Zen SUPER high 2-wire power stay alive has exceptional power storage.
In fact, once charged, they have enough power to run an average OO or HO Locomotive more than two metres with the track power removed!
 
The overall size of Super Stay-Alives is a compact 32.3mm long x 16.1mm wide x 5.3mm high
Requires soldering of +ve and -ve wires to relevant solder pads on ESU LokSound decoders