4 ms·
They achieve this by "charging cable that can deliver a current 4.6 times that of the fastest available EV chargers". However, that also means 4.6^2 = 21 times
by iliketrains 5y ago
They achieve this by "charging cable that can deliver a current 4.6 times that of the fastest available EV chargers".
However, that also means 4.6^2 = 21 times more losses in the transfer cable since losses are P = I × V = I² × R (where P are losses, I is current, V is voltage, and R is resistance of the cable).
Wouldn't be better to increase voltage? I guess that would require changes to cars?
- fzzzy 5y agoYes, it would be better to increase the voltage. But R also decreases as temperature decreases.
- framecowbird 5y agoAre the losses significant on such a short cable?
- pengaru 5y agoThe cables are already liquid cooled apparently, does that answer your question?
- framecowbird 5y agoThe parent comment said that the losses would be 21 times higher. My thought was, surely the losses on a short, liquid cooled cable were pretty negligible to begin with..
- Rexxar 5y agoWho says R is the same in the new cable ? Additionally, your demonstration is incorrect, with the same argument you can also write P = I×V = V²/R and conclude that you don't want to increase voltage.
- nitrogen 5y agoThe V in that equation is for voltage drop along the cable, though, not total system voltage relative to ground. And that voltage drop is proportional to total system current, but not total system voltage.
- kens 5y agoYou're mixing up the supply voltage and the voltage drop in the wire. Increasing the supply voltage will decrease the voltage drop in the wire (assuming appropriate adjustments to the load). It's the same reason you're better off using an AC extension cord for your phone charger than using a long USB cable.
- SigmundA 5y agoEV chargers and cars are already up to 800 volts, to charge a 100 kWh pack in 5 minutes you need 1.2 megawatts which is 1500 amps. Chargers and batteries might go up to 1000v but don’t think there are plans to go beyond that at this point.
- bryanlarsen 5y agoThe proposed Megawatt Charging System for class 6-8 trucks supports up to 3000A and 1500V.
- SigmundA 5y agoI stand corrected, I thought HPCVC was 1000v at 3000 amps for 3 megawatts. However it looks to be 1500v at 2000amps to do 3MW.
- bryanlarsen 5y agoSo did i until I looked it up. perhaps it changed recently.
- rektide 5y agoIt actually would be pretty brilliant to put a 4~20kV+ SiC buck converter at the end of a cable, drop down to target voltage at the end, given how vicious power losses in a cable are & how bloody efficient SiC buck converters are. Still, getting enough output current is going to be hard. Even 750A (10 minute charge) is going to be rough. GeneSic makes some 3.3kV to247 mosfets that can do 200a, about $300 a pop on mouser. And even at better than the best efficiency that charger head would require really good active cooling, probably water cooled. Still i like the idea of staying ultra high voltage till the very end.
- rini17 5y agoEnd of the cable isn't the best place, you will still need a connector capable to handle gazillion amps and also solid hunks of copper inside car to connect it to battery. Better to integrate it directly into battery packs.