How to Choose a 4-in-1 ESC: Current Rating, Voltage, Size and Firmware

A 4-in-1 ESC puts the four motor controllers of a quadcopter on one board, usually stacked under the flight controller. Choosing one comes down to four checks, in this order: the battery voltage it accepts, the continuous current per motor, the mounting size, and the firmware. Get the first two right and the board will survive; get the last two right and it will fit and fly well.

4-in-1 ESC shortlist

The table groups boards by the drone they suit. All ratings are per motor channel, as published by each maker. Match the voltage row to your battery before comparing amps.

Step 1: Match the battery voltage

Voltage is a hard limit. A battery voltage higher than the ESC is built for can destroy it, and a higher amp rating does not make a board safe on a bigger pack. Count cells, not nominal volts: a LiPo cell is 4.2 V when full, so 4S is 16.8 V, 6S is 25.2 V and 8S is 33.6 V at the start of every flight.

Read the input range on the maker's page, then check the rest of the power system against the same pack. The Foxeer Reaper F4 Mini, for example, is specified for DC 9–40 V, which covers 3–8S. The GEPRC TAKER H60 and GEP-BLS60A stop at 6S; the TAKER H65 8S and BrotherHobby Returner 4-8S go to 8S; the BrotherHobby 6-12S boards start at 6S and run up to 12S.

Watch for listings that contradict themselves. The Holybro Tekko32 F4 60A page gives 4–6S in its specification table and 3–6S in its description, so confirm the lower limit with the maker if you plan a 3S build.

Step 2: Size the continuous current

The number on a 4-in-1 ESC is per motor. A "60A" board can feed each of its four motors 60 A continuously, not 60 A shared between them. Each board also has a burst rating for short peaks; makers that state its duration give it in seconds, typically 5 to 10.

• GEPRC GEP-BLS60A-4IN1: 60A continuous, 65A burst for 5 seconds.
• GEPRC TAKER H65 8S: 65A continuous, 70A burst for 5 seconds.
• BrotherHobby Returner 65A V3 PRO: 65A continuous, 75A for 10 seconds.
• BrotherHobby Returner 4-8S 70A PRO: 70A continuous (rated at 6S), 80A for 10 seconds.
• HOBBYWING XRotor FPV G2 45A: 45A continuous, 60A peak, with no duration stated.

Compare continuous ratings first. A burst figure without a duration tells you little.

Then compare against the motor. The ESC must handle the current your motor and propeller draw at full throttle on your battery, and an amp rating can never be too high, only too low. The only extra cost of a bigger board is weight, which matters on light builds.

Worked example: 5-inch on 6S

The GEPRC SPEEDX2 2207 lists a maximum current of 52.2 A for the 1960KV version and 56 A for the 2050KV version on 6S. A 55A board covers the first with little margin; a 60–65A board covers both. The Axisflying AE2207 V2 1960KV lists 38.65 A, so a 45A board would technically be enough. A 55–65A board still makes sense: lower-rated ESCs are more easily damaged in crashes and by voltage spikes, and the extra rating costs only a few grams.

Two motors with the same size and KV can publish very different maximum currents, because makers test with different propellers. Use the figure measured on the propeller you will fly, and treat a test on another propeller as a rough guide only.

Worked example: 7-inch on 6S

The FlashHobby A2807 1300KV lists a peak current of 37.91 A over 60 seconds on 6S, measured with a 7 × 3.5 inch tri-blade propeller. A 45A board would cover it. A 55–65A 30.5 mm board gives comfortable headroom.

What the battery can actually deliver

Four SPEEDX2 2207 2050KV motors at their listed maximum would draw 4 × 56 = 224 A. Few 5-inch packs can sustain that, and in normal flying each motor draws far less than its rated maximum. That is why a 55–65A board rarely runs near its limit on a 5-inch quad. It does not make an undersized board safe. Racing builds that run long full-throttle sections are the case where the ESC rating needs the closest attention.

Step 3: Choose the mounting size

• 30.5 × 30.5 mm: the standard for 5-inch and larger. Larger MOSFETs and solder pads mean more current headroom and easier soldering.
• 20 × 20 mm: lighter, for 3-inch and 4-inch builds. These boards usually have lower current ratings and are generally less robust than 30.5 mm boards.
• 25.5 × 25.5 mm all-in-one boards combine the ESC and flight controller. They suit sub-250 g builds, cinewhoops and toothpicks, where power demands are low.

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Check the outline as well as the hole pattern. The HOBBYWING XRotor G2 45A uses 20 × 20 mm holes in a 40 × 33 mm board; the BrotherHobby Returner 65A V3 PRO uses 30.5 mm holes but measures 74 × 64.5 × 21.8 mm and carries two external 1,500 µF capacitors, so it needs a roomy frame. The 12S BrotherHobby boards measure 104 × 64 mm and weigh 143 g.

If the ESC and flight controller come from different brands, check the connector pinout before plugging in the harness. Pinouts often differ, and a mismatched harness can damage both boards. Buying a matched stack avoids the problem.

Step 4: Choose 4-in-1 or single ESCs

A 4-in-1 board means fewer solder joints, a cleaner build and the weight centred in the frame. Its drawback is that one failed channel means replacing the whole board, although failures are now rare on boards from established brands.

Single ESCs control one motor each and sit on the arms. Each can be replaced on its own and they spread heat, but they need a power distribution board or a flight controller with power distribution, plus more wiring. Today they are mostly used on large frames, such as builds with the GEPRC TAKER S80 or S100 (80A and 100A continuous, 3–8S).

Step 5: Choose the firmware

• BLHeli_S: firmware for 8-bit boards. The official version is no longer updated; flash Bluejay to get bidirectional DShot.
• Bluejay: open-source successor to BLHeli_S for compatible 8-bit boards, actively maintained, with bidirectional DShot.
• AM32: open-source firmware for 32-bit ARM boards (STM32, AT32 and others), actively maintained, with bidirectional DShot.
• BLHeli_32: closed-source 32-bit firmware, no longer in development; bidirectional DShot from version 32.7.0.

Bluejay is flashed onto BLHeli_S-compatible boards and adds bidirectional DShot, selectable 24, 48 or 96 kHz PWM and DShot 150, 300 and 600. AM32 runs on 32-bit ARM processors, supports DShot 300 and 600 and bidirectional DShot, and can be updated through a Betaflight flight controller.

In practice a Bluejay-flashed 8-bit board and an AM32 board perform about the same, so price, size and availability can decide. "BLS" in a product name, as on the GEPRC TAKER and HAKRC boards, means BLHeli_S hardware. The board can usually take Bluejay, but check that your exact board target is supported before flashing.

Two firmware details matter for buyers. AM32 does not list DShot150, so run Betaflight at a 4 kHz or 8 kHz loop with DShot300 or DShot600. And AM32 can be flashed onto BLHeli_32 boards but is not easily reversed, so do not flash stock you may need to return.

Step 6: Plan the capacitor and power wiring

Solder a low-ESR electrolytic capacitor to the ESC's battery pads, even if the board already carries small filter capacitors. It absorbs voltage spikes and reduces electrical noise in the video, the gyro and the rest of the power system.

Choose a voltage rating of 1.5–2 times the full pack voltage, because spikes run well above the battery voltage:

• 4S (16.8 V full): 25 or 35 V.
• 6S (25.2 V full): 35 or 50 V.
• 8S (33.6 V full): 50 or 63 V.

For capacitance, a 5-inch build typically uses 680–1,000 µF and a 6–7 inch build 1,000–2,200 µF. Two smaller capacitors in parallel work as well and are easier to fit. Mount the capacitor as close to the pads as possible; the longer leg is positive.

Many boards ship with one. The Holybro Tekko32 F4 60A includes a 1,000 µF 35 V capacitor and Holybro strongly recommends fitting it on 6S. The BrotherHobby 6-12S boards come with a 680 µF 63 V capacitor, and the BrotherHobby 4-8S 70A PRO lists a 1,500 µF 50 V capacitor. GEPRC includes a capacitor with the TAKER H60, H65 and GEP-BLS60A but does not publish its rating, so check the printed rating before using it at 8S.

Setup and first power-up

• Check the pinout between ESC and flight controller, then check with a multimeter that the battery pads are not shorted.
• Power up the first time through a short-circuit protector, propellers off. The MAD KONKER unit trips at 3.5 A and accepts up to 30 V, which covers 2–6S packs but not 8S.
• In Betaflight, choose DShot to match the loop rate: DShot150 for 2 kHz, DShot300 for 4 kHz, DShot600 for 8 kHz. DShot needs no ESC calibration.
• Turn on bidirectional DShot and set the motor poles. Typical 5-inch motors have 14 magnets, the default; smaller motors often have 12. In the Motors tab, each motor should show RPM with an error rate below 1%.
• Set the current sensor scale from the ESC maker's figure (for example 120 on the Holybro Tekko32 F4 60A, 70 on the Foxeer Reaper F4 Mini) so the OSD shows true current draw and used capacity.
• If the flight controller depends on the ESC for power, confirm the BEC first. The BrotherHobby 6-12S boards list a 19 V 3 A BEC. The HOBBYWING XRotor G2 45A page lists no BEC output in one place and a 5 V BEC in another, so do not rely on it without checking the board.

Common mistakes

• Reading the headline amps as a total for the board. It is per motor.
• Comparing burst ratings without durations.
• Using a 6S board on 8S because the amp rating looks large.
• Buying a 20 × 20 mm board for a hard-hit 5-inch freestyle quad to save a few grams.
• Plugging a harness between brands without checking the pinout.
• Flashing AM32 or Bluejay without confirming the board target.
• Skipping the capacitor because the board "already has capacitors".

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