Comment by pornel | Hacker News Reader

Comment by pornel | Hacker News Reader

All the retrofits I've seen only have AC charging. Is there a reason why they don't support DC charging, even at lower power if necessary?

Generally speaking since DC charging is so fast, you need to have very tight control over the cooling and performance of the cells or you’ll have issues with longevity. Lots of retrofits just kind of stuff batteries wherever they fit… so cooling isn’t going to be the most effective. By comparison, AC charging, even at 12kW, is quite slow for a decent sized battery pack.

I don’t think there’s any technical/protocol reason you couldn’t do this, it just complicates things quite a bit.

I have built multiple EV conversions and used DC charging.

- AC is easier to start with

- DC charging protocols you need to communicate & negotiate with the rapid charger in the street

- There is no reason why you couldn't DC charge any conversion in principle, just comes down to time & effort

If you want to read more, AC is J1772 and is just a voltage dividing resistor with some PWM https://www.fveaa.org/fb/J1772_386.pdf

For DC there are two (three?) protocols

- ChaDeMo is being phased out despite being the best one (V2G & simplicity of use)

- CCS2 is what the big manufacturers have come up with and it is hilariously complicated. My friend Uwe developed the FOCCCI project that has reverse engineered it

- In the US Tesla are using NACS (not sure on the details)

I am recording a video series where I illuminate the tech behind EVs, charging and energy, you can find it in my submissions.

NACS uses the CCS protocol, which makes dumb adapters possible.

There's more complicated software involved in DC charging due to the much higher power levels, plus more complicated monitoring of the system. AC charging is much more straight forward and simple.

In other words, cost is the issue here. If you have a large budget, you can get the best components. But with a lot of conversions, the whole point is giving a second life to an otherwise relatively worthless car and avoiding the larger expense of getting a proper EV. It doesn't make sense to get tens of thousands of dollars worth of components for that. Simple, easy, and cheap is the whole goal here.

There are some nice conversion kits for things like classic cars where it makes sense to have fast charging. But then we're talking 50-60k in cost and a lot of labor. For that kind of money, you can get several decent second hand EVs or even a new one. Spending that kind of money is only interesting because it's a classic car. E.g. a lot of old porsches apparently drive a lot nicer and better after an EV conversion. Also not having them break down with weird mechanical issues all the time makes driving them more fun. Also, more torque, power, etc.

But you wouldn't do that with some generic consumer car where the whole point of the conversion is avoiding the expense of buying a proper EV. You can get some nice used EVs for under 10K now. Pretty decent ones even.

Several reasons: because AC charging is what people will generally have at their house, so if you only have one charging system that's the one you'd probably go with. Because there are several pretty good AC charging system that are sold to the DIY conversion market. And because EV conversions often run at relatively low voltages compared to OEM vehicles, and DC charge stations generally have a minimum voltage they're willing to charge, which I think is usually somewhere around 400 volts or so.

Large cities in countries where many people can't afford cars, and there's little mass transit, will be more compact. No driving 10 miles to the mall like the USA. Shorter distances, less need for huge battery packs, or the latest technology. Most AC parts can be had off the shelf.

Putting DC charging in an EV is like putting a turbo in a gas car. You can do it, but it'll be expensive and complicated, and you probably don't need it.

Well that’s not really how it works. Even with 22 kW AC (what is rare in Europe) Tesla model Y needs 4 hours to charge from empty to road ready. And it is show stopper, because any petrol car needs 5 minutes to go another 300-600 miles. With DC charger I can have a normal break of 40 minutes and have enough charge for another 300 miles. DC charging is the topic to ease range anxiety and make EVs viable replacement for petrol cars. Without gooood DC charging capability the electric cars are suitable as city cars at best.

Edit: model Y does not support 22 kW AC charging. Only 11 kW AC. And it still takes whole day to fully charge.

The point is that maybe most(some?) people don't need DC charging at all. I've owned our VW e-Up for 3 years now, drive it literally every day, and I never needed to fast charge it because I've not once taken it on a trip longer than its battery range. I just never had a need. In fact I'm just charging it from a normal domestic socket at a meagre 2kW once a week and that's absolutely enough. Obviously it won't work for everyone, but I bet it would work for a whole range of people - some of my friends have definitely never driven more than 100 miles in a day in their cars and they lug around 50 litres of petrol in their tanks "just in case".

I don't know many cities which would challenge a 400km EV range, actually with that range I'm already across the border in any direction I'd drive. But okay I'm one of the dozen or so people who don't live in the US.

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