18650 Sodium-Ion Battery Cell (NFPP) 40C High-Rate Na-ion for DIY 12V, 24V, 48V Packs

Build high-current 12V, 24V, 36V, or 48V DIY battery packs with these 18650 NFPP sodium-ion cells, the rugged, cold-tolerant alternative to lithium-ion and LFP.

NFPP is the "LFP of sodium-ion": a phosphate cathode that trades energy density for safety, cycle life, and deep-cold performance. This high-rate cell pushes 40C continuous out of a standard 18650 can, so it fits the holders, spot welders, and nickel strip you already have. Sodium-ion runs a lower, wider voltage window than lithium, so the series counts and BMS settings are different. Everything you need to design around that is below.

Derated charge rates by temperature: -10°C to 0°C at 0.1C (3.30V max) · 0°C to 10°C at 0.2C · 10°C to 20°C at 0.5C · 20°C to 25°C at 1C · 25°C to 35°C up to 5C · 35°C to 60°C at 1C. No charging below -10°C. Cells ship at 2.0V or above.

Why NFPP Sodium-Ion

• Cold-weather performance. Delivers at least 85% of rated capacity at -20°C and at least 60% at -40°C. Even at a 10C load it holds at least 80% at -20°C. LFP loses a large share of its capacity in that cold, and can't be charged below freezing at all. This cell accepts a slow trickle charge down to -10°C.
• Serious current. 40C continuous from an 18650 is power-tool territory. A 4P group handles about 136A continuous on paper.
• Safer chemistry. No cobalt, no nickel. The phosphate cathode holds its oxygen tightly, which is why these cells pass overcharge to 6V, forced discharge to 0V, a 24-hour dead short, a 13 kN crush, impact, 1.5 m drops, and a 130°C hot box with no fire and no explosion.
• Stable supply chain. Sodium is refined from abundant soda ash and salt, and the cathode uses iron and phosphate. No lithium, cobalt, or nickel price swings.

The honest trade-off: NFPP carries less energy per pound than LFP, layered oxide sodium, or NMC. At ~71 Wh/kg this cell is built for current, cold, and cycle life, not range. If you need maximum watt-hours per dollar or per gram, look at our layered oxide sodium-ion 18650 instead.

How to Build a 12V, 24V, 36V, or 48V NFPP Pack

NFPP runs lower per cell than LFP (3.2V) and well below lithium-ion (3.7V), so the series counts differ from a lithium build. The formula never changes even if the cell does:

• Pack nominal voltage = series count (S) x cell nominal voltage
• Pack charge voltage = series count (S) x cell charge voltage

For the batch currently in stock (3.0V nominal, 3.70V charge):

Add cells in parallel (2P, 4P, 5P and so on) to scale capacity. A 16S5P 48V pack uses 80 cells, fits inside our 100-pack with 20 spares, and delivers 4.25Ah at roughly 204Wh.

A note on that low cut-off column. The cell is rated down to 1.50V, but the table uses about 1.8V per cell to leave headroom for cell-to-cell drift. Use 1.50V as the absolute floor, not your working setpoint. Also check your inverter or controller: NFPP's window is wider than LFP's, and most 48V inverters fault out around 40V, long before a 16S NFPP pack is empty. Size the series count to your inverter's input window, not just to the nameplate voltage.

BMS and Charger Setup

Do not use a lithium charging profile. Pull your setpoints from the Current Batch box above:

• Per-cell charge voltage: 3.70V
• Per-cell nominal: 3.0V
• Per-cell working low cut-off: about 1.8V (absolute floor 1.50V)
• Charge only at -10°C and above, and derate the current below 25°C

BMS. A stock lithium-ion or LFP BMS will not work out of the box; the voltage thresholds are wrong in both directions. You need a sodium-ion specific BMS or a programmable BMS that lets you set custom charge and discharge cut-offs. Daly, JK, and ANT units in their programmable variants are the ones sodium DIY builders reach for most. Confirm the model you buy allows a cut-off as low as 1.5V per cell, since some programmable lithium BMS units will not go below 2.0V.

Cold charging. Below 0°C the datasheet allows only 0.1C and a 3.30V charge limit. Most hobby BMS units can't change both current and voltage by temperature, so the simple, safe setup is to block charging below 0°C. Use the -10°C allowance only if your BMS or charge controller can enforce all three limits.

Charger. Use a constant-current / constant-voltage (CC-CV) supply set to the pack charge voltage from the table above, with termination around 0.05C. Do not connect an LFP or lithium-ion charger without reconfiguring the output. At 16S, an LFP charger set to 58.4V is close enough to look right but undercharges; a lithium-ion charger at 67.2V will push the pack far past its 3.70V per-cell ceiling.

Discharge and Storage Notes

The 0V forced-discharge result above is a safety test, not a usage spec. Repeated or long trips below 1.5V cost permanent capacity.

• Minimum discharge voltage: 1.5V per cell
• Recommended cut-off under load: about 1.7 to 1.8V
• Storage voltage: 2.0 to 3.2V per cell, dry, below 65% humidity
• Recharge any cells stored longer than six months

Spot Welding Recommendations

Sodium-ion cells do not take the same weld energy as lithium cells. Too much power damages the cell internally in ways you will not see until the pack underperforms.

1. Start at the lowest power setting your welder offers.
2. Keep each weld under 1.5 seconds.
3. If the tab does not hold, raise the power one step and repeat until the weld is secure. Stop at the first setting that works.
4. Pull-test a sacrificial cell before committing to a full pack.

New to sodium chemistry? Read our NFPP cell review and NFPP vs NFM before you design your pack.

A Note on Batch Variation

Sodium-ion is still a young, fast-moving chemistry, and cell manufacturers revise their products far more often than in the mature lithium world. The cells we stock change as better ones reach the market, which means capacity, current ratings, temperature limits, and cycle life can all differ from one batch to the next. The Current Batch box at the top of this page always reflects what is shipping today.

• Do not mix batches inside one series string. Cells of different capacity or internal resistance will not balance, and the smallest cell in the string sets the usable capacity of the whole pack.
• Buy all the cells for a pack in one order, including your spares. If you plan to expand later, order the extra cells now.
• Re-check your BMS and charger settings against the current datasheet whenever you order again.

Building something where the exact spec matters? Message us before you order and we will confirm what is physically on the shelf that day.

Datasheets and Previous Batches

Ordered from us before? Find your batch below. Both batches share the same 3.70V / 1.50V window, but current ratings and cold-charge rules differ, so use the row that matches the cells you actually have.

Not sure which batch you have? Send us your order number and we will tell you.