Comment by numpad0 | Hacker News Reader

Comment by numpad0 | Hacker News Reader

Battery charging/discharging speed is limited not by capacity but by current relative to capacity. Li-ion batteries can generally be recharged in constant current mode without significant degrading up to "4C" - 4x its mAh rating, above a low threshold below which it's not yet safe to charge at full speed, and below ~80% where it's no longer safe to charge with constant current but charging has to switch to low current constant voltage mode.

Cutting down charging time to below 1/4th standard Earth hours require material science breakthroughs(hard). While this system might be useful for charging a 4MWh train packs, or a 1MWh semi pack with a not insignificant degradation penalty, this does not accelerate charging for most EV users even if this was to be deployed widely.

I think you jumped to the wrong conclusion. Another news source suggests proper groundbreaking 10C charging:for a standard EV

> the BYD’s pile supports the 10C charging. It can charge 400 km in 5 minutes. It is two kilometers in one second! During the live test, this station reached the 1 MW level of power in 10 seconds (while charging Han L EV and Tang L EV). The car’s charging time from 7% to 50% was just 4.5 minutes.

A nitpick on the math you cite: 400km in 5 min (300 sec) is not 2 km per sec.

The bigger open question is what is the degradation penalty for 10C charging. This doesn't matter for a demonstrator but is critical for consumer use.

Forget 4C, these have new 10C lithium iron phosphate batteries.

That's the thing, the manufacturer can rate the cells at any C they want. The real question isn't whether these are "rated" for 10C, but how much degregation these will show after 1000 cycles at 10C. Cooling systems will also play into this: If we assume 5% charging losses that's 50kW that will need to be dissipated while charging for the cells not to heat up - no small feat even if the losses are lower.

I think the real question is how is it degraded after 100/900 cycles of 0.2C/10C which is a normal charging pattern.

Reply on news.ycombinator.com