This lithium-ion replacement battery for the Garmin Alpha 100 Handheld is small and compact, and very easy to install in your Alpha 100. It is so compact you may want to carry an extra, fully charged battery with you in the field to replace to trade out if you receive a low battery warning, as it only takes about 30 seconds to switch. These batteries will last 24-48 hours when fully charged depending on the update rate on your system. A fully depleted battery takes about 4 1/2 hours to charge.