3–3.5-inch FPV freestyle and toothpick motor
MEPS SZ1604
A 12 g T-mount 1604 for 3–3.5 inch quads in 2850KV (6S) and 3800KV (4S); on MEPS's bench it pulls 611.4 g at 25.2 V (2850KV) and 520.2 g at 16.8 V (3800KV), both on an HQ3520-3.
- 3–3.5 inch freestyle, toothpick and whoop builds
- 6S (2850KV) or 4S (3800KV)
- 3.5-inch props such as the HQ3520 on a T-mount
The spin is an illustration: the model turns at 1/600 of the no-load speed, and it is a generic 1604 motor drawn from MEPS’s published sizes, not its exact design. Thrust, current and power are MEPS’s bench figures for the HQ3520-3 prop at 25.2 V, read straight across between its throttle steps. Its data starts at 10% throttle.
- Max thrust
- 611 g
- HQ3520-3 prop, 25.2 V
- Weight
- 12 g
- with cable, both KVs
- Peak current
- 14.8 A
- full throttle
Plain links: we earn nothing from them.
What it pulls
MEPS’s own bench test, one line per prop. Drag across the chart to move the throttle; the model above follows.
At 60% with the HQ3520-3: 346 g of thrust, 6.1 A, 0 W, 2.27 g per watt.
On your quad
3.8 : 1
Thrust to weight at full throttle: four motors pull 2,446 g with the HQ3520-3 at 25.2 V.
At 60% throttle they pull 1,384 g, 2.1 times the quad’s weight.
All-up weight is the quad ready to fly, with its battery and camera. The thrust is the maker’s static bench figure; in the air it is lower.
What you get
611.4 g on 6S
On MEPS's 25.2 V bench the 2850KV pulls 611.4 g at full throttle on an HQ3520-3, drawing 14.8 A.
Source: MEPS 2850KV data test
520.2 g on 4S
The 3800KV pulls 520.2 g on the same prop at 16.8 V, drawing 18.7 A.
Source: MEPS 3800KV data test
12 g
Both KVs weigh 12 g including 120 mm of 24 AWG lead.
Source: MEPS spec table
T-mount
A 1.5 mm steel shaft with four M2 prop holes on a 5 mm circle, which MEPS says keeps props from loosening and the shaft from bending in crashes.
Source: MEPS product page, MEPS size chart
What to pair it with
Our reading of MEPS’s numbers, so your build matches what the motor was tested with.
- ESC
- MEPS's peak currents are 14.8 A (2850KV, 6S) and 18.7 A (3800KV, 4S); the 3800KV drew 20.1 A on its SZ3046-3. Its parts list names T-Hobby's F7 35A/45A AIO and JHEMCU's GHF745 and GHF405 40A AIO boards. (MEPS spec table, MEPS 3800KV data test, MEPS product page)
- Props
- MEPS recommends 3.5-inch props such as the HQ3520 and tested the HQ3520-3 and its own SZ3046-3; props bolt to four M2 holes on a 5 mm circle. (MEPS product page, MEPS 2850KV data test, MEPS 3800KV data test, MEPS size chart)
- Battery
- 6S for the 2850KV, 4S for the 3800KV. (MEPS spec table)
- Frame
- Four M2 screws on a 9 mm circle (9 × 9 mm). (MEPS size chart, MEPS product page)
Where to buy
- MEPSthe maker's store; 1 motor in either KV and colour (the 2850KV Black+Gray marked sold out when checked), $63.60 for 4$15.90seen Oct 19, 2026Visit
Plain links, not affiliate links. Prices change; the store’s page has the current one.
Full specs
| Spec | Value | Source |
|---|---|---|
| KV | 2,850 rpm/V (also 3800KV) | MEPS spec table |
| Stator | 16 × 4 mm (1604) (from the size in MEPS's name) | MEPS product page |
| Configuration | 12N14P (12 stator slots, 14 magnet poles) | MEPS spec table |
| Battery | 6S LiPo (2850KV); 4S (3800KV) (MEPS's buying guide says the motor supports 3S–6S) | MEPS spec table |
| Weight | 12 g (with cable, both KVs) | MEPS spec table |
| Dimensions | φ20.92 × 15.5 mm (with shaft); body 12.6 mm tall | MEPS spec table, MEPS size chart |
| Shaft | 1.5 mm steel, protrudes 2.9 mm; T-mount with 4 × M2 holes on a 5 mm circle in the top | MEPS spec table, MEPS size chart, MEPS product page |
| Mounting | 4 × M2 holes on a 9 mm circle (MEPS's text calls it 9 × 9 mm) | MEPS size chart, MEPS product page |
| Bell | hollow CNC-machined aluminium, integrated housing | MEPS product page |
| Internal resistance | 252 mΩ (153 mΩ for 3800KV) | MEPS spec table |
| Idle current | 0.6 A (at 10 V; 0.75 A for 3800KV) | MEPS spec table |
| Peak current | 14.8 A (MEPS's "Peak Current (60S)", the full-throttle row of its HQ3520-3 test at 25.2 V; 18.7 A for 3800KV, its HQ3520-3 test at 16.8 V) | MEPS spec table |
| Max power | 368 W (MEPS's buying guide; 24.9 V × 14.8 A in its data test. 3800KV: 310.5 W on its HQ3520-3 test (S5). The spec table gives 196 W and 168 W (see modelNotes)) | MEPS product page, MEPS 2850KV data test |
| Leads | 24 AWG, 120 mm, with 8 mm of heat-shrink and 4 mm stripped ends | MEPS spec table, MEPS size chart |
Bench data
Redrawn from MEPS’s test reports. Thrust is static pull on a bench, more than you get in flight. Power is volts × amps; efficiency is thrust divided by power.
2850KV on 6S, 25.2 V1 prop
| Prop | Throttle | Voltage (V) | Current (A) | RPM | Thrust (g) | Efficiency (g/W) |
|---|---|---|---|---|---|---|
| HQ3520-3 (HQProp 3520, 3-blade) | 10% | 25.2 | 0.2 | 6872 | 13.8 | 2.54 |
| 20% | 25.2 | 0.7 | 12865 | 51.9 | 3.02 | |
| 30% | 25.2 | 1.5 | 18416 | 111.4 | 2.99 | |
| 40% | 25.2 | 2.7 | 23527 | 187.8 | 2.78 | |
| 50% | 25.1 | 4.3 | 27729 | 269.6 | 2.49 | |
| 60% | 25.1 | 6.1 | 31380 | 346 | 2.27 | |
| 70% | 25.1 | 7.8 | 34047 | 410.9 | 2.1 | |
| 80% | 25 | 10 | 37183 | 496.9 | 1.98 | |
| 90% | 25 | 12.4 | 39306 | 562.8 | 1.81 | |
| 100% | 24.9 | 14.8 | 40692 | 611.4 | 1.65 |
Source: MEPS 2850KV data test
3800KV on 4S, 16.8 V2 props
| Prop | Throttle | Voltage (V) | Current (A) | RPM | Thrust (g) | Power (W) | Efficiency (g/W) |
|---|---|---|---|---|---|---|---|
| HQ3520-3 (HQProp 3520, 3-blade) | 10% | 16.8 | 0.3 | 6247 | 11.3 | 5.1 | 2.24 |
| 20% | 16.8 | 0.9 | 11819 | 43.2 | 15.3 | 2.83 | |
| 30% | 16.8 | 1.8 | 16813 | 92.5 | 30.6 | 3.02 | |
| 40% | 16.8 | 3.2 | 21201 | 152.6 | 53.6 | 2.85 | |
| 50% | 16.8 | 5.1 | 25219 | 223.4 | 85.8 | 2.6 | |
| 60% | 16.7 | 7 | 28324 | 283.6 | 117.9 | 2.41 | |
| 70% | 16.7 | 9.2 | 31266 | 347 | 153.7 | 2.26 | |
| 80% | 16.7 | 11.7 | 34060 | 414.3 | 194.5 | 2.13 | |
| 90% | 16.6 | 14.6 | 36613 | 481.2 | 243.3 | 1.98 | |
| 100% | 16.6 | 18.7 | 38060 | 520.2 | 310.5 | 1.68 | |
| SZ3046-3 (MEPS SZ3046, 3-blade) | 10% | 16.8 | 0.3 | 5618 | 14.3 | 5.2 | 2.77 |
| 20% | 16.8 | 1 | 10241 | 48.8 | 16.9 | 2.9 | |
| 30% | 16.8 | 2.2 | 14129 | 93.9 | 37 | 2.54 | |
| 40% | 16.8 | 3.8 | 17450 | 144.3 | 64.6 | 2.24 | |
| 50% | 16.8 | 5.8 | 20522 | 194.3 | 97.3 | 2 | |
| 60% | 16.7 | 8.4 | 23630 | 258 | 141.1 | 1.83 | |
| 70% | 16.7 | 11.7 | 26685 | 331.2 | 195.1 | 1.7 | |
| 80% | 16.6 | 14.4 | 28340 | 377.2 | 239.6 | 1.57 | |
| 90% | 16.6 | 17.1 | 29882 | 415.2 | 284.7 | 1.46 | |
| 100% | 16.6 | 20.1 | 30825 | 441.6 | 332.6 | 1.33 |
Source: MEPS 3800KV data test
Inside the motor
A brushless outrunner: the coils stand still in the middle and the magnets spin around them. From the top down:
- Bell. Hollow CNC-machined aluminium in one piece with the housing, grey with a dark grey ("Black+Gray") or red ("Red+Gray") top cut into five slotted spokes. (MEPS product page, MEPS photo)
- Shaft. 1.5 mm steel, standing 2.9 mm above the bell, with four M2 holes on a 5 mm circle for T-mount props. (MEPS product page, MEPS size chart)
- Base. Four M2 holes on a 9 mm circle. (MEPS size chart)
- Leads. 24 AWG, 120 mm, with 8 mm of heat-shrink and 4 mm stripped ends. (MEPS spec table, MEPS size chart)
How fast it spins
KV is the motor’s no-load speed per volt. With nothing on the shaft, the 2850KV version reaches about these speeds; a prop loads the motor and brings it down, typically to around 70–75% of these figures at full throttle.
| Battery | Volts | No-load rpm (KV × V) | Electrical frequency | ESC steps per second |
|---|---|---|---|---|
| 4S nominal | 14.8 | 42,180 | 4,921 Hz | 29,526 |
| 4S full | 16.8 | 47,880 | 5,586 Hz | 33,516 |
| 6S nominal | 22.2 | 63,270 | 7,382 Hz | 44,289 |
| 6S full | 25.2 | 71,820 | 8,379 Hz | 50,274 |
A 14-pole rotor has 7 pole pairs, so every turn of the shaft is 7 electrical cycles, and a six-step ESC switches the phases 42 times per turn.
About the 3D model
A generic outrunner drawn from MEPS’s published sizes: the 16 × 4 mm stator, 20.92 mm bell, 12.6 mm height, 1.5 mm shaft, 9 mm mounting circle and 12 teeth and 14 magnets. Anything MEPS doesn’t publish is typical for a motor this size, and the bell’s spoked top, the base and the inside are a generic design, not this motor’s. The colours are read off the maker’s product photos. There are no logos or markings: it is our drawing, not the maker’s.
Sources
- MEPS: SZ1604 Lightweight Brushless Motor for 3.5" Freestyle FPV Drone 2850KV/3800KV (product page with buying guide, MEPS's own store). Retrieved Oct 19, 2026.
- MEPS: SZ1604 specification table for 2850KV and 3800KV (image on the product page; its max powers don't fit the data tests, see modelNotes). Retrieved Oct 19, 2026.
- MEPS: SZ1604 size chart (image on the product page). Retrieved Oct 19, 2026.
- MEPS: SZ1604 KV2850 data test, 10–100% throttle with an HQ3520-3 at 25.2 V, and thrust chart (image on the product page). Its power column is left out (see modelNotes).. Retrieved Oct 19, 2026.
- MEPS: SZ1604 KV3800 data test, 10–100% throttle with SZ3046-3 and HQ3520-3 props at 16.8 V, and thrust chart (image on the product page). Retrieved Oct 19, 2026.
- MEPS: SZ1604 2850KV Black+Gray main product photo, used for finish and spoke count. Retrieved Oct 19, 2026.
