Ask a datasheet for an NMC pouch cell's voltage and you will get several numbers, each describing a different moment in the cell's life. Mixing them up is easy, and the consequences show up at the system level: a charger that overshoots, a controller running closer to its limit than anyone intended, a BMS configured for the wrong window.

LiTrue's own guide to NMC pouch cell voltage starts from that confusion. This note pulls out the practical part: three numbers to know, and one table that does most of the arithmetic for you.

Three Voltages, Three Jobs

• Nominal voltage (3.7V per cell for standard NMC): the average working voltage, used to label a cell and size a pack's nominal system voltage.
• Full-charge voltage (about 4.2V per cell): the upper cutoff, the point at which the charging circuit should stop pushing current into the cell.
• Discharge cutoff (2.75V per cell): the lower limit where discharge should stop. LiTrue's guide lists a resting voltage of roughly 2.75V to 3.00V per cell at 0% state of charge.

The nominal number is the one on the label, but the other two are the ones the rest of the electrical system has to survive.

What Series Count Does to Those Numbers

Series connection adds voltage; parallel strings add capacity and current capability without changing voltage. Multiplying each per-cell figure by the series count gives the pack-level window:

Computed from the per-cell values above. The 14S figures (about 51.8V nominal, 58.8V fully charged) match those in LiTrue's voltage guide.

The 14S row is the one that surprises people. A pack sold as "51.8V" sits about 7V higher at the top of its charge, and about 13V lower at the bottom of its discharge window. That is the range every downstream component actually sees.

Why the Top of the Range Is the Number to Design For

A chain of components shares a pack's voltage: the charger, the motor controller or ESC, the BMS, connectors, and any DC-DC converters. Each has a voltage ceiling, and the relevant comparison is against the fully charged figure, not the label. A part with a 60V ceiling, for example, leaves only about 1.2V of margin above a fresh 14S charge of 58.8V. That is workable only if the charger and BMS are configured precisely, and it leaves little room for a charger tolerance or a regenerative spike.

The same reading applies at the bottom. Under load, a cell's voltage sags, and the curve falls away as the cell approaches empty. A BMS cutoff, a low-voltage alarm on a flight controller, and the point at which a motor controller gives up should all be set against the discharge cutoff and the sag behavior at the load the cell will actually carry.

Two "51V" Packs That Finish at Almost the Same Voltage

Chemistry changes the per-cell numbers, so the same system voltage can mean different things. LiTrue's custom-cell guide gives a useful comparison: a 14S NMC pack on 3.7V cells is about 51.8V nominal and 58.8V full, while a 16S LFP pack on 3.2V cells is about 51.2V nominal and 58.4V full. The nominal figures look nearly identical, and so do the full-charge figures, but the cell counts, capacities, and discharge curves are different. Swapping one chemistry for the other in the same housing therefore needs more than a matching label: the charger profile, BMS limits, and state-of-charge logic all have to follow the chemistry.

Four Numbers to Confirm on Any Datasheet

LiTrue's guide boils the checklist down to four items worth requesting explicitly from any cell supplier:

• Nominal voltage
• Charge cutoff (upper limit)
• Discharge cutoff (lower limit)
• The rated C-rate at which those cutoffs were tested

The last item is the one most often missing. A cutoff measured at a gentle rate says little about where a cell will sit under a hard pull.

A cell such as the 50Ah high-rate NMC pouch cell (PA50N-P) uses the standard 3.7V-class arithmetic above, and LiTrue's 51.8V UAV packs, such as the UAV-JP328L, are built in a 14S configuration. For a target platform that does not match a standard voltage, LiTrue can configure series-parallel arrangements and supports custom cells and packs. The full range is in the product catalog.

The Bottom Line

Voltage on a pack label is a nominal average. The numbers that decide whether a charger, controller, and BMS work together are the full-charge ceiling and the discharge floor, measured at the load the system will really see. Writing those two figures into the design brief early is cheaper than discovering them at first power-up.

If you are specifying a pack for a particular voltage platform, LiTrue's engineering team can help you map cell count, cutoffs, and C-rate to your charger and controller limits — request a quote here.