Which takes less time to recharge from empty?
A car with a 50 KwHr battery, or one with a 100?
Ok, here's some data, based on 801 Tesla cars and their battery capacity. Full curves here: https://forum.abetterrouteplanner.com/blogs/entry/6-tesla-battery-charging-data-from-801-cars/
TL ; DR[th]Battery Code[/th]
[th]Tesla Model[/th]
[th]Estimated Usable Capacity[/th]
[th]10 kWh -> 50 kWh charge time[/th]
|
| BT37 | 3 Long Range | 72.8 kWh | 23 min |
| BT60 | S60 | 56.3 kWh | 42 min |
| BT70 | S70 | 65.7 kWh | 33 min |
| BT85 | S85 | 73.4 kWh | 27 min |
| BTX4 | S/X90 | 79.8 kWh | 23 min |
| BTX5 | S/X75 | 71.6 kWh | 27 min |
| BTX6 | S/X100 | 95.7 kWh | 20 min |
| BTX8 | Rare S/X75 | | 25 min |
So in this case they're not going to "full charge", they're seeing which batteries add 40 kWh fastest, going from 10->50.
As a general rule, larger batteries add 40 kWh faster than smaller batteries. There is some noise in the data because these are different battery configurations, and of course the Model 3 uses a completely different battery cell than the previous Model S/X.
But it's clear. Slowest is the [smallest] 56.3 kWh battery, next slowest is the [next smallest] 65.7 kWh battery, and the fastest is the [largest] 95.7 kWh battery.
Note: this analysis is somewhat skewed because this was before the 250 kW Superchargers had been released. These chargers were all limited to 120 kW.
The reason for this is that charge rate is dependent on battery size and on current state of charge.
Let's look at the charts for the second-smallest (they don't have a chart for the BT60) and the largest:
As you can see, the BT70 can take all the juice the 120 kW charger can give up until about 22% charge, or about 14.5 kWh of charge. After that point the maximum charge rate it will accept decreases. By the time you get to 50 kWh of charge (~76% charge, your charging power is only 40 kW.
The 95.7 kWh battery is able to charge at 120 kW charging power from about 13% (12.5 kWh of charge) up until somewhere in the high 40s percent charge, we'll estimate 47% (46kWh) from that red line, and then drops off very slowly until you get to around 58% (55.5 kWh).
Like the 65.7 kWh battery, charge rate drops off. The 40 kW charge power point for this larger battery is at say 91%, or 87 kWh...
So... The 95.7 kWh battery charges FASTER than the 65.7 kWh battery. Because it has more cells, it can accept more charging current for longer. And if you compare the curves, at any given state of charge measured in kWh rather than percent of charge, it will be charging at a FASTER rate.
Larger batteries charge at a faster rate than smaller. It's the nature of the technology.
