Lithium Ion Pouch Cell Discharge Rate: C Rating & Current Explained

A 3.7V 2000mAh pouch cell sold as “10C” will not deliver 20A in your product. On a bench at 25°C it might, for a few seconds, while the voltage falls and the surface climbs past 50°C. Ten minutes of that and your calculated runtime is off by a third.

What a pouch cell can actually push comes down to three things: rated capacity, the cross-section of the tabs carrying current out, and how fast heat leaves the stack.

What a C rating means in amps

A C rating is a multiple of capacity, not a current. Multiply by the capacity in amp-hours to get amps.

I (A) = C × capacity (Ah)

You want	Formula	On a 4500mAh cell
Amps from a C rating	I = C × Ah	2C = 9A
C rating from amps	C = I ÷ Ah	15A = 3.3C
Run time	minutes ≈ 60 ÷ C	2C = 30 min

On a 2000mAh cell, 1C is 2A and 3C is 6A. On the 3.7V 15Ah 148198, 1C is 15A. Same C number, seven and a half times the current.

Rated capacity is measured at 0.2C, and what you get at 2C is usually 5 to 10% lower before the cutoff steals more. The pouch cell capacity guide covers how much survives.

Why a pouch cell usually rates lower than a cylinder

The cathode is rarely the limit. LiCoO₂ and NCM move lithium fast enough for 20C pulses. What separates a pouch from an 18650 is the path current takes out, and the distance heat travels.

Tab width and foil thickness set the ceiling

Foils collect current and weld to tabs through the seal. On a small cell those tabs are often 3 to 5mm wide and 0.1mm thick, so 0.3 to 0.5mm² of copper. At a few amps per mm², that tab is good for 2 to 3A and warm well before 10A. A cylinder ends in a solid cap and a steel can that spreads heat. A pouch has one narrow window, and everything passes through it.

Heat has nowhere to go

A pouch is a flat stack inside 0.1mm laminate that insulates well in the through-plane direction. Heat born mid-stack travels sideways to the tabs or out through the face, and in a 100mm cell that is a long way. Hence the same electrodes can carry 3C in a 20mm cylinder and 1C in a 10mm pouch. The aluminum plastic film seals well and conducts heat badly.

Reading a discharge spec without getting fooled

Continuous and peak are different products

Continuous means current until cutoff with the cell under its temperature limit. Peak means something shorter, and the length of “shorter” is the whole specification.

The sheet says	Ask	A straight answer
“20C discharge”	How long, at what temperature?	20C for 10s at 25°C
“3C continuous”	Surface temperature at the end?	45°C, 25°C ambient
“800 cycles”	What depth, what rate?	80% DoD, 1C
“No loss at high rate”	Against what baseline?	92% of the 0.2C figure

A C rating with no time window is a marketing figure. Ask for the window, ambient temperature, cutoff and end-of-test surface temperature.

Small print that moves the number

Internal resistance roughly doubles between 25°C and 0°C, and at −10°C a cell rated 2C may take only 0.5C without plating lithium on the next charge. A figure measured to 2.5V also includes capacity a device cutting off at 3.3V never sees; the voltage and discharge curve guide shows how much.

What high current costs you

IR drop. A 2000mAh LiCoO₂ pouch sits around 50 to 80mΩ. At 2A that costs 0.12V, at 6A it costs 0.4V. With cutoff near 3.3V, a slice of stored energy never gets used: you paid for 2000mAh and shipped 1600.

I²R heating. Double the current and heat in the tabs and foils quadruples. Heat raises resistance, and resistance raises heat.

Electrode stress. The stack flexes and the SEI pays.

Discharge rate	Capacity retention after 300 cycles
0.5C	90 to 93%
1C	85 to 88%
2C	78 to 82%
3C and above	65 to 75%

Read those as typical; the spread is mostly heat management. Swelling is the visible symptom: a pouch that has grown 3 to 4% after a few hundred hard cycles has been run past its window, and once the laminate pillows it is finished.

[IMAGE 2 HERE] Discharge curves at 0.5C, 1C and 2C, with the 3.3V device cutoff marked.

Worked example: sizing from a load profile

A handheld medical monitor on a 3.7V rail draws 0.4A average, pulls 1.8A for 20 seconds per measurement cycle, and needs 8 hours at up to 40°C.

Step	Work	Result
Energy	0.4A × 8h	3.2Ah
Peaks	1.8A × 20s, 12 cycles/h	under 0.1Ah
Derate for 40°C	+20% for cycle life	3.8Ah target
Peak C rate	1.8 ÷ 3.8	0.47C
Model	8025100, 4000mAh build	comfortable margin

A half-C peak is nothing. Most handheld products sit here, where thickness picks the cell and rate never binds. A drone at 12A on a 4500mAh pack runs 2.7C, and a 30A punch is 6.7C; there, tabs and airflow drive the design.

Series and parallel: what changes per cell

Parallel cells split current. Series cells do not. A 3S pack at 2C pushes 2C through every cell in the string; a 3S2P pack at 2C pushes 1C through each.

Build	Pack voltage	Pack capacity	Pack 2C	Per cell
1S1P	3.7V	2.0Ah	4.0A	4.0A
3S1P	11.1V	0.85Ah	1.7A	1.7A
1S2P	3.7V	3.0Ah	6.0A	3.0A
3S2P	11.1V	1.7Ah	3.4A	1.7A

If a cell cannot take the current alone, put a second one beside it, not behind it. The 3S 850mAh pack and the 1S2P 3000mAh pack are two arrangements of that idea.

The parts that fail before the cell does

Protection board. A 15Ah cell behind a 5A PCM is a 5A battery. PCM ratings are often the real ceiling.

Wire. 22AWG carries 1.5 to 2A on short internal runs, 20AWG 2.5 to 3A, 18AWG 4 to 5A. Thin wire adds series resistance, so sag at the connector is worse than at the tab.

Connector. JST PH 2.0 is rated 2A, an XT30 30A, an XT60 60A.

Pouch cell models and their discharge headroom

Model	Capacity	Energy	Size (mm)	1C	Typical continuous	Fits
8025100	2000mAh	7.4Wh	8 × 25 × 100	2A	2A, peaks to 4A	GPS, handhelds, medical
134365	4500mAh	16.65Wh	13 × 43 × 65	4.5A	4.5A, high-rate on request	drones, RC, power tools
148198	15Ah	55.5Wh	14 × 81 × 98	15A	15 to 30A with wide tabs	power banks, solar, light EV

The 148198 puts 55.5Wh into 111cm³, near 500Wh/L. That density costs rate headroom, which the Wh/kg vs Wh/L comparison sets out.

Continuous figures depend on tab width, PCM rating and mounting. The 134365 platform can be built far higher, with 20C quoted for specific builds; ask for the pulse window and surface temperature first.

Every model in the pouch cell battery range takes the tab, wire, connector and PCM the load needs. Send a load profile rather than a part number.

FAQ

Does a higher C rating always mean a better cell?

No. Rate capability is bought with thinner electrodes, wider tabs and more electrolyte, all trading against energy density. A 20C cell holds less energy than a 1C cell of the same size, and costs more. Pick the lowest rating that covers your peak.

Can I exceed the continuous rating occasionally?

Usually, if the excursion is short and the start temperature low. 3C for five seconds at 25°C is reasonable. 3C for two minutes in a sealed 45°C housing is a warranty claim in progress.

What limits pouch cell discharge rate more, chemistry or tabs?

Below about 10Ah, usually the tabs and the heat path. Chemistry sets the ceiling; tab area and laminate thermal resistance decide how much of it you reach.

Does discharge rate affect cycle life?

Yes, more than most datasheets admit. 1C costs a few points of retention over 300 cycles against 0.5C, and 3C costs a lot more. Heat is the mechanism, so a well-cooled 2C pack can outlast a badly housed 1C one.

Choose the rate before you choose the cell

Start with the load profile: continuous amps, peak amps, peak duration, and the ambient temperature inside the enclosure. Convert to a C rate against the capacity you chose for runtime. Then check tab, PCM, wire and connector, in that order.

Do that and the C rating stops being a claim to argue about.