Measured at Batemo: the CBAK 40135FS delivers 164 Wh/kg energy density and sustains 234 W continuous power in a other cylindrical cell.
Opened, measured and modelled at Batemo in Karlsruhe, Germany · 196 measured parameters per cell · not datasheet values
Available asData
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 CBAK 40135FS 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 14 measured operating points, at 25 °C ambient.
energy
14 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
14 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
14 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
66.57Wh234W
and that is all a datasheet will tell you
Energy
top quarter of 343 cells
Continuous power
top quarter of 343 cells
the challenge
The datasheet says 20.00 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 selectionSystem optimization
3.245V mean
this cell at C/10 — each dot a load case of an example cell
0
20
40
60
Ah/kg
C/10
1C
4C
8C
12C
datasheet
cut-off voltage
heat limit
measured load cases · example cell
the challenge
My pack has several hundred of these. The decision is not about the cell any more — it is about the system.
An equivalent circuit fitted to a handful of measurements reproduces those points and drifts everywhere else — which is exactly where a system study goes.
System optimizationBMS development
0–134.1A0–100% SOCup to 65°C
a BMS has to be right in every corner of this space
0
500
1000
W/kg
40 °C
25 °C
0 °C
−20 °C
hottest point
measured load points · example cell
the challenge
Between 76.8 A and 134.1 A my state-of-charge estimate has to hold. Where does it get the worst?
Every percent of estimation error is paid for twice: once as range nobody uses, once as margin nobody touches.
BMS developmentThese 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.
Every cell in the library is measured before a model is built from it. The mean accuracies are published as soon as the Batemo Cell Model is finished.
Every curve was recorded from a full state of charge, in a climate chamber under free convection. The model is built on these.
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
Also close · 26% 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.
Same build + closest behaviour · 7.5% apart
Ion, our battery decision assistant, joins this page after launch. Until then, these go straight to the engineers who measured this cell.
Some of its numbers are on this page. We measured 196 in total.
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.