Choosing among FPV radios & batteries can mean solving two different problems: selecting an ExpressLRS receiver with the right control layout, or finding an AC charger for a DJI FPV battery. The practical shortcut is to match the component to the job first-channel capacity, fixed-wing use, signal-related features, or charging voltage-then use price as a tie-breaker.
Quick take
Start by separating receiver hardware from charging hardware. The three RadioMaster entries are ExpressLRS receivers, while the DJI entry is an AC power adapter and charger. Within the receivers, compare channel capacity and signal-focused attributes. If the need is charging, the receiver comparison is not the deciding factor; the CDX170-90 model and its power specifications are.
- RadioMaster ER4: Compact receiver hardware for smaller models and four PWM channels.
- RadioMaster ER8: Fixed-wing receiver supporting eight servos.
- RadioMaster RP3 V2: Receiver with antenna diversity, a built-in TCXO, and WiFi updates.
- Genuine DJI CDX170-90: AC charger and power adapter for a DJI FPV drone battery.
Listed-price comparison
The listed prices span USD 17.49 to USD 40.99, an absolute spread of USD 23.50.
| Product | Listed price | Price bar |
|---|---|---|
| RadioMaster ER4 ExpressLRS Receiver | USD 17.49 | |
| RadioMaster ER8 ExpressLRS Receiver | USD 40.99 | |
| RadioMaster RP3 V2 ExpressLRS Receiver | USD 22.49 | |
| Genuine DJI FPV Battery Charger CDX170-90 | USD 29.99 |
Decision matrix
- Four PWM channels for small aircraft, boats, or cars: RadioMaster ER4 ExpressLRS Receiver.
- A fixed-wing setup supporting eight servos: RadioMaster ER8 ExpressLRS Receiver.
- A receiver with antenna diversity, built-in TCXO, and WiFi updates: RadioMaster RP3 V2 ExpressLRS Receiver.
- A DJI FPV battery charger and AC adapter with 25.2V, 3.4A, and 86W output: Genuine DJI CDX170-90.
Product notes
RadioMaster ER4 ExpressLRS Receiver
At USD 17.49, the RadioMaster ER4 is a practical match for a compact ExpressLRS receiver role. Its description names small aircraft, boats, cars, high-speed response, flexible configuration, and four simultaneous PWM channels. That combination gives it a concrete reason to choose when the build centers on a smaller model and straightforward PWM control. The limitation is its component role: ER4 is a receiver rather than charging hardware or a battery. If four PWM channels are enough, its compact design keeps the decision focused on receiver functions instead of adding a charger to the comparison.
RadioMaster ER8 ExpressLRS Receiver
At USD 40.99, the RadioMaster ER8 is the receiver to consider when its eight-servo support is relevant. The description also lists DC 4.5-8.4V power, a 20cm high-sensitivity antenna, and a 43x30x15mm, 16.5g format. Those specifications give the buyer useful context beyond the channel count. Its limitation is physical planning: the listed dimensions and weight need to fit the intended airframe, and the unit remains a receiver rather than a charger or battery. Choose it when the fixed-wing, multi-servo brief is real; otherwise, its additional channel capacity may not be central to the job.
RadioMaster RP3 V2 ExpressLRS Receiver
At USD 22.49, the RP3 V2 brings a signal-focused set of details: LNA and PA components, two antennas, ExpressLRS firmware, and WiFi updates. Those attributes provide a concrete reason to choose it when receiver-side signal hardware and update convenience are priorities. The limitation is the stated working voltage of DC 5V, which makes the surrounding power arrangement part of the decision. RP3 V2 remains a receiver, so it does not replace a transmitter, battery, or charger. Its 2.404-2.479GHz frequency range and 500Hz/F1000Hz refresh figures are useful identifiers, but they should be read as specifications rather than automatic performance rankings.
Genuine DJI FPV Drone Battery Charger CDX170-90
At USD 29.99, the Genuine DJI FPV Drone Battery Charger AC Power Adapter CDX170-90 is the charging-focused choice. The title specifies 25.2V, 3.4A, and 86W, while the description lists 100-240V input and says a power cord is included. That makes it relevant for a shopper seeking the charger and adapter role named in the title rather than an ExpressLRS receiver. Its limitation is equally concrete: it is charging hardware, so it does not address receiver-channel needs such as PWM control or antenna diversity. The CDX170-90 model phrase is useful when matching the adapter to the DJI FPV setup.
Final recommendation by use case
- For a four-channel receiver used with smaller models: choose the RadioMaster ER4 ExpressLRS Receiver.
- For a fixed-wing receiver brief involving eight servos: choose the RadioMaster ER8 ExpressLRS Receiver.
- For antenna diversity and a built-in TCXO: choose the RadioMaster RP3 V2 ExpressLRS Receiver.
- For the AC charging role named by the product title: choose the Genuine DJI FPV Drone Battery Charger CDX170-90.
The component type should decide before price: the RadioMaster entries serve receiver duties, while the DJI model serves charging duties.
