What Is Battery C-Rate? Discharge Speed in Plain Language
Convert between amps, capacity, and how long a pack can sustain a load at 1C, 2C, or higher.
C-rate is how engineers talk about charge and discharge speed without guessing minutes. One C means a current equal to the capacity rating—100 A from a 100 Ah pack. Half C is gentler; two C is aggressive.
The basic relationship
Hours to empty (ideal) ≈ 1 ÷ C-rate. At 0.5C you have about two hours. At 2C, about thirty minutes. Real packs deviate because voltage sags and BMS limits kick in, but the rule frames expectations.
Why datasheets cap C
High C heats cells and shrinks effective capacity, especially on lead-acid. Lithium iron phosphate tolerates strong discharge better than some chemistries, but still has continuous and peak limits. Inverter surge current can demand 2C briefly even when average load is low.
Peukert on lead-acid
Lead-acid capacity collapses at high draw—a 100 Ah bank might behave like 70 Ah at heavy load. Lithium planning is closer to linear but not perfect.
Choosing gear with C in mind
Size inverter battery current for peak C within spec. Undersized packs sag voltage, trip low-voltage cutoffs, and look "bad" when they are simply overworked.
C-rate is a language, not a mystery. Learn to translate your load amps into C, compare to the datasheet, and you will stop blaming batteries for trips that were predictable on paper.