Largest 470,000uF (0.47F). In a big can with bolts for terminals. A snip at £125... each!!!
You can get non-polarised electrolytics, but they are less common & more expensive.
Posted by Dean_huster on Monday, 10 July, 2006 - 12:53 pm:
United Chemi-Con manufactures "ultra capacitors" up to 2700F in a single cell. These aren't the "toy" capacitors used by the idiots with the 1000W audio systems in their pocket rockets. These are industrial-grade. At those values, voltage ratings are typically around 2.5V, so the caps have to be "banked" in series/parallel to get higher voltage ratings for a given capacitance value. You can check them out at http://www.chemi-con.com.
Ceramic caps tend to have wild temperature coefficients, making them impossible for any circuits requiring a stable capacitance, such as timers, oscillators and filters. The only exception to this are NP0 (that's en-pea-zero, not en-pea-oh) ceramics, available in the small pF values and usually marked with a black swatch of paint on the top edge or the designation "NP0".
You'll notice that nearly all caps do not have the selection of values per decade that resistors do. While you have 24 values of 5% resistors per decade, you may have only six 5% caps per decade. This is because caps are typically used with resistors in circuits where cap value is critical. They work together to determine circuit operation, so it's more economical to select from a very few expensive caps and then vary the value of the cheap resistor to trim up the circuit parameters.