While the ESU's Power Pack small keep-alive has been available for some years, ZIMO just came out with their miniature keep-alive. Unlike the small tantalum capacitor based (few thousand micro-Farads or less) modules , these are "real" Super Cap based keep-alive modules which store enough energy to keep an average N scale model running for couple of seconds.
Also unlike the physically larger Super Cap-based keep-alives from TCS which are simple circuits consisting of the caps, and couple of diodes and resistors, both the ESU and ZIMO keep-alives use fairly complex electronic DC/DC converter circuitry utilizing fewer low voltage rated Super Caps. It converts the standard 12V from the decoder to charge the much lower voltage caps, then when it needs to supply power during drop-outs, it converts the low voltage energy stored in the caps back to around 10V feeding back to decoder to keep the loco running.
Unlike the ESU Power Pack which is a 3-wire unit designed to work with ESU decoders, the ZIMO STACO3 is a simple 2-wire keep-alive which can be used with pretty much any decoder. Also worth mentioning that there are 2 versions of this module. STACO3A includes physically smaller caps (with less capacity), and STACO3B includes larger caps. I have not yet tested it in a model. Hoping to do it soon.
Here are photos showing the circuit board (front and back) and the pair of Super Caps, with a dime for size comparison. The board is 10 x 7.3 x 2mm and each cap is only 4 x 12mm The caps do not have to be physically near the board, and they can also be separate from each other, as long as they are wired correctly.
And this is the instructions insert (both sides). It is in German, but the hookup info is very clear.
The instructions state that it is vital to connect the polarized capacitors correctly, and that for charging it requires minimum of 11.3V (which would be around 12.5V DCC signal at the track, because the decoder's bridge rectifier drops around 1.2V). The maximum voltage for this unit is 18V.
The solder pads for the wires are present on both sides of the circuit board (the legends are on the bottom).
