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We're Charging Our Cars Wrong

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Re: We're Charging Our Cars Wrong

#51

Post by aorloff »

dhosek wrote: post #38
Elixir6419 wrote: post #10

It would be nice if instead of the fast charging problem the focus would be shifted to standardized battery packs, that can be field replaced. I don't really want to own 50-100kwh battery. I just want to use the charge in it and happy to pay for that.

I remember reading an article somewhere which explained why this was an impractical issue. I forget the details, but I think issues like weight, ending up with a battery pack that doesn’t hold its charge well, etc. were all big concerns. Weight seems like it would be a huge problem given that the battery is the largest component of the EV drive train and it’s usually kept along the floor of the EV for weight distribu…

CATL trying it supposedly next year with a rollout of swap stations

Re: We're Charging Our Cars Wrong

#52

Post by jmb99 »

metaphor wrote: post #9

Lightning strikes...how do EVs currently guard against it? - With galvanic isolation baked directly into onboard charger, I'm thinking worst case outcome is charging infra and isolation link get fried, but that really expensive EV battery remains safe. - Without galvanic isolation, battery goes...boom? Hopefully without you or your family waiting inside the vehicle under some false pretense of safety.

> Lightning strikes...how do EVs currently guard against it?

I mentioned further down-thread, but pretty much the same way everyone else does: don’t get hit by lightning, or have a lightning rod. A tiny transformer isn’t going to stop lightning, and it’s not supposed to.

Put another way, how do gas stations guard against lightning strikes? The concerns are roughly the same. The answer, in general, is “they don’t,” because they don’t need to.

Re: We're Charging Our Cars Wrong

#53

Post by nradov »

dhosek wrote: post #38
Elixir6419 wrote: post #10

It would be nice if instead of the fast charging problem the focus would be shifted to standardized battery packs, that can be field replaced. I don't really want to own 50-100kwh battery. I just want to use the charge in it and happy to pay for that.

I remember reading an article somewhere which explained why this was an impractical issue. I forget the details, but I think issues like weight, ending up with a battery pack that doesn’t hold its charge well, etc. were all big concerns. Weight seems like it would be a huge problem given that the battery is the largest component of the EV drive train and it’s usually kept along the floor of the EV for weight distribu…

Impractical? Nio is already doing battery swaps at scale in China.

https://hbr.org/2024/05/how-one-chinese-ev-company-made-batt...

Re: We're Charging Our Cars Wrong

#54

Post by tlb »

loeg wrote: post #28
cyberax wrote: post #21

So basically, remove isolation transformers, and feed the line voltage (7.2kV or so) through a simple buck converter into the car. Instead of galvanic isolation, use redundant ground connectors that are monitored for continuity. I'm not sure I agree with this. It puts too much responsibility onto the EVSE side, as it'll have to be able to break the fault if it happens. If something like emergency pyro disconnects are…

> as it'll have to be able to break the fault if it happens Are you talking about the case where both of the ground wires fail while charging? If either is non-functional when charging starts, it disallows charging. If one fails during charging, charging disconnects.

When a fault occurs (say a battery fluid leak to the chassis) and is detected, a mechanical relay has to open to disconnect the power from the grid. That can take 200 ms or so, which is a long time to have 400v flowing through you.

Re: We're Charging Our Cars Wrong

#55

Post by jychang »

irjustin wrote: post #46
Elixir6419 wrote: post #10

It would be nice if instead of the fast charging problem the focus would be shifted to standardized battery packs, that can be field replaced. I don't really want to own 50-100kwh battery. I just want to use the charge in it and happy to pay for that.

Realistically, this is a pipe dream. China has had a few that are trying this NIO being the most well known. To me, it's not really viable. The 3 main problems are - The extra costs in a vehicle to allow swapping within say 5 minutes is non-trivial. The physical space required to house X number of batteries ready, X number swap ready is a lot at any moderate volume. Last, Batteries are not universal and now you're co…

Would you do it if it was cheaper per kwh? Say you have an EV where any battery you get from the swap station is better than 90% degradation, and you pay $0.40 per kwh for the electricity in the battery- but you get the option to take a battery between 80% and 90% degradation, in which case you get the battery all filled up, but only pay $0.35 per kwh for the electricity in that battery.

Re: We're Charging Our Cars Wrong

#56

Post by starspangled »

ChuckMcM wrote: post #48
Elixir6419 wrote: post #10

It would be nice if instead of the fast charging problem the focus would be shifted to standardized battery packs, that can be field replaced. I don't really want to own 50-100kwh battery. I just want to use the charge in it and happy to pay for that.

Well it's patented and Tesla doesn't own the patent. But that aside, you trade a different set of problems, specifically what happens if the pack that is put into your car is damaged and as a result of that damage catches fire when it is discharging? That isn't something that happens with gasoline. I keep hoping flow batteries can overcome their issues as replacing depleted electrolyte with charged electrolyte is muc…

Contaminants in fuel can cause damage to cars. I don't know if retailers tend to carry insurance for this but typically they are responsible, although proving it may not be easy. I imagine the risk would be quite rare and fairly well handled with insurance.

What's patented? Seems like a ridiculous patent if it entirely covered all practical manner of swapping batteries to recharge an EV.

Re: We're Charging Our Cars Wrong

#57

Post by dboreham »

ChuckMcM wrote: post #48
Elixir6419 wrote: post #10

It would be nice if instead of the fast charging problem the focus would be shifted to standardized battery packs, that can be field replaced. I don't really want to own 50-100kwh battery. I just want to use the charge in it and happy to pay for that.

Well it's patented and Tesla doesn't own the patent. But that aside, you trade a different set of problems, specifically what happens if the pack that is put into your car is damaged and as a result of that damage catches fire when it is discharging? That isn't something that happens with gasoline. I keep hoping flow batteries can overcome their issues as replacing depleted electrolyte with charged electrolyte is muc…

A patent on the idea that a battery in something that uses a battery can be replaced has to be the world's most preposterous patent.

Re: We're Charging Our Cars Wrong

#58

Post by jjallen »

ChuckMcM wrote: post #48
Elixir6419 wrote: post #10

It would be nice if instead of the fast charging problem the focus would be shifted to standardized battery packs, that can be field replaced. I don't really want to own 50-100kwh battery. I just want to use the charge in it and happy to pay for that.

Well it's patented and Tesla doesn't own the patent. But that aside, you trade a different set of problems, specifically what happens if the pack that is put into your car is damaged and as a result of that damage catches fire when it is discharging? That isn't something that happens with gasoline. I keep hoping flow batteries can overcome their issues as replacing depleted electrolyte with charged electrolyte is muc…

Any gasoline can catch fire though, just like probably any battery can catch fire.

At some point we are going to have to stop comparing gas and electric cars.

Re: We're Charging Our Cars Wrong

#59

Post by mrheosuper »

So the problem is about preventing electric shock. Which is not a new problem at all.

Using galvanic isolation is 1 of the solution, but it's expensive. How about using something like RCB to detect mismatch between output current and input current. This is well tested after all

Re: We're Charging Our Cars Wrong

#60

Post by jmb99 »

coryrc wrote: post #30
tehjoker wrote: post #7

The argument sounds kind of persuasive to a layman (even one that did a little bit of EE a while back), but my gut says there would be no need to write this article if there weren't regulations or other engineering traditions that decided galvanic isolation is necessary for safety. I guess the difference is galvanic isolation is physically (i.e. passively) fail safe, while ground detection is an active safety measure…

We also require arc-fault breakers in the electrical code for new construction despite even their first-order effects being negative. We're drowning in over-regulation and the most prominent people pretending to care aren't going after the real problems.

Arc-fault protections are required primarily due to lobbying by receptacle and panel manufactures, not because they provide a real benefit. The number of people injured due to arc faults is vanishingly low, and a better solution to the majority of applications is to replace the NEMA 5-15 receptacle with almost literally any other (or at least improve upon the design). A more fitting comparison might be ground-fault circuit protections, which do very much have real benefits in all required situations without any drawbacks, while being very cheap to implement (effectively, a current clamp driving a relay).

On the other hand, feeding 7.2kV down a wire handled by very normal people in very normal (read: adverse; wet, humid, non-careful) conditions without any passive protections, relying on the portable (car) end to perform all of the shock safety is laughable at best. A bug in the car’s charging circuit (hardware, firmware, or software) and whoops, the chassis has 7200V to ground when the cable gets plugged in during a rainstorm.

Engineering safety regulations and guidelines are written in blood. Anyone who doesn’t understand that is either ignorant of the dangers involved, or narcissistic to the point of believing they are immune to danger.

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