This Lithium-Ion battery is fully charged (using the Charger M3849A) in just 3 hours to provide 100 shocks (typical) or 5 hours (typical) of ECG display time. The "fuel gauge" on the FR2+ displays the battery's remaining power. Under normal conditions, the FR2+ Rechargeable Battery withstands 300 charge-discharge cycles or 2.5 years of use.