Super capacity balancing boards for solar panel


Thread Starter


I'm using a super capacitor with a solar panel to keep the panel voltage around its Vmp. Nothing fancy just something like this:

In case someone doesn't know what these boards do, they balance the caps to an equal voltage and cap the voltage to a max of 2.7v per cap. If you attach an 18V power source, the excess voltage will be dissipated as heat by the balancing board.

Now, the total voltage of this board is 6*2.7v = 16.2v. So if the panel has a Vmp of about 18v and charges the cap to 16.2v, we'll be pretty close. Attaching a step-down buck converter to the cap at that point would give me close to the max power from the panel at the voltage I desire.

But I'm considering how I could target 18v which is the sweet spot. It's a 10% increase in power.

Unfortunately it is simply not possible to buy balancing boards with for example 7 super capacitors on it. 7 is better than 6, since 7*2.7v = 18.9v but those boards simply don't exist. I'm not sure why a cluster of 6 caps is so universally used, but they are.

So I'm thinking, fine, I'll buy another one, and then simply desolder 5 of the 6 caps on the second board. I'm just not sure if this will work as intended. How will the balancing circuit on the second board react to the missing 5 caps? Will the total voltage of the two balancing boards wired in series really end up around 18.9v? Will the second board dissipate excessive voltage as it was designed to do with all 6 caps mounted?

Mike Stevens

It appears that the intended market for these series-connected 2.7 V super-capacitors is automobiles, specifically connecting the string of six series-connected capacitors in parallel with a standard lead-acid "12 V" battery, which has six cells with a nominal 2 V per cell. The automobile alternator charging system will produce about 13 to14 V DC to keep the lead-acid battery charged, which is a good match to 2.7 x 6 = 16.2 V maximum voltage that should be applied to the series-connected super-caps. If you look closely at the circuit board to which the super-caps are connected, each charge-balancing circuit is connected in series with the adjacent charge-balancing circuit by means of a multiplicity of plated-through holes to ensure a good current distribution when the series string is discharged at high current levels, presumably while starting the engine. I see no reason why you couldn't continue this connection scheme to make a longer series string of super-caps to match the maximum power point voltage of your solar array.

You could remove the extra super-caps for use as replacement spares.