Tesla’s promises don’t compute with current physics and economics of batteries

Post by petre » Sat, Nov 25, 2017, 7:01 AM UTC

baddox wrote: post #48

nimos wrote: post #30

The Tesla superchargers currently charge at around 2% a minute up until about 80% which is 40 minutes to hit 80%. Tesla is advertising 400 miles in 30 minutes which is 80% of the 500 mile capacity. What is so hard to believe about a 33% improvement over a couple year old tech that is a couple years from release? Here are current industrial/transportation/residential electric prices in US [0]. They think Tesla will pa…

All these EVs use roughly the same small cells, right? Essentially thousands of the same cells used in hobbyist RC aircraft (with which I’m fairly familiar)? Unless I’m mistaken, each little cell should theoretically be chargeable in parallel, limited only by heat, massively parallel wiring, and the one massive input carrying ridiculous current. In theory, if one cell takes 30 minutes to charge, all cells could be ch…

Post by petre » Sat, Nov 25, 2017, 7:06 AM UTC

kumarvvr wrote: post #56

baddox wrote: post #48

Earlier quoted context omitted.

All these EVs use roughly the same small cells, right? Essentially thousands of the same cells used in hobbyist RC aircraft (with which I’m fairly familiar)? Unless I’m mistaken, each little cell should theoretically be chargeable in parallel, limited only by heat, massively parallel wiring, and the one massive input carrying ridiculous current. In theory, if one cell takes 30 minutes to charge, all cells could be ch…

If all of them are connected in parallel, then you are right. It's like filling an array of glasses in the rain. However the superchargers connect to the vehicle through a power port, which is relatively small. So it may not have as many parallel connections. You could split the charging to individual cells inside the car, allowing for parallel charging of all the cells simultaneously, but that means that the superch…

Post by petre » Sat, Nov 25, 2017, 7:13 AM UTC

kumarvvr wrote: post #65

cperciva wrote: post #55

Earlier quoted context omitted.

My point is that having a larger capacity battery automatically increases the wattage at which you can recharge. It's not like a gas tank where a 100L tank takes longer to refill than a 50L tank.

No, capacity of the battery isn't what determines the wattage at which you can recharge. It's the physical power supply constraints. If I have a 250v, 25 kWh battery, I can charge it at 250 V, 100 Amps for 1 hour or at 250V, 1000 Amps for 6 minutes. What charging rate I select depends on the voltage and chemistry in the battery. Can the battery support charging at such a rate. The charging current rate is limited to…

Post by erikpukinskis » Sat, Nov 25, 2017, 7:15 AM UTC

flor1s wrote: post #17

mtgx wrote: post #12

Earlier quoted context omitted.

Bingo. Not only that, but they may even rely on battery extrapolations for 2022, despite the truck and car being launched in 2019-2020. All they need is to break-even in the first year or two, and then they can make-up the profits from the improvement in battery prices. That said, the roadster itself will likely be profitable from day one. It's the truck that may not be. This is why Musk keeps getting ahead of everyo…

Meh, I think other companies just don't have the bravoure a man like Musk has. Also it helps if your company is a start-up and no heads will roll if you don't make a profit. Established companies don't have that luxury.

Post by sametmax » Sat, Nov 25, 2017, 7:27 AM UTC

nimos wrote: post #30

The Tesla superchargers currently charge at around 2% a minute up until about 80% which is 40 minutes to hit 80%. Tesla is advertising 400 miles in 30 minutes which is 80% of the 500 mile capacity. What is so hard to believe about a 33% improvement over a couple year old tech that is a couple years from release? Here are current industrial/transportation/residential electric prices in US [0]. They think Tesla will pa…