What is the formula for LiPo charge time?

Time in hours equals the capacity to replace (in Ah) divided by the charge current (in A). Capacity to replace is the pack capacity multiplied by the percentage gap between current and target charge. The tool divides by an efficiency factor (typically 0.85) because chargers and packs are not 100% efficient, so real time is longer than the ideal.

What does charging at 1C mean?

A 1C charge rate means charging at a current numerically equal to the pack capacity. A 1500 mAh pack at 1C charges at 1.5 A and takes roughly one hour from empty. Many modern LiPo packs support 2C or higher, halving the time, but always follow the manufacturer's printed C-rating to avoid damage or fire risk.

Why is the estimate longer than capacity divided by current?

Real chargers taper the current during the final constant-voltage (CV) phase as the pack approaches full, so the last 10-20% charges more slowly than the bulk phase. The efficiency factor in this calculator approximates that taper plus conversion losses, giving a realistic time rather than the theoretical minimum.

Should I charge a LiPo to 100% if I am not flying immediately?

No. LiPo cells degrade fastest when stored fully charged. Charge to 100% only just before flying. For storage, charge or discharge to about 3.8 V per cell (roughly 50-60%). Set the target field to 60% to estimate a storage charge.

Is it safe to charge multiple packs in parallel?

Only with a proper parallel-charging board and packs of the same cell count and similar charge state. The charger current is shared across all packs, so total time depends on combined capacity. Charge unattended LiPos on a fireproof surface and never exceed the charger's rated output.

LiPo Charge Time Calculator

The LiPo Charge Time Calculator estimates how long a lithium-polymer battery will take to charge from its current state to your target level on a given charger. It is built for RC car, plane, drone and FPV hobbyists who need to know whether a pack will be ready before the next flight window — and who want a realistic figure rather than the idealised “capacity over current” number.

How it works

Charge time is fundamentally a matter of moving charge into the pack. The energy you need to replace is the pack capacity multiplied by the percentage gap between where the battery is now and where you want it:

capacity to replace (Ah) = pack_mAh / 1000 × (target% − current%) / 100
ideal time (h)           = capacity to replace / charge current (A)
real time (h)            = ideal time / efficiency

The efficiency factor (default 0.85) accounts for two real-world effects: conversion losses in the charger, and the constant-voltage taper at the top of the charge where current ramps down as the pack fills. Without it, the tool would always underestimate. Multiplying the result by 60 gives minutes.

For example, a 1500 mAh pack going from 20% to 100% needs 1.5 × 0.80 = 1.2 Ah. At a 1.5 A (1C) charge, the ideal time is 0.8 h; divided by 0.85 efficiency that is about 0.94 h, or roughly 56 minutes.

Tips and safety notes

The C-rate is the charge current divided by the capacity in Ah. Charging a 1500 mAh pack at 3 A is a 2C charge. Always stay at or below the pack’s printed maximum charge C-rating.
Charging faster (higher current) shortens time but generates more heat and shortens pack life. 1C is a safe, long-life default.
Storage-charge packs you will not use for several days to about 60% to slow chemical ageing. Set the target to 60% to estimate this.
Always charge LiPos on a non-flammable surface, ideally in a LiPo-safe bag, and never leave them unattended. This tool estimates time only — it is not a substitute for a quality charger with balance and over-voltage protection.