Cell datasheets are full of terms that decide whether a cell fits your pack. Here are the ones B2B buyers should understand.
Capacity (mAh / Ah)
How much charge a cell holds. A 5000 mAh (5 Ah) cell delivers 5 A for one hour in theory. Capacity sets runtime, but real usable capacity depends on discharge rate, temperature and depth of discharge.
C-rate
The charge or discharge current relative to capacity. For a 5 Ah cell, 1C = 5 A
and 2C = 10 A. A “5C continuous” cell can deliver 25 A continuously. High-drain
applications — power tools, drones — need high C-rate cells (the -P and -D
types); storage needs much less.
Energy (Wh)
Capacity × voltage. A 5 Ah cell at 3.6 V nominal holds about 18 Wh. Energy — not just mAh — determines runtime when you compare chemistries, because LiFePO4 (~3.2 V) and NCM (~3.6 V) differ in voltage.
Cycle life
How many full charge/discharge cycles a cell lasts before capacity falls to a threshold (often 80%). LiFePO4 leads here. Cycle life is rated at a specific C-rate, temperature and depth of discharge — always compare like for like.
Depth of discharge (DoD)
How deeply you use the cell each cycle. Shallower cycling extends life; LiFePO4 tolerates deep DoD better than other chemistries.
Internal resistance (IR, mΩ)
Opposition to current flow. Lower IR means less voltage sag under load, less heat and better high-rate performance. Consistent IR across a batch keeps multi-cell packs balanced.
Putting it together
A good cell choice balances all of these: enough capacity and energy for runtime, enough C-rate for the load, enough cycle life for the duty, and low, consistent IR for the pack. The right balance differs by application — compare formats in 18650 vs 21700 and chemistries in NCM vs LiFePO4.
Need exact figures for a model? Every spec above is on the datasheet. Request specs & a quote →