How did they get to a 70kWh battery pack?

[glhs272]

Charged again today, this time from 2% (did not dare to run out) - 100% and got 59 kWh charged energy. Matches perfectly to 0-100% charge equals 60 kWh.

I would very much like to know how many kWh there is available below 0% on the 60 or 85? Any of you ever tried to run out of juice?

Speaking for my self, I always rated the battery based on how many kWh you can extract from it. I assume that the charging process adds inefficiencies, thus energy not going into the battery.

 

[Benjamin Brooks]

Exactly. If you input 59kWh then the amount that goes to the battery is probably ~90%. 90% would be ~53kWh useable energy into the battery.

Charged again today, this time from 2% (did not dare to run out) - 100% and got 59 kWh charged energy. Matches perfectly to 0-100% charge equals 60 kWh.

I would very much like to know how many kWh there is available below 0% on the 60 or 85? Any of you ever tried to run out of juice?

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[llavalle]

Exactly. If you input 59kWh then the amount that goes to the battery is probably ~90%. 90% would be ~53kWh useable energy into the battery.

90% efficiency is when using the onboard chargers. I've personally measured around 92% efficiency when charging @ 80Amps on my HPWC. And I calculated it that way : kWh measured using a power meter VS kWh counted by the car.

In that case (DC Charging) we have no clues what the car is reporting. Actual kWh back in the pack? Including losses to internal resistance or not (that's not 10%!) ?

In any cases : SQLCPH : just take your car (any time) and pop up the energy monitor screen. Multiply Wh/mi * estimated Miles. That will give you usable Wh in the pack left. Then do a simple cross-multiplication using the rated range to get the 100% usable Wh.

On my 85D, I get around 77-78 kWh.

 

[SQLCPH]

Exactly. If you input 59kWh then the amount that goes to the battery is probably ~90%. 90% would be ~53kWh useable energy into the battery.

I am not so sure.. When you charge DC from the super charger the kWh meter will show what you charge on your battery. I did the same charge recently on SuC and got 54 kWh on a 90% charge.

When you charge AC the car will obviously convert from AC to DC however the power measurement (probably a calculated power from voltage and current) are most likely done at the same point regardless what you charge your TMS with. Bottom line. The kWh meter you read in the car is the charged power on the battery.

If you AC charge you can check this by having a kWh counter on your main fuse. You will then know how (in)effcient your on board AC/DC charger is. Am I wrong?

 

[wndrful]

SQLCPH testcase: 59KWh is the actual power that went in. Display on the left corner shows the DC power numbers (when display is in % battery)
You can figure it out the efficiency as follows:
Look at the charging screen anytime during mid-charging.
1. AC power = volts * ampere (right corner; this comes from your charging setup)
2. DC power = shown in left corner; shown in KW when display is in % battery)

In my charging scenario (240V/40A): there is ~92% efficiency; DC Power/AC Power = 0.92

Nice. Thanks SQLCPH.

I still have to check on mine. Car in shop for 12v replacement.

 

[wk057]

I'd be willing to bet a good amount that the 70 pack is a 14 module pack using the same modules as the 85. This would give them the ability to tighten the SoC window a little more in favor of battery longevity due to the "extra" 4kWh in this setup. Would allow slightly higher overall operating voltage as well vs the 60 which would lead to lower current draw and thus higher efficiency.

Added benefit is eliminating the 60 type modules for production efficiency.

Looks like the voltages in this supercharging 70D pic from another thread would pretty much confirm my hypothesis. Same voltages as the 60 pack, so still 14 modules.

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