Detailed Answer
Replacement intervals: lithium battery: 2-3 years (500 cycles) or when runtime drops noticeably; NiMH: 1-2 years (capacity decay); alkaline: replace when used up (high leakage risk, remove when not in use). Criterion: replace when runtime is <50% of a new battery. Lider LD series lithium versions run 5-10 days (8 h/day); replace the battery when runtime drops sharply.
| Lithium | 2-3 years |
| NiMH | 1-2 years |
| Criterion | Runtime <50% |
Note:Alkaline battery leakage can damage the circuit — prefer rechargeable batteries.