thru my surfing on the computer, and having issues with the batteries going useless, it it my understanding that there is a "chip" in the batteries than when voltage drops below a certain parameter like on an 18 volt it is around 11 volts, charger renders battery pack useless...so i bot a non-ryobi variable voltage charger and charged battery past the parameter so it tricks ryobi charger that battery pack is now above the 11 volt parameter