Battery Doubler Doesn't Really Double Up

I installed the Battery Doubler, a program to increase my laptop's battery life. However, it didn't perform as I hoped it would. Battery life wasn't doubled as indicated by its name. Misleading. I uninstalled it soon after. I don't see any significant increase in my laptop's batttery life. It varies from computer to computer, but maybe it works best on low power settings so the battery life increase can be higher. So theoretically it's UP TO double of battery.