Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)

[jpet]

Howdy Jan, yes you are correct.

View attachment 111492

Thanks, KB!
We don't know if lolachampcar went "all-the-way" during this session.
It can take quite some time to reach the 0A end-point at times.

4.197V seems to be the highest value.

 

[pupik]

It looks like CELL or brick #54 is just under 2.9 at 0%--i wonder if that is the low voltage fault setting in the main BMS?

Cells during driving (by load) declined to 2.6V, when I stopped it started to going up again. #54 (2.888V) was the weakest I think, but it could go up after a while.
The snap (picture) is made right after the ride.
A rest of the energy can be nicely seen in energy meter behind a driving-wheel when it's less than 30kWh, the car turns off.

Didn't you drive further and use up the 4kW anti-bricking reserve--How did you override the anti-brick to allow further driving?

I was just still driving and driving when SOC already shown 0km (0%)
I think it's not Energy Buffer 4kWh yet.

And so your pack is fine after the torture test--and no cells hold at 4.2 for 100% soc?

I recharged to SOC 100% to line up cells. I normally charge only 80% max. 90%
Graph is made after disconnection from charger, voltage drops to < 4.2.V.
At the end of charging was 4.2V max.
I don't know why charging stopped on 98%. Maybe was met a condition, current < 50mA per cell. Maybe high charge 22kW.

 

[pupik]

my Tesla-scanner working in real time...
for example heater on/off is nice "Disco" :biggrin:
resolution for voltage is high 0.001
all cells is very balanced
sorry, video is bad

 

[jpet]

my Tesla-scanner working in real time...

I think you need to make the video public. We get a "This video is private" note.

 

[pupik]

I think you need to make the video public. We get a "This video is private" note.

sorry...
now?

 

[jpet]

sorry...
now?

Yes! The Tesla dance! Now we only need to add a beat. :tongue:

 

[Andyw2100]

sorry...
now?

I was able to view it, so I think you fixed the access issue.

 

[flathillll]

 

[JRP3]

Where did you find that, and why is the specific energy so poor?

 

[Fallenone]

On the official website for Powerwall, it is showin 6.4 kWh instead of 7 kWh now. I think this is the result of this thread.

 

[flathillll]

you think wrong. tesla has always stated 6.4 usable at 25C

stationary storage always states usable capacity going back to the days of lead and iron and sodium

 

[Fallenone]

But on their website just a few days ago it says 7 kWh. 7 kWh has always been the "face value" since last year too.

you think wrong. tesla has always stated 6.4 usable at 25C

stationary storage always states usable capacity going back to the days of lead and iron and sodium

 

[stopcrazypp]

But on their website just a few days ago it says 7 kWh. 7 kWh has always been the "face value" since last year too.

Right, that is correct. It seems they are counting the round-trip efficiency of 92% in at 6.4kWh. However, hard to tell if it has anything to do with this thread or if things changed as it reached production (first deliveries just recently happened in Australia). Like I speculated with the S pack design, the Powerwall pack design may not have been finalized until recently.

For example they are still surveying reservation owners about their setup (namely people with microinverter based systems). I don't think they have finalized what kind of equipment they are including yet with the Powerwall (they may end up also providing an AC based system instead of only the DC one originally assumed).
https://cleantechnica.com/2016/02/16/tesla-sends-surveys-powerwall-reservation-holders/

 

[flathillll]

But on their website just a few days ago it says 7 kWh. 7 kWh has always been the "face value" since last year too.

I see what you mean and I apologize for misunderstanding. Yes face value has recently been updated, not sure if it is because of us or because legally if you advertise 7 that means 6.5-7.0+

6.4 must be advertised as 6 or 6.4, but the data sheet has always stated 6.4 since launch

 

[stopcrazypp]

I see what you mean and I apologize for misunderstanding. Yes face value has recently been updated, not sure if it is because of us or because legally if you advertise 7 that means 6.5-7.0+

6.4 must be advertised as 6 or 6.4, but the data sheet has always stated 6.4 since launch

If you are talking about datasheet then you are correct after doing some digging. Datasheet always stated 6.4kWh at 25C. Website ads stated 7 kWh. I guess you are both correct.

 

[Fallenone]

No need to, just friendly discussion here:smile:

I see what you mean and I apologize for misunderstanding. Yes face value has recently been updated, not sure if it is because of us or because legally if you advertise 7 that means 6.5-7.0+

6.4 must be advertised as 6 or 6.4, but the data sheet has always stated 6.4 since launch

 

[scaesare]

View attachment 111545

Interestingly, a 20mmx70mm cell has ~33% more volume than a 18mmx65mm cell. Yet the rating on that cell would seem less than 33% more than the the 18650's that Panasonic currently sells.

 

[kennybobby]

Interestingly, a 20mmx70mm cell has ~33% more volume than a 18mmx65mm cell. Yet the rating on that cell would seem less than 33% more than the the 18650's that Panasonic currently sells.

It's not likely a strict function of volume, but the capacity limits may be thermally constrained by the surface area from which heat can radiate--the surface area increased about 20% and the capacity increased 21%.

 

[AWDtsla]

Interestingly, a 20mmx70mm cell has ~33% more volume than a 18mmx65mm cell. Yet the rating on that cell would seem less than 33% more than the the 18650's that Panasonic currently sells.

If more nominal current is expected for the cell the volume may be taken up by additional electrode.

 

[Johan]

Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usa...

It's not likely a strict function of volume, but the capacity limits may be thermally constrained by the surface area from which heat can radiate--the surface area increased about 20% and the capacity increased 21%.

That doesn't sound right. Sure a larger volume to surface area ratio would limit performance at high C rates, but likely not with regular and low loads? And as has been much discussed in this thread aren't we assuming that nameplate capacity is measured under favorable conditions i.e. no high temperatures and slow discharge?

Also having heard Elon and JB saying they're not married to 18x650 makes me think this isn't some particular sweet spot dimension.