I have a project that I need input on.

Is it possible to build a hybrid bank out of ultra-capacitors (UC) and batteries?

The generalized flow of the system I'm thinking is from solar (48V) to UCs (48V,) to batteries (48V,) then split simultaneously to an inverter for 120VAC and a step-down transformer for 12V.

Is it better to put the UCs before or after the batteries?

I'm purposely leaving out battery chemistries because I believe this concept is voltage agnostic. It shouldn't matter if it is lead acid, AGM, LiFePo, LTO, etc.

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    \$\begingroup\$ Sure it's possible, but what's the rationale for taking such an approach? \$\endgroup\$
    – jms
    Aug 28, 2021 at 18:21
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    \$\begingroup\$ Is it better to put the UCs before or after the batteries? ... from your description, there is no before or after \$\endgroup\$
    – jsotola
    Aug 28, 2021 at 18:35
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    \$\begingroup\$ It's better to leave the UCs out. \$\endgroup\$
    – Neil_UK
    Aug 28, 2021 at 19:32
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    \$\begingroup\$ Are there momentary surge currents you think will be beyond the capacity of the battery? Or are you just making "component salad"? \$\endgroup\$ Aug 28, 2021 at 21:15
  • \$\begingroup\$ Check the leakage current of the supercapacitors and calculate if that would hurt your system performance during a week of no sun. \$\endgroup\$
    – winny
    Jun 26, 2022 at 13:04

2 Answers 2


I would think that if the supercapacitor array is first in line and the battery banks after, sudden high amp drains can be serviced by the capacitor and the 'slower' amps from the batteries can recharge the capacitor giving a more even current and reducing battery wear.


There are hybrid supercapacitors to combine some of the advantages of both in one module.

But for a system with both battery and supercap a very a basic arrangement could be something like this: enter image description here

It is not optimal, the max voltages should match, etc. You could also separate them and put a buck-boost converter before or after each to manage different voltage levels. Or build some kind of charger manager to optimize the process in all cases.

I think that this kind of arrangements make sense in some cases. The supercap can prolonge the life of the batteries, can provide current surges if needed, help with short periods of low temperatures, etc. But you get also the disadvanges, leakage, enegy density, etc.


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