3 ms·

This is one reason I'm hoping that lithium iron phosphate batteries catch on for the low-to-medium end EVs that don't need huge range, as the batteries tend to

by elihu 5y ago

This is one reason I'm hoping that lithium iron phosphate batteries catch on for the low-to-medium end EVs that don't need huge range, as the batteries tend to be quite a bit safer. Not that it's impossible to catch LFP cells on fire, it's just harder. I also wonder if it would help to have an emergency discharge port or something? In other words, a fire truck pulls up and they plug a cable from the car's discharge port that energizes some high-power heating elements to boil water or something. The idea being that the faster you can discharge the battery, the less stored energy you have to deal with catching things on fire again. (Though it might not actually help, since in the short term extracting power from the battery will just cause it to heat up more.) (The "emergency discharge port" could just be a DC fast charger port with some method to force the contactors to engage.)

elihu 5y ago
...another variation on this would be an emergency water cooling port. Like you have a fixture somewhere on the car that you can connect a hose to and it runs water through coolant channels. A lot of EV batteries have something like this already, you'd just have the ability to run external water through it instead of just going with a closed loop. You'd also need an outlet, which I guess would spill ethylene glycol all over everything if it wasn't contained, but better that than a burning car.
- sokoloff 5y ago
  Many race cars are plumbed with a port that can take pressurized water into the cooling system from the pits, and already have a temp/pressure valve to vent excess pressurized coolant [water in the case of a racecar, coolant mix for a road car] so the tech exists.
clomond 5y ago
Well good news: LFP is likely to become the dominant chemistry in most transport applications that don’t have specific or very high capacity energy weight/volume density requirements, the lower end of EVs and passenger vehicles included. LFPs I expect will slowly eat up the higher end of the market as it specifically improves and scales. Issues with the discharge port I can see include the issues that: - broken circuit means energy will struggle to get anywhere even if you wanted. Solving for this increases complexity substantially and non-linearly. - maximum discharge rate of the cells could mean even at max output it could take well over 10 minutes to depower if not much longer (and discharge also has a trade off of them heating up accordingly at higher discharge rates) Ultimately, you have a lot of embodied “loose” energy and once the reaction has left your control and the walls of the cell are breached (and enough of them), it’s more akin to a collection of little firecrackers that “combust” when they touch each other rather than a fire that can be “extinguished”. Just in slow motions because they are metals.
sanarothe 5y ago
I always liked the chemical acronym LiFePO4... it has "life" right in the name!

by elihu 5y ago

elihu 5y ago

...another variation on this would be an emergency water cooling port. Like you have a fixture somewhere on the car that you can connect a hose to and it runs water through coolant channels. A lot of EV batteries have something like this already, you'd just have the ability to run external water through it instead of just going with a closed loop. You'd also need an outlet, which I guess would spill ethylene glycol all over everything if it wasn't contained, but better that than a burning car.

sokoloff 5y ago
Many race cars are plumbed with a port that can take pressurized water into the cooling system from the pits, and already have a temp/pressure valve to vent excess pressurized coolant [water in the case of a racecar, coolant mix for a road car] so the tech exists.

clomond 5y ago

Well good news: LFP is likely to become the dominant chemistry in most transport applications that don’t have specific or very high capacity energy weight/volume density requirements, the lower end of EVs and passenger vehicles included. LFPs I expect will slowly eat up the higher end of the market as it specifically improves and scales. Issues with the discharge port I can see include the issues that: - broken circuit means energy will struggle to get anywhere even if you wanted. Solving for this increases complexity substantially and non-linearly. - maximum discharge rate of the cells could mean even at max output it could take well over 10 minutes to depower if not much longer (and discharge also has a trade off of them heating up accordingly at higher discharge rates) Ultimately, you have a lot of embodied “loose” energy and once the reaction has left your control and the walls of the cell are breached (and enough of them), it’s more akin to a collection of little firecrackers that “combust” when they touch each other rather than a fire that can be “extinguished”. Just in slow motions because they are metals.

sanarothe 5y ago

I always liked the chemical acronym LiFePO4... it has "life" right in the name!