You're going out on a trip and planning to bring charged batteries. When comparing against candles for emergency purposes, you have to adjust for the fact that

You're going out on a trip and planning to bring charged batteries. When comparing against candles for emergency purposes, you have to adjust for the fact that emergencies are unplanned. Batteries lose charge over time (especially the rechargeable ones we use), which makes them much less useful for emergencies. Compare with candles, which do not lose 'charge' over time.