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the charging cycle of batteries is very slow compared to capacitors. Is it possible to use capacitors to quickly charge and discharge them to slow charge the batteries? For instance the range anxiety for electric vehicles could be minimized by shortening the battery charging times. Say charging 80% of the batteries in about 3 to 5 mins (like gasoline cars do) instead of 30 to 45 mins. If EV could do that instead of charging directly the batteries which a quick charger could take at least 30 minuetes, we could charge capacitors quickly and then they will discharge themselfs to slowly charge the batteries. Is it possible? is it feasable?

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closed as off-topic by ACuriousMind, HDE 226868, Kyle Kanos, Martin, John Rennie Aug 31 '15 at 14:42

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The question is more about battery chemistry than physics, but here are some things to keep in mind:

  1. Capacitors can typically retain MUCH less charge than a battery, since the latter stores energy in chemical form
  2. Supercapacitors are a class of capacitor that can be used for precisely the purpose you describe. From the Wiki page:

Supercapacitors are used in applications requiring many rapid charge/discharge cycles rather than long term compact energy storage: within cars, buses, trains, cranes and elevators, where they are used for regenerative braking, short-term energy storage or burst-mode power delivery.

Unfortunately they have much less power density than batteries - and while they have been getting better, so have batteries. If weight is not so important, but rapid charging is, they are indeed an excellent choice.

Usually you would not use the supercapacitor as a buffer between charging station and battery. The only exception I can think of is where you have a supercapacitor with extremely good short term storage (power density), but long term leakage. In such an instance, charging the SC quickly, then using it to charge a conventional battery more slowly, might make sense.

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  • $\begingroup$ Very clear answer. The supercapacitor with long term leakage is the answer I was looking for. Thanks. $\endgroup$ – J.Paps Aug 30 '15 at 19:39
  • $\begingroup$ @J.Paps - You may have missed the point that supercaps store much less energy (either from a volume or a weight viewpoint) than a battery, so charging a super cap, then using it to charge a battery, will require a physically very large cap. And if the supercap has a low leakage, you're better off getting rid of the battery entirely. $\endgroup$ – WhatRoughBeast Aug 30 '15 at 20:32
  • $\begingroup$ @WhatRoughBeast - you are right about the main point, but the "exception" in my last paragraph is talking about the possibility of using a small but leaky supercap that sacrificed leakage for size. $\endgroup$ – Floris Aug 30 '15 at 20:34
  • $\begingroup$ You are right about having a supercap between a charging station and the batteries. Why bother, besides supercap has a very low energy volume (wh/mass) compared to batteries. But what if technology could develop more quickly on supercapacitors than on batteries. I believe main problem on EVs is not how to gain watt hours per kg of energy storage. Main problem to solve on EVs is how to reduce charging times to compete with fosil fuels. $\endgroup$ – J.Paps Aug 31 '15 at 3:38

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