Ryobi P150 Fuel Gauge

[Jim Frye]

At first glance, the Ryobi P150 Fuel Gauge might seem like a frivolous device, but after five months of use, I find it a very useful part of my cordless tool set. How many times have you grabbed a cordless tool, hiked upstairs or outside to use it, only to have the supposedly charged pack give up after a couple of minutes of use? I have had that experience many times. The $10 P150 takes the guess work out of picking a battery to use. I have six One+ packs and even though I take pains to ID which ones have had some usage since they were charged, I sometimes would grab one that wasn't up to snuff for the job at hand. Then it was back to the basement shop to fetch another pack, or two, to finish the job. With the P150, this is a non-issue. To use the fuel gauge, all you do is plug it onto the post of the battery pack in question. In a couple of seconds you know the status of the pack in four LED lights. The first thing the gauge does is run a test of the pack and counts down the test by lighting the red, yellow, and two green LEDs in that sequence. Then it turns the lights out and progressively lights the LEDs until it determines the amount of charge left in the pack. Here is the explanation from the P150 manual:
RED LED only: Battery pack needs recharging
YELLOW LED: Partial charge
One GREEN LED: High partial charge
Two GREEN LEDs: Fully charged
NO LEDs: Dead battery pack (completely discharged)
This simple little device has eliminated the trips back to the shop for more batteries. This will also let you check how well a pack is holding a charge on the shelf, so you know before you are stuck without a spare battery.
Oh yeah, it works with the LiOn packs also, even though they have a built in check button on them. The P150 just gives you a fourth level.