving 80. The only time we've Supercharged to above 85% is trying to make Newark DE to Glen Allen VA or vice versa before the Woodbridge SC was live.

(Edit: I lied. I forgot that we charged to 95% at Santee South Carolina so we could spend a few days visiting Charleston without destination charging.)

(Edit 2: And LMB has an S85. I'd probably vote for less taper if it was an S60. Sorry about that, S60 owners.)

apacheguy · Sep 23, 2014

Voted for less tapering. Here in CA there is an abundance of SpC (and yes I want to see them continue to expand) and I have almost never felt inconvenienced by only having 85 kWh. What if Tesla could update the algorithm to hold 90 kW until 50%-55%? I think that would be amazing.

Cottonwood · Sep 23, 2014

widodh said:
Even ones with B, C or D batteries. A full charge still takes 1.5 hours at a SuperCharger, so that averages about 50kW for 75kWh.

But 80% only takes about 40 minutes. 75kWh * 80% / 40 min = 90 kW average charge rate ... Just don't charge that last 20% at Superchargers unless you really need it.

Most new Supercharger spacings seem to be at most 133 miles (214 km) apart. With that spacing, you can charge to 200 rated miles (322 rated km), a little less than 80% of an 85, and still drive quickly and/or deal with bad weather, consume 1.5x rated Wh's, and get to the next Supercharger.

widodh said:
True, true. But you can reduce travel times and SC occupation by charging quicker. The SC is capable of doing that, but the battery currently isn't.

The newest Superchargers are rated up to 135 kW out, but I believe that wiring from the Supercharger Cabinet to the Pedestal and within the car limits the current to about 333 Amps. During the initial phases of the charge in an 85, the Voltage is about 360 Volts, and 360 Volts * 333 Amps is 120 kW. 120 kW for an 85 and 105 kW for a 60 may well be the design limits of the wiring and connectors.

A 90 kW average for the first 80% is not bad, especially if the peak is limited to 120 kW by components other than the battery.

[POLL] Would you prefer a bigger battery or less SuperCharger tapering?

Bigger battery of less tapering?

Bigger battery

Less tapering at the SuperCharger

Fine with me as it is right now

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