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Battery Pack Charge via Supercapacitor

TheTalkingMule

Distributed Energy Enthusiast
Oct 20, 2012
9,158
43,608
Philadelphia, PA
I'm sure this noob question has been posed....but why can't standard lithium ion battery packs be charged via swappable supercapacitor(s)?

Say there were a handful of receptacles on the Model 3 that accepted supercapacitors and then somehow transferred their charge to the battery pack. Is that not a method of obtaining a small amount of range while driving?

Imagine ubiquitous supercaps with 4 miles of range. Would be super easy to supply and consume, the pack could be almost constantly charging and require much smaller packs.

Nuts?
 

TheTalkingMule

Distributed Energy Enthusiast
Oct 20, 2012
9,158
43,608
Philadelphia, PA
So you want to stop every few miles to get another little recharge? You want to have to physically remove and add Supercapacitors every few minutes? Just think of the infrastructure they would have to build. I'd say it is simply financially not feasible apart from not making sense ;)
I'd like to grab a set of capacitors the size of a six pack, throw them into an interior receptacle and have 24 miles of range transfer to my battery pack while I drive down the road. Obviously just a supplement to normal charging and supercharging.

The appeal of fuel cell cars is the "fueling" is theoretically instantaneous, you just need convenient swappable H vessels. This would be similar, but using only electrons.

From my 10 minutes of googling it looks like it's possible to charge batteries this way via some type of regulator, but how efficient would it be? How much battery charge can you get from a 16oz beer sized supercapacitor?
 

arg

Active Member
Supporting Member
Aug 22, 2012
1,838
1,853
Cambridge, UK
From my 10 minutes of googling it looks like it's possible to charge batteries this way via some type of regulator, but how efficient would it be?

Tolerably efficient - maybe 90%

How much battery charge can you get from a 16oz beer sized supercapacitor?

Assume your 16oz can is about 500ml volume. Here's some typical supercapacitors sold for transport applications:

ULTIMO Lithium Ion Capacitor Prismatic Cells | JSR Micro, Inc.

They claim 20Wh/litre, so 10Wh in your 16oz can. You'd need about 15 cans to drive the car a mile.

Supercapacitors are the opposite of what you want here - they offer extremely high charge/discharge rates and cycle life (in exchange for low capacity), while your suggestion involves slow discharge (as you've nowhere to put the charge apart from the conventional battery you assume is in the car), and not many cycles (you have to take them back to the shop), while you'd like large capacity.

Better would be to use ordinary batteries.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,845
9,870
Boise, ID
Thanks to @arg for the explanation. I'll just express a simple addition. Caps versus batteries just have different pros and cons. Caps have fast charge and discharge, but are low energy density. Batteries have slow charge and discharge, but high energy density.

So the point is, for the same amount of energy you are wanting to move around, the capacitors take up somewhere around 10 times as much space. They are really terrible for being portable if you are wanting to move a lot of energy. And please understand, the amount of energy to move a 5,000 pound car is a lot.

The caps in electric vehicles are only used in some specific types of situations, mainly buses. They drive about two blocks and stop to let people get on and off....over and over and over. So sure, with short drives and frequent stops, it's easy to put charging connections at some of the stops to just zap some energy into them very frequently in a few seconds. The bus doesn't need to hold very much energy at a time, so the large size of the capacitors isn't a problem.
 

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