+1 for battery university, they're an excellent source. Does anyone have any other suggestions for similarly technically deep (while approachable) articles on any other facet consumer electronics?
My understanding from this article is that:
1. Charge the battery to as low a max percentage as possible (till about 65%) 2. Keep it as cool as possible (up to zero degrees C at least) 3. Use it as little as possible before recharging it (minimize charge-discharge bandwidth)
Aka, over-rate and over size the battery if you're building the device, and minimize extremes on any side of soc (state of charge).
Do EV manufacturers use any other tricks not covered by this?
(Of course, use the device as needed, these are just guidelines for the best perfomance.)
I don't think this advice is useful. You're going to use your devices, so you won't control the temperature or, largely, the charge percentage.
I think good advice is to keep your devices as cool as you can (ie don't leave your cars in sunlight when there's shade), which you probably did anyway, and keep the battery between 20% and 80% as much as possible. If the battery is going to stay unused for a while, leave it at 3.8V (or close to it), or at 50%.
Batteries are ultimately consumables, so don't stress too much. Just care for them as much as convenient, and that's it.
Light bulbs (including LEDs) are similar. If you use them at slightly lower then their maximum rating, things tend to last a LOT longer. The "Dubai lamp" uses this concept - oversized LEDs that are derated, and last a very long time (100k hours). You can do the same by buying oversized dimmable LEDs and simply turning down the brightness.
> Do EV manufacturers use any other tricks not covered by this?
Automotive EE here. EV aren’t ready for world wide use. That statement is constantly ignored by people in California who see zero issues with their new expensive fancy cars.
Shortest version… The heating and cooling systems of the battery are there to prevent damage. BUT… who powers the heating and cooling systems? The battery of course.
In a traditional or better yet a plugin hybrid, you can use the gas engine to control how much electric you are using in conditions that would be harmful to the battery. In EV vehicles you have no choice. The car won’t tell you “you can’t drive right now”.
The marketing of EVs was a mistake, and every mfg is paying for it. Ford taking a 2 billion write off this year on their EV line and canceling a lot of their vehicles.
They will be cool, but this generation makes a great second vehicle or town vehicle. Absolutely not an extreme weather highway vehicle.
Degradation is driven by many things, but a big one is heat. Elevated temperatures during both charge and discharge is very bad for battery longevity. To manage this, almost all EVs use liquid cooling, with a cold plate directly contacting as many battery cells as they can to move heat out of the battery. This coolant is then cooled by a radiator, an AC chiller, or both.
The worst temperature abuse case is DC fast charging, aka Supercharging, where high current charging creates tons of heat due to resistive losses. This is why frequent fast charging causes faster battery degradation, but ordinary charging and driving does not, because the coolant loop is sized for the DC fast charge heat transfer requirements.
Besides removing heat, adding heat into the system is also desirable. Cold weather environments approaching freezing or below is also bad for battery longevity, and more importantly, terrible for range. Resistive heaters are super power hungry, and to heat the battery coolant loop requires power from the battery. This is why, conventionally, EVs are terrible in cold weather.
> Do EV manufacturers use any other tricks not covered by this?
And now, onto the magic trick.
Heat management is so important to both the driving range and the longevity of a vehicle that EVs have moved from traditional resistive heaters to heat pumps. These magical thermodynamic devices can move heat from anywhere, including drawing heat out of cold ambient air.
When you combine that with a valve design that allows the heat pump to access the battery coolant loop, the motor drivetrain coolant loop, the cabin coolant loop, the vehicle computer(s) coolant loops, and external ambient temperature, you can have a super efficient system that shuffles heat where it's "wasted" to where it's "needed".
Tesla has an excellent video briefly covering their heat pump and their very clever Octovalve design: https://www.youtube.com/watch?v=DyGgrkeds5U
For more depth, this video covers the heat pump and the ~22 different sources of heat it can draw heat from: https://www.youtube.com/watch?v=Dujr3DRkpDU