Group Actions
Engagement
  • Author Author: Former Member
  • Date Created: Date Created
  • Views 856 views
  • Likes 7 likes
  • Comments 3 comments
Related
Recommended

Modelling of Time Constants for Carbon Based Supercapacitors

Former Member
Former Member

Shameless plug to my recently published paper!  It's open source so you should be able to view it.

 

Key findings:

Supercapacitors do not behave like other capacitors (obvious if you've used one).  Mainly in that their charge profile is not linear due to an internal distribution of time constants.  This means that you can charge a SC up to 1V, say, for 1s, then go open circuit and the voltage will seemingly drop, or sag.  If you do the same test but hold the 1V charge for 2s the sag will be less.

Voltage sag

 

Conversely, and more importantly from a safety perspective, you can short out a SC, i.e. discharge it to 0V, leave it open circuit for a minute, and the voltage will have rebounded positively.  So that SC you thought was "flat" has seemingly recharged itself!  If you have a decent bank of these that could give you "a wee tingle" to quote Big Clive!  Interesting since there is no electrochemistry in a SC like there is in a battery.

Voltage rebound

 

What does this mean for us though?  Well as a researcher I am obviously very low in the TRLs so bear that in mind, but we actually know very little about how these devices actually work.  Modelling simulations that you may get in software may not be representative of real life (e.g. Matlab, LTSpice, etc).

Also, do not assume that the charge characteristics are linear, in that if your 5V SC is at 2V5 it is at 50% SoC.  It might be if you have held it at 2V5 for a long time (mins, hours, days, we don't know?) but certainly not if it has only just reached this voltage, unlike, say, a ceramic or electrolytic.

 

Food for thought, hope you find this an interesting insight to some of the work I am doing here at Loughborough University!

Parents

  • Searching the Internet for 'inherent time constant' (in electrolytic power caps) turns out to be a rather frustrating exercise - until one stumbles upon this post and reads the

    corresponding  paper that you co-authored. I hope you don't mind me bothering you with the subject more than three years later ?

    First of all I am curious if there has been follow-up research, at your university or elsewhere ?

    Furthermore I wonder, if similar phenomena and/or consequences have been established or could be predicted for parallel and/or series-connected electrolytic power caps ?

    (From a materials science point of view, high-tech electrolytic power caps could be considered the closest thing to supercaps i.m.o.).

    Looking forward to your reply, Ray

Comment

  • Searching the Internet for 'inherent time constant' (in electrolytic power caps) turns out to be a rather frustrating exercise - until one stumbles upon this post and reads the

    corresponding  paper that you co-authored. I hope you don't mind me bothering you with the subject more than three years later ?

    First of all I am curious if there has been follow-up research, at your university or elsewhere ?

    Furthermore I wonder, if similar phenomena and/or consequences have been established or could be predicted for parallel and/or series-connected electrolytic power caps ?

    (From a materials science point of view, high-tech electrolytic power caps could be considered the closest thing to supercaps i.m.o.).

    Looking forward to your reply, Ray

Children
No Data