Capacitors can be wired in parallel for higher total capacitance and lower total ESR.
What are some practical constraints/pointers for using many parallel capacitors (for example, 10, 25, 50, or 100)?
Application example: using 30 330 µF aluminum polymer capacitors to replace two 5000 µF wet electrolytic ones inside devices intended for long-life at low-variance operating temperatures (for example, illuminated ocean buoy).
As DKNguyen pointed out it is important to "account for" or "manage" failures. We put capacitor banks on the 28 VDC power bus of spacecraft all the time. EVERY cap had its own fuse, so if the cap shorted out - which was the predominant failure mode - the fuse would blow and take the cap out of the circuit. We were also concerned about partial shorts of a cap, so we broke the entire bank into 2, 3, or 4 sections and each section was fed with a relay so that we could disable that section of the cap bank if there was a partial short. If you can , use a cap that has detailed specs on internal resistance and inductance and make a model on Spice (I use LT Spice) and check out the response across a wide frequency range - maybe up to 10 MHz.
Thanks !!
Fusing is good, as stated by xstack. Ripple current sharing can be an issue when AC currents are high and tracks are long. Equalising trace impedances is good practise here. Thermal stability should be considered, so the capacitors should be at a relatively even temperature part of the product enclosure.
If, say, one capacitor out of a parallel group of eight was near some hot choke and its ESR fell then it would hog the ripple current and die young.
Any capacitor turning into a dead short for any reason will have access to all the short circuit current of all the other capacitors combined. Which can lead to something that could be described as either a self repair mechanism (the shorted capacitor will be demolished and neutralized quickly) or self destruct mechanism (so will anything near it). Cascade failure is theoretically possible (if another capacitor is shorted due to the damage).
