Measured at Batemo: the Samsung SDI INR21700-40T delivers 214 Wh/kg energy density and sustains 73 W continuous power in a 21700 cell.
Opened, measured and modelled at Batemo in Karlsruhe, Germany · 196 measured parameters per cell · not datasheet values
this cell342 more sample cells
ENERGY
The energy exchanged during the C/10 discharge described under Capacity, divided by the cell’s mass or volume. Measured directly, not calculated from the nominal capacity. Full definition
The energy exchanged during the C/10 discharge described under Capacity, divided by the cell’s mass or volume. Measured directly, not calculated from the nominal capacity. Full definition
The energy exchanged during the C/10 discharge described under Capacity, in watt-hours. Measured directly, not calculated from the nominal capacity. Full definition
POWER
The peak or continuous power above, divided by the cell’s mass or volume. Not a datasheet rating — the current behind it was measured on Batemo’s own test benches. Full definition
The peak or continuous power above, divided by the cell’s mass or volume. Not a datasheet rating — the current behind it was measured on Batemo’s own test benches. Full definition
The peak or continuous power above, divided by the cell’s mass or volume. Not a datasheet rating — the current behind it was measured on Batemo’s own test benches. Full definition
The peak or continuous power above, divided by the cell’s mass or volume. Not a datasheet rating — the current behind it was measured on Batemo’s own test benches. Full definition
Peak figures come from the highest current Batemo measured the cell to sustain briefly; continuous figures use the lower current it can sustain without interruption. Both stop at the same 2.5 V / 80 °C condition as the discharge measurements. Full definition
Peak figures come from the highest current Batemo measured the cell to sustain briefly; continuous figures use the lower current it can sustain without interruption. Both stop at the same 2.5 V / 80 °C condition as the discharge measurements. Full definition
CURRENT
The highest constant discharge current Batemo measured the cell to sustain briefly, before the same 2.5 V / 80 °C stop condition applies. Full definition
The highest constant discharge current Batemo measured the cell to sustain continuously, before the same 2.5 V / 80 °C stop condition applies. Full definition
PHYSICAL
Measured on the physical cell at Batemo, in Karlsruhe, Germany — not taken from the manufacturer's drawing. Volume is derived from the measured capacity and its volumetric density, not measured with a caliper. Full definition
Measured on the physical cell at Batemo, in Karlsruhe, Germany — not taken from the manufacturer's drawing. Volume is derived from the measured capacity and its volumetric density, not measured with a caliper. Full definition
Measured on the physical cell at Batemo, in Karlsruhe, Germany — not taken from the manufacturer's drawing. Volume is derived from the measured capacity and its volumetric density, not measured with a caliper. Full definition
Measured on the physical cell at Batemo, in Karlsruhe, Germany — not taken from the manufacturer's drawing. Volume is derived from the measured capacity and its volumetric density, not measured with a caliper. Full definition
CELL
Discharged from a full charge at a constant C/10 current and 25 °C, until the cell reaches 2.5 V or its surface reaches 80 °C. Nominal is the value from the datasheet; measured, gravimetric and volumetric are what Batemo recorded during that discharge. Full definition
Discharged from a full charge at a constant C/10 current and 25 °C, until the cell reaches 2.5 V or its surface reaches 80 °C. Nominal is the value from the datasheet; measured, gravimetric and volumetric are what Batemo recorded during that discharge. Full definition
The charge-averaged voltage across the same C/10 discharge — the exchanged energy divided by the exchanged charge, not a single number picked from a curve. It is a measured mean, not the nominal voltage printed on a datasheet. Full definition
In Batemo Insights
The table above gives you one capacity number. Below is what Samsung SDI INR21700-40T does under load — measured on our own test bench, across many operating points and several ambient temperatures. Every cell in the library is measured under identical conditions, which is what makes them comparable at all. At 1C — the one rate measured on every cell — usable energy is 87% to 99% of what the same cell delivers at C/10.
All three panels below use the same 12 measured operating points, at 25 °C ambient.
energy
12 pts · 25 °C · lin
The graph visualizes how much energy the cell can deliver when operated at different powers.
usable energy / Wh
discharge power / W
thermal
12 pts · 25 °C · lin
The greater the thermal losses, the more the cell heats up, resulting in higher depleted power.
max. surface temperature / °C
discharge power / W
runtime
12 pts · 25 °C · log
The more power the cell supplies, the shorter it can deliver the power.
runtime to cutoff / s (log)
discharge power / W
Every cell is a compromise. This cell's own measurements point to three challenges you will face with it. Each one shows the number behind it and where Batemo helps you solve it.
Cell selection
14.24Wh73W
and that is all a datasheet will tell you
Energy
second quarter of 343 cells
Continuous power
third quarter of 343 cells
the challenge
The datasheet says 4.00 Ah. But how much does it deliver in your system?
Looking at energy and power alone is not enough. Your duty cycle is neither C/10 nor 1 C, and somewhere in between the ranking between two cells can invert.
Cell selectionThermal analysis
about 68mW/cm²
of heat at typical operation — 3.7 W in total
heat out
heat out
54 cm² of surface
the challenge
I am asking this cell for 21.6 A all day, out of 66.7 g. Where does that heat go?
A surface temperature is not the temperature that decides. What no sensor on a finished cell can show is the temperature inside it — and the gap between the two grows exactly where it matters.
Thermal analysisLifetime
3.88Ah
measured at C/10 — the schematic curves above all start here
your end of life
cycles →
the challenge
This capacity describes the cell at the beginning of its life. How does it change under different operating conditions?
A cycle test tells you what happened under that one test. It does not tell you which mechanism took the capacity away, and it does not tell you what to change.
LifetimeThese three are the challenges this cell's own numbers raise. Which of them decides your product is something only your load profile can say — and that is the next question, not this one.
Batemo built a physics-based model of the Samsung SDI INR21700-40T from the measurements above, then checked it against the full set of validation experiments — discharge, charge, pulses and profiles. Across all of them the model deviates from the measurement by 0.031 V in voltage and 1.0 K in surface temperature, in root mean square. These are deviations Batemo measured, not a tolerance Batemo promises.
“If you can show us another battery cell model that is more accurate, we will refund your money.”
More on the Batemo Cell Model ›
Each value is the root mean square of the difference between measurement and simulation, across the full set of validation experiments for this cell — discharge, charge, pulses and profiles. A quarter of those experiments is known only to the party challenging the model, and not to Batemo. Model reference B0020.
Nearest by measured specific energy and power — the two axes of the Ragone map above. Not by chemistry, and not a recommendation. Other numbers, like continuous current, can still differ a lot.
The two closest cells in the library
Same build · 1.1% apart
Ring percentages measure overall distance — energy and power combined. The ×-numbers on the dashed box measure just one axis: a point on that edge has that many times this cell's own specific energy or power.
Closest behaviour · 0.5% apart
Ion, our battery decision assistant, joins this page after launch. Until then, these go straight to the engineers who measured this cell.
You can see four of its numbers here. We measured 196.
WHERE THE MEASURED NUMBERS STOP, THE DECISION STARTS.
Read by an engineer, not a mailbox. Reply usually within one working day.
Talk to our engineersWe have it. What it is worth depends on what you are building.
Some of its numbers are on this page. We measured 196 of them.
Internal resistance
One number on a datasheet. Every loss in your pack starts here.
Impedance spectrum (EIS)
An EIS curve is not a number. It is the input to a model.
Heat generation and thermal properties
Heat decides the enclosure. It is the number that is almost never on the datasheet.
Capacity loss after formation
A cell gives up capacity before it ever reaches your customer.
Spread across a measured batch
One measured cell is one cell. A pack is a batch.