A free app for those who need to calculate how long it would take a charger to fully juice up your battery, especially if you use a trickle charger which does not send you an alarm notice if battery's already full. It's a free app now available at iTunes and this seems to be supported by ads so they don't need to "charge" you for using the app.

"Airsoft Charger is a very useful application for every airsofter. It calculates the time needed for your NiMH or NiCad battery to fully charge depending on their capacity (mAh). Airsoft Charger can also set a reminder to unplug your battery!"