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User Info Is Tesla On The Verge of Bankruptcy?; entered at 2017-11-20 02:36:51
Gianmarko
Posts: 44
Registered: 2013-03-11 Bern, Switzerland
there are a couple things that really get on my nerves when discussing EV's.
first of all, all numbers and perf specs about EV's are overstated. a swiss magazine recently did a test of 3 EV's on the market, they did a pretty good and objective road test and real life ranges were 40% less of what the manufacturer said.
regarding the battery pak of the new roadster, the model S 85 kWh pack allegedly weight over half metric ton, and contains over 7000 cells. a 200kWh pack therefore would weight 1.2-1.5 metric tons. thats more or less the weight of my italian sportscar.
i use li-ion cells for my projects and i know them pretty well in real use. there is a ton of 'em with different specs and characteristics.
so first of all, the claimed simplicity of EV's (because there are very few parts" is BS. a battery pack is made out of thousands of cells, each one of them with its own balancing, isolating and protecting circuit. cells do fail and therefore you must expect the pack of your car to lose capacity with time and use.
secondly, cells lose capacity every charge-discharge cycle. the deeper the cycle, the higher the capacity loss. cell manufacturers publish this data and it is available online.
so each time you recharge the pack, you lose a little chunk of capacity, and this has a cost i never see published. in my calculations, the cost of this capacity loss in a deep cycle gets close to the cost of the equivalent amount of fuel before taxes. i have seen laptop battery packs that after couple years of light use lost 40-50% of the capacity.
thirdly, recharging the batteries.
lets imagine we have bought one of those shiny, fast roadsters with a 200kWh pack that we need to fully recharge, and lets assume some magician figures out how to build batteries that can be recharged at constant current in 6 minutes, just to use easy round numbers.
you will need a 2 GW (edit: 2MW) charger. thats a LOT of power. charging at 1000 volts, thats 2000 amps.
lemme tell you, i dont want to be nowhere near such operation and a problem in the cables, connectors, batteries, electronics will get you a firework you will remember for life
now, such magic battery could be produced right now utilizing the constant current part of the charging curve of a li-ion cell that can be charged at 2C, it would be heavy and expensive but is perfectly feasible, but the recharging problem is one of the various elephants in the room than everyone is trying to ignore.
i have a diesel car with a 70 liters tank. that, assuming 30% efficiency (which is a pretty realistic value) is the equivalent of a 220 kWh battery pack.
that is what you really need to have a decent range and a practical, usable car.
such battery cannot be recharged in 5 minutes, period.

EV's are an idiotic fad, produce of the sick mind of scammers and clueless central planners.

of course they will, at some stage, mandated, so nuking the economy in a single shot.


Last modified: 2017-11-20 08:56:56 by gianmarko
Reason: typo

2017-11-20 02:36:51