PV Gap

Mario Said:

Type and size of capacitor needed for a solar project?

We Answered:

I don't know what your budget is or what your current requirement is. The cheapest large- capacitance capacitor is the electrolytic type, but it is usually (charge) leaky. Tantalums are not as large capacitance and are more expensive, but are not nearly as leaky.

You'll have to compare prices to see if it's cheaper to buy one big capacitor or build a bank of smaller ones. If money is no object, then you might check out the new super (or ultra) capacitor which can be used instead of a battery in some appliances.

To figure out the charge you need to store, multiply the max. USB current (A) you need by the time (s) it takes to power the USB (or the max time your solar cell may be down, whichever is less). Then divide that charge by the supply voltage (V) to get capacitance (F) (C= Q/V = I*T/V). For safety, I'd also get a capacitor rated at least twice the supply voltage.