Purchased a Ryobi P150 "Fuel Gauge" to check status of my P100 One+ batteries.
Instructions state that each of the four LEDs will sequence "on" to evaluate status, then "go out". Then, one or several of the colors (red, yellow, green(2)) will reappear to indicate the charge status.
When I placed the Gauge on each of my batteries, after the initial evaluation sequence, all four LEDs illuminated collectively, and remained lit.
I emailed Ryobi Support (One World Technologies, Inc), and they said the unit "could" be defective. I returned it to Home Depot and got a replacement. Guess what ... same problem.
The Ryobi P150 is not a charger, it is a Gauge that fits on the stem of a Ryobi One+ battery to read the existing charge. It is suposed to tell you whether the battery is fully charged, partially charged, or needs charging.
I don't have one, but would like to hear from anyone who has one as to whether it is worth getting. I have a voltmeter that I use to check my batteries, it sits next to both my charged and discharged batteries, it is very handy, not sure the battery tested would be any easier.
The report in this thread is not very encouraging.