Why is it necessary for Superchargers to 'taper off'...

Why is it necessary for Superchargers to 'taper off'...

just curious. Why can't the SC's pump juice at max input until its 95% and then taper off, versus the slow taper that gets 50% in 20 min, 80% in 40 min and 100% in 75 min?

ir | 20 juillet 2013

It's due to the battery. Imagine you are trying to inflate a deflated ball with a hand pump. At first it is easy going, the flat blob starts to take shape. When it starts to look like a ball, you feel some extra resistance. As you keep going, it gets harder and harder to squeeze more air into the ball. Eventually the pump seizes up and you cannot push any more air in. Keep forcing it and it will blow!

Batteries are the same, easy to fill when nearly empty. Near full, it gets harder to pack more energy into it. Keep going past full and it will catch fire and explode.

Anthony J. Parisio | 20 juillet 2013


Perfect description! | 20 juillet 2013

Tesla has also hinted that they may reduce the slow taper charging that occurs as it nears full to speed the charge. I think they have chosen to be very conservative to start and are still doing testing and analysis to see what can be done safely and without hurting longevity/life.

Kimscar | 20 juillet 2013

@ir has a nice analogy. A number of things happen as the battery take a charge. It's impedance goes up. More heat is being produced in the battery. To speed up the charge you have to increase the voltage. That will lead to more heat and age the battery. It would be nice to know how good the cooling is for the battery. Personally I would prefer to have the battery last longer.
Based on the roadsters batteries Tesla has a working formula as it stands.

Captain_Zap | 21 juillet 2013

I think of it like pouring water into a big glass. You start with a big slash of water but you have to slow down as you get to the top. If you want it to the very top you have to do it drip by drip.

Kimscar | 21 juillet 2013

If you want use analogies then @ir had a good one. Otherwise it's as stated above. The impedance (resistance of the battery) goes up with charge. To push the charge faster the voltage to the battery has to be raised to overcome the impedance. That will increase heat and put wear on the battery. Tesla has active cooling for the battery and whatever else they do that we don't know seems to work well with the present charge situation based on the Roadster battery life.

Brian H | 21 juillet 2013

I wonder how hard TM is trying to keep its battery tech secret. It does want to goose the EV market in general, and its biggest competitive advantage is the battery -- but is it trying 'all out' to defeat other mfrs.? It's a connumdedrum, or SLT.