FWIW the POB charger supplies 20.52 volts DC in its open circuit, but energized state. (plugged in wall but not to light) Being an unregulated power supply once hooked up to the substantial load of the POB's SLA battery this should drop to 13.5v or so then rise to appx. 14.4 as the battery reaches full charge.
I've seen wall warts rated at 12v that when checked in open circuit were barely above 14v, surely some may be as low as 13.8. (though on average most are around 15)
Be sure nobody sells you a power supply/charger based on its open circuit output. For funzies I tried a 12v 1000ma charger (as supplied by centralLED for its work light) which showed 15.5 open circuit volts on my POB. It didn't register its presence on the "now charging" light. (while the POB's charger did, even with a charged battery for a moment)
(I have several "universal" chargers and a digital bench power supply made by BK Precision. I had a spendy minolta digital camera but lost its charger a couple of years ago- I figured the universal would suffice, double checked the voltage setting at 4.5, triple checked the polarity, and plugged it in... and saw smoke coming out. Fried a $500 camera. It wasn't till a week later I found the cause was not my own stupidity but the cheap construction of the universal power supply. The voltage selection switch had broken internally, despite me selecting 4.5 and feeling a distinct detent stop at that setting, the switch was broken at 12v. Giving the camera 16v, actually, by my DMM check. Who knew?)
I still find those universals are great for powering a squirrel cage blower to blow under your laptop. Adjusts the speed nicely, and unlike laptop coolers doesn't hook up to the USB and overheat the laptop's power supply.
