– 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.

Fundamentally, it could be designed the way you say. However, newer EV models are moving to the ‘skateboard’ platform where the battery is an integral and structural part of the car frame. At this point you’d have to basically make a car body that easily unbolts from the frame which would include the tires, brakes, etc. and it’s no longer practical.

Batteries are big and expensive, so it makes a battery swap station big and expensive. In addition they are all custom battery packs, so when going for a battery swap, you’d need to do it at a station that has your specific battery on hand.

Imagine if cell phones were like that, I have a Galaxy S7, I have to go to an S7 charge station, can’t use an iPhone charge station, can’t even use a S6 charge station. And then when my phone is too old, the charge stations will probably stop carrying my battery. So really, logistically, it’s a complete nightmare to do it.

Current batteries charge in 30-45 minutes, 10 minute charging is not too far off. And really, like your cell phone, how often do you really need to get it charged in 10 minutes? 95% of the time you plug it in when you go to bed, and it lasts as long as you stay awake. That other 5% of the time, you can take 15 minutes to charge it, and get an extra half charge, which will probably extend you as much as you need for the day.

Ev batteries are huge, and connected with high voltage cables and coolant tubes. It’s going to take as much time as changing the oil and rotating the tires. In that much time you can 75% charge a Tesla at a supercharger. Add in the time to drive to someplace with battery packs that cost $10k, which won’t be everywhere like gas stations or lube spots, think dealerships, and charging is quicker.

We could, but we don’t. Probably to ensure the battery is safe and safely attached. Another reason might be the fact that most consumers of electric vehicles don’t need such feature. If you are someone needs to drive way more than a full charge and speed charging, you probably are going to use a gasoline car.

But that doesn’t mean that we don’t do it all. Some warehouse vehicles have batteries that can be switched. Because in those environments it can be so busy that you can’t afford to leave a machine to recharge.

Nio did it, set up several stations and the result were that it’s quite popular for long distance driving.