Cell Review: Sodium-ion NFPP, 18650
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NFPP Sodium-Ion Cells: The Sodium Answer to LFP
Why this matters: Sodium-ion is growing fast and there are many new variants available. This post covers NFPP specifically, the sodium-ion cousin to LFP (LiFePO4), in two formats:
- 18650 NFPP high-rate cylindrical cell (850 mAh, 40C): for bench testing, prototyping, education, and high-current packs.
- 160Ah NFPP prismatic cell: a large-format cell for serious storage builds (solar, backup, BESS).
Both cells run on sodium, not lithium. No lithium, no cobalt, no nickel pricing drama. This is the early shape of lithium-free stationary storage.
Chemistries at a Glance
NFPP stands for sodium iron phosphate pyrophosphate (Na4Fe3(PO4)2P2O7). It's a polyanion cathode, the same structural idea as LFP: the phosphate groups lock the oxygen in place, which is why these cells shrug off abuse that would send a lithium oxide cell into thermal runaway. It's paired with a hard carbon anode.
Neither datasheet names the cathode, so here's how we know what these are. Both cells run 3.0 V nominal with a 3.7 to 3.8 V charge ceiling. That's the NFPP window. The vanadium fluorophosphate cathode (NVPF) you'll see quoted on some listings runs closer to 3.6 V nominal and charges past 4 V. Our previous 900 mAh NFPP 18650 gained only about 2% capacity when charged to 4.0 V instead of 3.7 V, which is also what you expect from a phosphate cathode: almost nothing left to give above its window.
They are not NFM layered oxide (NaNi1/3Fe1/3Mn1/3O2). NFM chases higher energy density and a higher charge voltage, while NFPP leans into safety, long cycle life, and cold-weather discharge. If you want the best Wh/kg, that's layered oxide. If you want "will it still give current at −20 °C," that's NFPP. More in NFPP vs NFM, or see our layered oxide 18650 review for the other side.
Product #1: NFPP Sodium-Ion 18650 High-Rate Cell (850 mAh, 40C)
Batch note: This section covers the new 850 mAh high-rate cell (model 18650H-D, made by Henan Meddore). It replaces our earlier 900 mAh, 20C NFPP cell. The two cells share the same 1.5 to 3.7 V window, but the current limits and cold-charge rules are different. If you bought the 900 mAh cells, your settings are in the previous batch table below.
This is a high-rate rechargeable sodium-ion 18650. The spec sheet calls it a "Wide Temperature & High Rate" cell, and it means it: 40C continuous out of an 18650 is power-tool territory. It trades a little capacity for that current, which is the right trade for pulse loads and the wrong one if you only care about Wh per dollar.
Key Electrical Specs
| Parameter | Spec | Notes |
|---|---|---|
| Model | 18650H-D (18650-850mAh) | Henan Meddore New Material Co. |
| Chemistry | Sodium-ion, NFPP polyanion cathode | No lithium, cobalt, or nickel |
| Nominal Voltage | 3.0 V | |
| Voltage Window | 1.5 V to 3.7 V | Charge limit and max float are both 3.7 V |
| Rated Capacity | 850 mAh @ 0.2C (1.5 to 3.7 V) | Minimum 800 mAh |
| Energy | ~2.55 Wh per cell | ~71 Wh/kg |
| Internal Resistance | ≤16 mΩ | AC 1 kHz after standard charge |
| Standard Charge Current | 0.5C | CC/CV to 3.7 V, stop at ≤0.05C |
| Max Charge Current | Up to 5C at 25 to 35 °C | 1C at 20 to 25 °C; see temperature table |
| Standard Discharge Current | 0.5C | To 1.5 V cutoff |
| Max Continuous Discharge | 40C (34 A) | Rated at 25 °C; 35C (≈30 A) is the 20 to 45 °C operating limit |
| Peak Discharge | 60C (51 A) for ≤5 s | Short bursts |
| Cycle Life | ≥1,200 cycles to ≥85% capacity | 1C charge / 1C discharge, 3.7 to 1.5 V |
| Operating Temp (Charge) | −10 °C to +60 °C | Below 0 °C: ≤0.1C and 3.3 V max |
| Operating Temp (Discharge) | −40 °C to +70 °C | Current derates at the extremes |
| Dimensions | 18.41 mm × 65.50 mm | Standard 18650 can |
| Mass | 36.0 ±0.5 g | Lighter than a typical 45 to 48 g Li-ion 18650, but it stores far less energy, so Wh/kg is lower |
Source: Henan Meddore, Wide Temperature & High Rate Sodium Ion Cell Specification, 18650H-D, Rev A1. Download the datasheet (PDF).
Cycle Life at High Rate
Most datasheets give you one cycle number at a gentle rate. This one shows what fast charging and discharging costs you, all at 25 °C, 3.7 to 1.5 V:
| Charge / Discharge Rate | Cycles | Capacity Remaining |
|---|---|---|
| 1C / 1C | 1,200 | ≥85% |
| 3C / 3C | 1,000 | ≥70% |
| 5C / 5C | 800 | ≥70% |
| 7C / 7C | 500 | ≥70% |
The pattern is the physics: higher current means more heat and more stress on the electrode structure every cycle. If your load only pulls 40C for a few seconds and the rest of the time sits near 1C, you'll live near the top row.
Temperature / Rate Behavior
- −20 °C discharge: ≥85% of rated capacity at 0.5C.
- −40 °C discharge: ≥60% of rated capacity at 0.5C. You can still pull energy at −40 °C.
- Cold and fast at once: at a 10C discharge, ≥85% capacity at −10 °C and ≥80% at −20 °C.
- 55 °C discharge: ≥95% of rated capacity at 0.5C.
- Discharge current limits by temperature: 35C from 20 to 45 °C, 30C from 0 to 20 °C, 20C from −20 to 0 °C, 10C from −30 to −20 °C, 5C from −40 to −30 °C, 5C from 45 to 60 °C, and 1C from 60 to 70 °C.
- Charge current limits by temperature: ≤0.1C from −10 to 0 °C (with a 3.3 V limit), ≤0.2C from 0 to 10 °C, ≤0.5C from 10 to 20 °C, ≤1C from 20 to 25 °C, ≤5C from 25 to 35 °C, ≤1C from 35 to 60 °C. No charging below −10 °C.
That temperature window is the story, and this cell moves it. It discharges in deep cold far better than LFP, and unlike LFP it can take a slow trickle of charge down to −10 °C. Read the fine print on that: below 0 °C the limit is 0.1C and the charge voltage drops to 3.3 V, so you're topping up, not filling. A solar bank in a shed at −5 °C will keep accepting a little charge. Below −10 °C it won't accept any. Your system has to manage all three numbers (temperature, current, and voltage) at once, which most hobby BMS units can't do. The simple, safe setup is a BMS that blocks charging below 0 °C. Cold trickle charging needs a BMS or charge controller that can drop both current and voltage by temperature.
Abuse / Safety
- Overcharge to 6.0 V at 1C for up to 1 hr: no fire, no explosion.
- Forced discharge to 0 V, then held under load for 90 min: no fire, no explosion, no leakage.
- External short at ≤5 mΩ for up to 24 hr: no fire, no explosion.
- Crush to 13 kN, 9.1 kg impact bar, 1.5 m drops, 130 °C heat soak, and 32 cycles of −40 to 85 °C thermal shock: no fire, no explosion.
This is classic phosphate behavior: it resists runaway under abuse. One caution: the 0 V test is a safety test, not permission to run the cell flat. The datasheet warns that long over-discharge costs performance, so store it between 2.0 and 3.2 V per cell and recharge anything that sits longer than six months.
Previous Batch: 900 mAh, 20C
Bought NFPP 18650s from us before this batch? Use the column that matches the cells you actually have. Don't mix the two in one series string.
| Parameter | 850 mAh (current) | 900 mAh (previous) |
|---|---|---|
| Charge / Discharge Limits | 3.7 V / 1.5 V | 3.7 V / 1.5 V |
| Max Continuous Discharge | 40C (34 A) | 20C (18 A) |
| Max Charge Current | 5C (25 to 35 °C) | 3C (25 to 35 °C) |
| Coldest Charge | −10 °C at ≤0.1C, 3.3 V max | 0 °C (no charge below) |
| Cycle Life (1C/1C) | ≥1,200 to 85% | ≥1,000 to 85% |
| Internal Resistance | ≤16 mΩ | ≤20 mΩ |
| Weight | 36.0 g | 33 g |
| Datasheet |
Typical Uses
- Bench testing sodium-ion pack design (12 V / 24 V / 48 V nominal strings).
- High-current loads: a 4P group of these handles about 136 A continuous on paper. E-bike and scooter packs, power tools, and inverter surge loads.
- Low-voltage backup, UPS, and portable storage prototypes, especially anything that lives outdoors.
- Education, demos, YouTube content, and R&D proof-of-concept.
➜ Shop NFPP Sodium-Ion 18650 Cells
➜ Shop NFPP Sodium-Ion 18650 Cells
Product #2: 160Ah NFPP Sodium-Ion Prismatic Cell (For Stationary Storage)
This is a large-format sodium-ion prismatic cell: model SIB-P71173208-160Ah. This is not a flashlight cell. It's a rack-level building block for solar storage, backup power, and BESS.
It also shares the footprint of the 280Ah to 314Ah LFP cells most DIY builders already know: same 71.7 mm thickness and 173.7 mm width, 2.6 mm taller. Fixtures, busbar spacing, and compression plates built for that family carry over.
Key Electrical Specs
| Parameter | Spec | Notes |
|---|---|---|
| Model | SIB-P71173208-160Ah | Prismatic sodium-ion cell |
| Nominal Voltage | 3.0 V | Same 3 V class as the 18650 |
| Nominal Capacity | 160 Ah @ 0.2C | ≈480 Wh per cell, ~114 Wh/kg |
| Charge Voltage (max) | 3.8 V | CC/CV to 3.8 V, stop at ≤0.05C |
| Discharge Cutoff | 1.5 V | Below this the manufacturer voids the warranty |
| Standard Charge / Discharge Current | 0.5C (≈80 A) | For rated performance |
| Max Charge Current | 1C (≈160 A) | |
| Max Continuous Discharge | 2C (≈320 A) | High current for a stationary-format cell |
| Pulse Discharge | 3C for 30 s @ 100% SOC | ≈480 A bursts at 25 °C ±2 °C |
| Internal Resistance | ≤0.65 mΩ | AC 1 kHz after standard charge |
| Operating Temp (Charge) | 0 °C to +55 °C | Charging below 0 °C is prohibited |
| Operating Temp (Discharge) | −40 °C to +60 °C | ≥80% capacity at −20 °C (1C) |
| Mass | 4.2 ±0.2 kg | Per cell |
| Dimensions | 71.7 mm (thick) × 173.7 mm (wide) × 207.2 mm (tall) | Thickness measured under 200 kgf preload; performance tests run at 300 kgf |
Source: PORFFOR Product Specification, SIB-P71173208-160Ah. Download the datasheet (PDF).
Cycle Life / Degradation
-
Standard cycle test: 0.5C charge to 3.8 V, 0.5C discharge to 1.5 V at 25 °C. The spec calls out:
- ≥6,000 cycles to 80% of initial capacity
- ≥10,000 cycles to 70% of initial capacity
- Charge retention after 30 days at 25 °C: ≥90% of original capacity, with ≥95% recovery after recharge.
- Low-temp discharge at −20 °C (1C to 1.5 V after cold soak): ≥80% of room-temp capacity.
That's LFP-grade cycle life on paper, and it keeps discharging well below freezing without a heater blanket. One honest caveat: these are manufacturer qualification numbers at 25 °C and 0.5C. Sodium-ion doesn't have a decade of field history yet the way LFP does.
Abuse / Safety
- Overcharge to 6 V at 1C for 90 min: no fire, no explosion.
- External short at ≤5 mΩ: no fire, no explosion.
- Crush until 0 V, 30% deformation, or 200 kN: no fire, no explosion.
- Heat to 130 °C for 30 min: no fire, no explosion, no leakage.
- Seawater immersion (3.5% NaCl) for 2 hours: no fire, no explosion.
This is what you want sitting in a steel box bolted to the side of a building.
Intended Use
- Stationary storage (off-grid solar, backup power, microgrids, commercial ESS).
- Outdoor or unheated enclosures where the bank needs to deliver power in deep cold. Plan for charging only above 0 °C, either with mild heat or a BMS that holds off charge until the cells warm up.
- Sites where you want to avoid lithium (insurance, AHJ comfort level, policy).
- High-cycle daily-use storage (PV plus load shifting). The 6,000 to 10,000 cycle figures come from the manufacturer's qualification spec, not marketing copy.
➜ Shop 160Ah Sodium-Ion Prismatic Cells
NFPP vs NFM vs LFP: When to Use What
| Chemistry | Nominal V | Energy Density | Cycle Life | Cold Performance | Main Use Case |
|---|---|---|---|---|---|
| NFPP sodium polyanion (these cells) | ≈3.0 V | ~80 to 115 Wh/kg, similar to early LFP | 6,000 to 10,000 cycles spec'd in prismatic format | Excellent discharge (−20 °C and even −40 °C). Charging: 0 °C minimum on the prismatic; trickle to −10 °C on the new 18650. | Solar storage, backup, outdoor enclosures |
| NFM layered oxide (NaNi1/3Fe1/3Mn1/3O2) | ≈3.1 V | Higher Wh/kg | Good (typically a few thousand cycles) | Good, but usually not spec'd for −40 °C discharge at useful load | Where size and weight matter more than extreme abuse tolerance |
| LFP (LiFePO4) | ≈3.2 V | High Wh/L in mature prismatic formats | 6,000+ cycles is normal | Fair: weak discharge in deep cold, no charging below 0 °C | Home batteries, commercial storage, EV packs today |
In plain English:
NFPP sodium-ion = rugged, cold-discharge, safe.
NFM sodium-ion = higher energy density sodium.
LFP lithium = mature, better energy density, weaker in the cold.
Integration / BMS Notes
- Charge limit: 3.7 V per cell for the 18650, 3.8 V per cell for the 160Ah prismatic. Do not treat them like 4.2 V Li-ion cells or use an LFP charger profile without reconfiguring it.
- Low cutoff: 1.5 V per cell is the absolute floor for both, not your working setpoint. Set the BMS a little higher (around 1.7 to 1.8 V per cell under load) to leave headroom for cell drift. Most inverters will fault out well before the floor anyway, so check your inverter's low-voltage window when picking a series count.
- BMS: A stock lithium BMS won't work out of the box. Use a sodium-specific BMS or a programmable one, and confirm it lets you set a cutoff as low as 1.5 V per cell. Some programmable lithium units won't go below 2.0 V.
- Cold charging: Never charge the 160Ah prismatic below 0 °C. The new 18650 allows a 0.1C trickle at 3.3 V max from −10 to 0 °C, but unless your BMS can enforce that, block charging below 0 °C for both. Above freezing, limit current at the low end (≤0.2C from 0 to 10 °C on the 18650).
- Balancing: In multi-cell packs, you must balance. The prismatic datasheet requires a BMS with active equalization across cells.
- Storage: The prismatic ships at 2.5 to 3.0 V and should be stored between 1.5 and 3.0 V. For storage longer than 3 months, check voltages every 3 months and top up any cell below 1.5 V. Store the 18650 between 2.0 and 3.2 V and recharge it if it sits longer than six months.
- Compression: The 160Ah prismatic is spec'd and tested under 200 to 300 kgf of preload. Treat it like modern LFP prismatics: it's designed to live clamped in a module, not loose in a tote bin.
- Don't mix cells: Do not mix part numbers, revisions, or batches inside one series string. That includes our 900 mAh and 850 mAh NFPP 18650s.
Bottom Line
Sodium-ion is past the "hype deck" stage and into real hardware:
- The 18650 NFPP cell is ready for builders, educators, and anyone who wants to measure real sodium behavior instead of reposting LinkedIn slides. The new batch pushes it to 40C continuous and slow charging down to −10 °C.
- The 160Ah prismatic cell is aimed at actual storage systems, with multi-thousand-cycle life and real subzero discharge. It's an LFP alternative you can mount in an unheated shed, as long as you plan for charging above freezing.
If layered oxide is the high-energy sodium chemistry, NFPP cells are the workhorses: the sodium answer to LFP.
➜ Shop NFPP Sodium-Ion 18650 Cells
➜ 160Ah Sodium-Ion Prismatic Cells for Storage Builds
Specs are taken from the manufacturer datasheets for the 18650H-D (850 mAh), 18650-900mAh, and SIB-P71173208-160Ah cells and may change between batches. Always confirm pack voltage limits and BMS settings against the datasheet for the cells you actually have before final integration.