I have read that it is possible to directly connect a supercapacitor and battery in parallel due to lower inner resistance of the capacitor. This makes me wonder why are there little supercapacitors (only audio system caps) available in 12 V or 24 V? I can see why the voltage has to be somewhat low because of the thin dielectric, but with 2.5 V you need multiple and a balancing system too.
\$\begingroup\$
\$\endgroup\$
1
2 Answers
\$\begingroup\$
\$\endgroup\$
The double-layer effect that electrochemical supercaps use gives an exceptionally thin "dielectric" layer of <1nm which increases capacitance per plate area but reduces working voltage. It's harder to manipulate this layer to change working voltage than it is with standard caps (physically increase plate separation) or electrolytics (make the anodization layer deeper).
\$\begingroup\$
\$\endgroup\$
6
The cells are 2.5V (give or take). Anything rated more is either several in series and packaged as one unit (maybe with internal balancing, maybe none), or electrolytic (the 1F 16V "audio boost" capacitors are electrolytic, and much larger than a comparable value supercap).
You're probably looking for a bulkier adjective, like "array" or "module":
https://maxwell.com/products/ultracapacitors/modules/
answered Aug 6 at 16:11
-
\$\begingroup\$ I have seen the modules, but this increases complexity. My question is why are the capacitors not just offered in 12V (16.2V) per cap? \$\endgroup\$ Commented Aug 6 at 16:15
-
3\$\begingroup\$ No, there is no chemistry of a 12V supercap. You are looking for a module. Modules at these voltage levels are very reliable. \$\endgroup\$– TQQQCommented Aug 6 at 16:22
-
\$\begingroup\$ Maybe a better question is why did they settle on 2.5V per cap? \$\endgroup\$ Commented Aug 6 at 16:38
-
7\$\begingroup\$ @Sneaky_Krait That’s all that the electrode and electrolyte chemistry for double layer capacitors supports so far. If it was easy or economical to make them for higher voltages, they would do it. Wet electrolytic capacitors stop at 1000V for the same reason: we don’t quite know how to make them reliably for higher voltages yet. And even then 1000V electrolytics cost a fortune. The above limitations are active areas of research of course. So things will improve over time. \$\endgroup\$ Commented Aug 6 at 16:42
-
1
little supercapacitorandbig supercapacitor? Do you mean capacitance (e.g. 10 F, 400 mF) or physical dimensions? \$\endgroup\$