This is a review of the BetaFPV HX115 SE, a 3-inch Toothpick FPV drone powered by 1S LiPo battery. It’s very light weight, quiet and safe to fly in local parks, and yet it offers extremely high performance.
Where to Buy HX115 SE?
There’s only 1 RX protocol option – Frsky SPI (D8/D16).
- Banggood: https://oscarliang.com/product-q4tr
- BetaFPV: https://oscarliang.com/product-6it9
- GetFPV: https://oscarliang.com/product-ls28
- 1x HX115 SE Toothpick FPV Drone
- 1x 1S 450mAh LiPo Battery (BT2.0 connector)
- 2 sets of HQ 3020 bi-blade Props
You should get some spare props (3020 with 1.5mm holes): https://oscarliang.com/product-rggj
HX115 SE Specs
- Frame size: 115mm
- Motor: 1102 18000KV
- Propeller: HQ 3020 2-Blade Propellers 1.5mm Shaft
- Flight controller:F4 1S 12A AIO FC
- VTX: A01 25-200mW VTX
- Camera: Caddx ANT camera
- Camera Tilt Degree: 0-60°
- Receiver: SPI Frsky FCC D8/D16
- Battery connector: BT2.0
- Recommended Battery: BT2.0 450mAh 1S LiPo
- Weight without battery: 39.1g
The BetaFPV HX115 SE is in the same class as the famous KababFPV 1S 3″ toothpick. The main difference is that the HX115 SE uses smaller 1102 motors with 1.5mm shaft.
The quad alone weighs 39.1g, 51.4g with a 1S 450mAh LiPo.
The BetaFPV HX115 SE is shipped with a single 1S 450mAh LiPo battery with BT2.0 connector. They have better conductivity than the typical PH2.0 connectors used in 1S micro drones.
- To get more spare batteries: https://oscarliang.com/product-t30n
- You will need a charger with BT2.0 connectors: https://oscarliang.com/product-v5db
Normal LiPo should only be charged to 4.20V, but these batteries are LiHV, meaning they can be charged up to 4.35V.
When taking the canopy off, I found the nylon screws are extremely easy to strip. Eventually I replaced them with some steel ones, they are less than half a gram heavier. (1x M2 12mm, 2x M2 4mm)
The FPV camera and VTX are mounted separately inside the canopy. The camera is the Caddx Ant, image quality is pretty decent for a tiny camera this small and light weight. You can see the image quality comparison here. The radio receiver is integrated in the FC, which supports Frsky D8/D16 (ACCST V1).
Most of the 1S flight controllers on the market have only 5A ESC, but the new BetaFPV F4 1S Toothpick FC have integrated 12A ESC that’s capable of driving 3-inch propellers. FC product page: https://oscarliang.com/product-65ni
The F4 FC has two UART’s and they are both free for your disposal.
Since the FC has solder pads for motors, it’s entirely possible to upgrade the motors even if they don’t have connectors.
Two of the FC screws extrudes from the bottom and might dig into your battery, loosening those screws a tiny bit fixes it.
The HX115 SE is really quiet, you can barely hear it 30 meters away.
The power to weight ratio is absolutely insane due to the high KV motors, and pretty power hungry too if you fly aggressively. It hovers at 20% throttle and feels super light in the air. Although hover time can reach 5:30 with the provided 1S 450mAh LiPo, when you really punch that throttle, flight time can be drastically reduced to under 3-minute.
It’s got some oscillations in flight, wobbles quite a bit when it’s wind, and there’s prop wash when doing slit-S probably because the small motors and they lack torque. Above 70% throttle, there’s no noticeable change in RPM, the motors just can’t handle those 3″ props.
It handles much like a 2.5″ toothpick. Flight performance will definitely benefit from some further tuning on filters and PID. It appears they did attempt to tune the PID in factory, but I think there’s still room for improvement.
Range is around 200-300 meters, fairly typical for an integrated SPI receiver. If you want more range, I think the HX115 SE would be a great platform for the ExpressLRS 2.4GHz RF system. Not only it will give you decent rage (a couple of km easily), its 500Hz mode can drastically reduce control latency and make the quad feel more connected. UART 1 and 2 on the FC are both free for additional RX, as VTX SmartAudio is connected via Softserial.
How to Setup Betaflight HX115 SE
Board: BEFH/BETAFPVF411RX(STM32F411), it comes with firmware version 4.2.9. You can find CLI dump here.
First, binding RX to radio. To enter “bind mode”, in CLI, enter bind_rx.
In Modes tab, assign switches to arm, beeper, Flip Over After Crash.
- Set arming angle to 180
- Enable ESC Beacon (RX_SET only)
Power & Battery Tab:
- Minimum cell voltage: 2.9V
- Maximum cell voltage: 4.39V
- Warning cell voltage: 3.25V
Setup Rates and OSD screen to your preference.
That’s it, you are ready for first flight.
The ESC’s are using “Z-H-30” BLHeli_S firmware, 16.70. There doesn’t seem to be new firmware for this to enable RPM filter or 48KHz at the moment for this particular target.
I really like this 1S 3″ concept, it’s super quiet and flies amazingly. Also it’s pretty harmless compared to a full power 5″ quad. The OG KababFPV build might be the best right now in this class, but it’s always out of stock and especially difficult to get for non-American pilots, it would be great if there’re other alternatives.
The BetaFPV HX115 SE could have been that alternative if they use better motors and tuning.
It’s quite powerful for an 1S quad, perhaps a bit too much vibration, it could be a lot better if they try larger motors with lower KV, like 1202.5 11500KV, or the even wider 13mm motors that are recommended by KababFPV. The 1102 motors used here are considered slightly too small even for 2.5″ builds, of course they would lack the torque for 3″ props.
But I imagine upgrading the motors would probably also require upgrading the BT2.0 battery connector to XT30 in order to keep up with the increased current demand. XT30 is heavier, but it has less resistance than BT2.0. That means they would have to invest in making a whole new type of battery as they don’t currently offer 1S 450-600mAh LiPo with XT30 connectors. It’s going to be costly for them.
Update – Upgrading Motors
I tried to upgrade the motors to 1202.5 11500KV.
Note that the original motors use 3 screws.Although the frame has holes for the four-screw motors, they are slightly too close together, and don’t fit motors with 9mm diagonal mounting pattern. For the RekonFPV 1202.5 motors I am using, I can only fit 2 adjacent holes. This is clearly not ideal, but I am still doing this just to see how it performs. I will probably replace the frame later.
I am still using BT2.0 connector in this test.
It flies much better, much more locked in and throttle response also more linear. Flight time is slightly less, just above 2 minutes of aggressive flying. You can still cruise til 3 minutes mark, but it feels powerless and RPM doesn’t change much when you punch throttle. I think we just hit the limit of the BT2.0 connector and LiPo at the end of the pack.
Overall I think the larger motors are a worthy upgrade. I changed the PID.
My current PID:
set throttle_boost = 0 set p_pitch = 100 set i_pitch = 65 set d_pitch = 75 set f_pitch = 0 set p_roll = 100 set i_roll = 65 set d_roll = 70 set f_roll = 0 set p_yaw = 90 set i_yaw = 85 set f_yaw = 0 set d_min_roll = 20 set d_min_pitch = 22 set d_min_boost_gain = 27
Filters, move both Gyro and Dterms to the left two notches to get rid of excessive vibrations in flight.