– EV Battery Charging


Why can’t we keep battery stock at charging stations and replace the batteries in the car instead of waiting for the battery to charge? It would be much faster and many electric bikes and skateboards have this opportunity. I can understand that the current structure of the car might not allow but why is it not possible or if it is possible what is the issue being faced?

In: Engineering

Tesla did it, set up a station and the results were that nobody actually wanted it.

First, charging isn’t really a problem for EVs. You charge your car at night, every night, so typically you start the day at 100%. If you need to charge during a trip, you take a bathroom break and eat during the charging. So for the most part, it very rarely bothers people. If you’re commuting regularly and rarely do very long trips then the time when you wait for it to charge may be essentially never.

The second issue is that the battery is an important, expensive part of your car. And swapping your new, well cared for battery for one that may have been abused wouldn’t be a good tradeoff for a bit less waiting. People would need to be convinced that this downside is really worth it, and so far it seems they’re not buying it.

The second part may also set up some perverse incentives — the best time to swap your battery for somebody else’s is if you’ve abused your. And since you’re going to swap, there’s little incentive to take care of it. So a battery swap system may result in mostly abused and old batteries being swapped around.

It may be a better idea for some sort of industrial environment like delivery trucks, where there’s central management of a fleet of vehicles, and there are policies and monitoring, and consistent practices that ensure that the bad outcomes don’t happen. But you can’t do that with random people.

It would be possible, but EV batteries are much larger and heavier than bike or skateboard batteries. Because of size and weight, you’d need some pretty sturdy materials to fixate the battery on the car. This requires extra tools and takes time. Also, the car design would become far more difficult. In most cars that were actually designed as EV, the battery is spread out over the entire bottom of the car. This improves handling and stability. A replacable battery would have to be much more concentrated.

All that would only save you a few minutes of time too, as most recent EVs and chargers can get you a few 100 miles of range in 20-30 minutes and this technology is still improving. So while it’d be possible (and has been experimented with, I believe), it’s just nog worth it.

There have been companies that have tried this, like betterplace.

The reason it’s difficult is because manufacturers would have to agree on a standard battery format, batteries often have their own cooling system, which would have to be disconnected/connected, and anyone operating such a swapping station would have to have a stock of hundreds of thousands if not millions of dollars worth of batteries on hand.

It’s also a bit of a chicken and egg problem, because there’s no reason to build battery swapping stations if there are no compatible cars, and there’s no reason to build compatible cars if there are no battery swapping stations.

The battery weighs hundreds of kilos, is very large and is different in each model of electric car.

You’d need a car lift and a mechanic to unbolt it and put the charged one in, and that’s disregarding the fact you need to disconnect high voltage and cooling lines, so you’ll need to top off coolant in the car

But even if you manage that, you’d still need to charge them, keep track of which car model they go on and store them in some sort of warehouse because they are about the size of the wheelbase of the car

This was actually one of the design features of the Tesla cars. There was even a press conferance where this exact feature was being demonstrated hosted by Elon Musk. We do not know exactly why this have not been deployed. It does require a lot more infrastructure to be installed then just the chargers. This is also a lot of mechanical parts which may require more maintainence, especially when deployed outside in various weather. It would also require a completely different ownership model as car owners would be swapping out batteries all the time. There is also a question of how to handle damaged batteries in such a system. There is apparantly some reason why Tesla could not make this happen, they might not have been able to solve all the techincaly issues and even though it worked good enough for a demonstration it might not have been reliable in the real world with lots of dirt in various weather conditions and with worn parts.