Choosing among FPV radios & batteries can feel like comparing parts that solve different problems: three entries are ExpressLRS receivers, while one is a battery-and-charger set for named Sky Viper aircraft. The useful shortcut is to start with your model and control layout. Need four PWM channels, support for eight servos, antenna diversity, or a 750mAh battery set? Here is how the four choices separate without treating a receiver and a battery as interchangeable.
Quick take
- Four-channel control: Choose the RadioMaster ER4 ExpressLRS receiver for small aircraft, boats, cars, and other models needing four simultaneous PWM channels.
- Eight-servo fixed-wing control: The RadioMaster ER8 ExpressLRS receiver is the direct match for its stated eight-channel and fixed-wing role.
- Signal-focused features: The RadioMaster RP3 V2 ExpressLRS receiver centers on antenna diversity, a built-in TCXO, LNA, PA, and WiFi updates.
- Named Sky Viper aircraft: The Battery & Charger Set 750mAh is the relevant choice when your aircraft is among the Sky Viper models named with it.
Listed-price comparison
The four listed prices run from USD 12.00 to USD 40.99, an absolute spread of $28.99. Price alone does not settle the choice because the set is a different type of accessory from the three receivers.
| Product | Listed price | Price bar |
|---|---|---|
| RadioMaster ER4 ExpressLRS 4-Channel Receiver | USD 17.49 | |
| RadioMaster ER8 ExpressLRS 8-Channel Receiver | USD 40.99 | |
| RadioMaster RP3 V2 ExpressLRS Receiver | USD 22.49 | |
| Sky Viper 750mAh Battery & Charger Set | USD 12.00 |
Decision matrix
| Need | Match | Deciding detail | What to weigh |
|---|---|---|---|
| Four PWM channels | RadioMaster ER4 | Small aircraft, boats, cars, and compact design | Four-channel designation |
| Eight servos in fixed-wing use | RadioMaster ER8 | Fixed-wing focus and eight-channel support | 43×30×15mm size and 16.5g weight |
| Antenna diversity and signal features | RadioMaster RP3 V2 | Built-in TCXO, LNA, PA, and WiFi updates | DC 5V working voltage |
| Sky Viper battery-and-charger need | 750mAh Battery & Charger Set | Named Sky Viper aircraft and combined set | It addresses battery power rather than receiver control |
Product notes
RadioMaster ER4 ExpressLRS 4-Channel Receiver
RadioMaster ER4 is the clearest match for a small aircraft, boat, car, or other model that needs four simultaneous PWM channels. The ExpressLRS 2.4GHz receiver pairs that channel count with a compact design, high-speed response, and flexible configuration, giving it a defined role in a compact control setup. Its concrete limitation is the four-channel designation: a fixed-wing build organized around eight servos points toward the ER8 instead. Choose ER4 when the four-channel wording in its title matches your control plan; move on when the airframe's stated requirement is eight channels.
RadioMaster ER8 ExpressLRS 8-Channel Receiver
RadioMaster ER8 is the fit for fixed-wing setups that need support for eight servos. A practical reason to choose it is that fixed-wing focus, with a 20cm high-sensitivity antenna and a 4.5-8.4V power supply also specified. The limitation is physical planning: the stated 43×30×15mm size and 16.5g weight are details to account for in the airframe. If your setup is built around four PWM channels rather than eight servos, the ER8's defining channel count is not the direct match. It makes sense when the fixed-wing brief calls for the eight-channel receiver named in its title.
RadioMaster RP3 V2 ExpressLRS Receiver
The RP3 V2 offers a feature-led receiver choice: its ExpressLRS design includes antenna diversity, a built-in TCXO, LNA, PA, and WiFi updates. Those details give it a clear place in demanding FPV and long-range performance setups. Its limitation is the stated DC 5V working voltage, which makes power specification a central fit question for the build. The title identifies it as a receiver, not a battery or charger, so it belongs on the control-signal side of the shopping list. Pick RP3 V2 when its signal and update features matter more than matching a four- or eight-channel layout.
Sky Viper 750mAh Battery & Charger Set
The Battery & Charger Set combines a 750mAh battery with a charger and is named for Sky Viper s1700, s1750, FURY V2400HD, V2450FPV, V2450GPS, SCOUT, and JOURNEY aircraft. That specific aircraft fit is the concrete reason to choose it, while the product description also identifies the battery as high-discharge and high-power. The limitation is scope: its title is tied to those Sky Viper models, while the other entries are ExpressLRS receivers. Choose it when the aircraft name on your project matches the title; if you need receiver hardware, compare the three RadioMaster designs instead.
Final recommendation by use case
- Small aircraft, boats, or cars: Choose the RadioMaster ER4 ExpressLRS 4-Channel Receiver; its title and compact-model description align directly with that use.
- Fixed-wing layouts using eight servos: Choose the RadioMaster ER8 ExpressLRS 8-Channel Receiver, whose title states the relevant channel count.
- Demanding or long-range FPV applications: Choose the RadioMaster RP3 V2 ExpressLRS Receiver for its listed antenna diversity and built-in TCXO.
- Named Sky Viper aircraft: Choose the Battery & Charger Set 750mAh because it combines the battery and charger around the aircraft names listed in its title.
The $28.99 price spread is meaningful, but fit should lead the decision: channel layout for ER4 or ER8, signal-oriented features for RP3 V2, and aircraft-specific battery use for the Sky Viper set.
