Featured Audi Shows That Its Fast Charging Curve Makes A Difference

when audi has a ton of 10 year old cars for real world degradation results, i'll become a believer

 

Audi is welcome to their beliefs but I do my own benchmarks:

In just over 13 minutes, I'll have 100 miles range. I only charge enough to reach my next SuperCharger with 30 miles reserve. In ~15 minutes, I'll have about 115-120 miles and 120 miles is the usual distance between SuperChargers in my area. My Std Rng Plus Model 3 fully meets my cross country requirements because I do not have to put an Audi sized charge each time.

Bob Wilson

 

Much of the reason why the E-tron can maintain high charging speeds nearly to 100% full, is that “100%” is really around 75-80%. The E-tron blocks out large top- and bottom-charging margins, and by some accounts, doesn’t use nearly half of its battery capacity.

That’s why, in “Elon numbers” the E-tron has a rather dreadful efficiency of ... 2.2 miles/KWh (IIRC). I say “Elon numbers” because he estimates that by dividing the range by the raw, physical capacity of the battery, rather than by the capacity actually used. In Elon’s defense though, Teslas reserve far smaller charging margins, and seem to be able to get away with those small margins, thus that is a pretty reasonable way to estimate their efficiency.

 

The reason this is a problem is that EVs use high-energy, low-power batteries. I own Lithium Ion batteries I can charge at 3C (equivalent to a 20 minute charge) from 0% to 95%, but they are around 30% lower in energy density (and 10 times higher in power density) than the batteries used in EVs. The batteries used in the Prius Prime are more similar to mine than to EV batteries and, in fact, they can be charged at 2C (like a 30 minute charge). This is because their greatly lower capacity means they have to have more power per unit of energy stored to push the car.

If a 100kWh Model S could charge like my batteries can, it could absorb 300kW continuously from 0% to 95%. Of course, it would only be a 70kWh Model S because of the 30% reduction in energy density, reducing that to 210kW unless the battery were physically bigger and heavier to compensate.

 

Audi shows the "competitors" going from initial charge rate up to a peak and back down to that initial charge rate in 17-18 minutes. Your charge shows your car doing that in 11 minutes, indicating your car isn't performing as well as Audi is claiming (yours is only able to exceed that initial charge rate for less time, while longer is better). So their claim seems to be generous towards the "competitors" if your car is to be used as a single example.

 

Sometimes it helps to see the numbers. So I tried to trace the curve scaled to the Audi chart and time:

• My 2019 Std Rng Plus Model 3 - peak 170 kW, the Dual Motor and Performance Model 3 peak at 250 kW
• Electric kWh needed:
  • 25 kWh/100 miles Std. Rng. Plus Model 3
  • 46 kWh/100 miles Audi e-tron

I'm less worried about the charge rate but more in how many miles I get per minute. The higher efficiency of pretty much every Tesla Model 3 means more charge miles per minute. The Audi has to wait longer at the charger to reach the distance the Tesla is already on the road.

Bob Wilson