Samsung SDI INR18650-30Q

A 3 Ah 18650 cell rated for 15 A continuous, with the figures a pack design depends on and what each one was checked against.

Where these figures come from

Capacity, nominal voltage and continuous discharge confirmed against the manufacturer datasheet. Internal resistance is a published typical.

What it is for

The default answer for a general-purpose 18650 pack: near the top of the capacity range while still taking 15 A. Most builds that do not have an unusual requirement end here.

• Capacity: 3 Ah
• Nominal voltage: 3.6 V (2.5 V to 4.2 V)
• Continuous discharge: 15 A — 5.0C
• Internal resistance: 0.025 Ω
• Mass: 48 g

Questions

What is C-rate?

Current expressed as a multiple of capacity. A 3 Ah cell at 3 A is 1C; the same cell at 15 A is 5C. It is the number that decides whether a cell is being used gently or punished, and the rating that matters is the one on that cell’s own datasheet rather than a rule of thumb.

Do you recommend where to buy cells?

Not currently. Every cell page links to the manufacturer’s datasheet and nothing else. If supplier links are ever added they will be disclosed on the page, and the ranking will still be computed from electrical fit alone — a designer that recommends the cell paying the most commission is worthless, and it would look exactly like one that does not.