Fast EV Charging: Lessons Learned

A recent trip to Palm Desert from San Diego, in my relatively new Nissan Leaf EV (her name is Wanda), gave me some new insights on EV driving and charging. In particular, Fast Charging.

Charging in general isn’t quite as easy and straight forward as I originally thought. Wanda is my second EV. My first EV, Clara, had a range of about 90 miles. Wanda has a range of about 160 miles, but as EV drivers learn, ranges are highly dependent on terrain, temperature, AC usage and driving style. Even though the trip was only 138 miles, we knew that we wouldn’t quite make it without charging. So, we carefully planned to make a stop at a Fast Charger about midway. From previous experience using Fast Chargers, 30 minutes provides about a 60% charge. Ready to go, we noted the range was 145 miles and Wanda had a 98% charge. We drove conservatively just in case we used more power than expected. The charging location was 60 miles away, but there were only 44 miles left in the estimated range when we arrived, and the temperature was about 95 degrees. We stopped for about an hour, but for some reason the charging stopped after 30 minutes. We assumed it was an issue with the charging station, and since we had plenty of power to get to our destination, we didn’t give it much thought.

Palm Desert temperatures ranged between 85 and 112 degrees over the weekend, and we had so much fun that we forgot to plug Wanda in the night before we left. Although not fully charged, we had enough power to drive to a nearby shopping center with a Fast Charger. We estimated we could shop for an hour and be set for the drive home, however after an hour, the charger stopped charging even though Wanda was only 50% charged. Frustrated, because we weren’t notified, we started the charger again. After another hour, Wanda received more of a charge but was still not fully charged. After another 20 minutes, she was 98% charged and we were finally on our way. We didn’t get very far before a warning light and cute little turtle popped up on Wanda’s dash to indicate that speed would be impaired and that we should stop and cool down. 

A pitstop in the shade gave us time to contemplate what had happened. We figured out that the multiple Fast Charging sessions, coupled with the external heat, was the main cause for the overheated battery. The short breather made the little turtle disappear and enabled us to get back on the road. We made it home and certainly learned much about EVs, batteries and Wanda’s other display features that we had never looked at before like her battery temperature. She was quite happy to be back home in San Diego’s cooler evening temperatures.

Further research on Fast Charging confirmed our thought that a rise in battery temperature stops charging before finishing a charge. The 111-degree heat certainly didn’t help our situation. Extreme temperatures, hot or cold, also reduces the speed that the battery charges. Interestingly, there are also many articles and discussions that indicate higher battery degradation and shortened battery life are associated with using Fast Charging. In summary, the lessons learned were: 1) while convenient, reconsider using Fast Charging stations on a regular basis, 2) don’t depend only on using Fast Charging on a trip or 3) just slow down and relax, the destination will still be there a few hours later. In any case, Wanda will be quite happy to stay home for future desert or long trips.