It's the i3's turn to get our DC fast-charge test
As we continue to get new electric vehicles to test, we decided we need more exclusive and educational content for current and future EV owners. In addition to our 70-mph highway range tests, we're also conducting DC fast charge tests on all of the new EVs that we get on media loan.
When we cannot get a media loaner, we often borrow a vehicle from a dealership or a friend, as was the case with the 2020 BMW i3s I recently used for a 70-mph highway range test and this charging test. My friend and EV aficionado, Chris Neff was kind enough to allow me to use his car for the range and charging tests.
Most people understand that EV range varies widely from vehicle to vehicle. However, many people, especially those new to EVs don't know a whole lot about charging them. Unlike ICE cars the refueling process can vary greatly from EV to EV because electric vehicles charge at different speeds. More specifically, they have different charging curves, and there are many factors involved in how fast they charge.
We drove the i3s REx down to 6% state of charge so the range extender would turn on. That way we knew the battery is as low as we could get it for the test. We would have preferred using a 2020 i3s BEV so we could drive it down to zero, but we couldn't secure one for the test.
The BMW i3 is capable of accepting up to 50 kW of power, and BMW claims a recharge time of 40 minutes when charging on a 50 kW or greater DC fast charger. We used a 150 kW unit on the Electrify America network, so power delivery wouldn't be an issue.
Immediately upon plugging in, the i3 accepted 42 kW, which was a good sign. During the charging session, the i3 slowly increased the charging rate all the way up to 48 kW. In fact, the i3 never slowed down the charging rate, it just kept climbing the entire time.
While the i3 never reached the 50 kW maximum charge rate advertised, it did charge to 80% in under 40 minutes (2 seconds less!) than BMW claims it will. I believe the reason it didn't start out at a higher charging rate was that the battery wasn't warm enough plus the fact that the pack voltage is lower when the state of charge is low, resulting in a slightly lower maximum draw.
The vehicle was parked outside overnight in 50-degree (10° to 12° C) temperatures, so although it came close, it wasn't able to accept the full 50 kW. That's why the charge rate gradually increased; because the battery temperature was going up.
While the i3 can only charge at 50 kW, the charging curve is great, and the vehicle doesn't even start ramping down the power it accepts until it reaches about 86% state of charge, according to Fastned.
While the i3 is limited to only accepting only 50 kW on a DC fast charger, future BMW EVs will charge at much higher rates. The 2021 BMW iX3 for instance, can accept 150 kW and BMW has indicated in the past that they recognize the importance of fast charging, especially with EVs that have large batteries. Therefore, we don't expect to see a 50 kW limit in future models from Munich. We also hope they continue to offer robust charging curves, but that becomes more challenging as the maximum power increases.