6S vs 4S LiPo for FPV Drones: Which Battery Voltage is Higher for Effectivity and Efficiency

If you’re simply beginning out with 5-inch FPV drones, you may discover it difficult to resolve whether or not to make use of a 4S or 6S LiPo battery. On this put up, I’ll clarify the variations and assist you to make an knowledgeable determination.

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Additional Studying: New to FPV drones? Check out our newbie’s information.

Professional Tip: Betaflight has launched a brand new function that enables powering a 4S quad with a 6S LiPo battery by lowering motor output.

Right here’s a listing of my favorite 6S and 4S LiPo batteries.

Advantages of 6S Over 4S

A 6S LiPo battery has a 50% increased nominal voltage than a 4S attributable to two further cells. The utmost voltage of a 6S is as much as 25.2V, in comparison with 16.8V for a 4S.

The potential enhancements from utilizing a 6S over a 4S embrace (a few of these factors may be up for debate):

• LOWER amp draw
• LESS voltage sag
• LONGER flight time
• MORE responsive and agile efficiency

Decrease Amp Draw?

Some of the important benefits of 6S over 4S is the decrease present required to provide the identical energy.

Energy is voltage multiplied by present: P = V x I

For instance, to provide 1000W, it takes almost 60A on 4S (at 16.8V) whereas it’s solely beneath 40A on 6S (at 25.2V).

Decrease amp draw leads to:

• Much less stress on the battery
• Diminished “voltage sag” all through the flight
• Much less vitality loss within the wires attributable to resistance, although that is typically negligible

Try some DVR footage of a 6S quad:

Is 6S Higher for Your Battery?

The decrease amp draw means your batteries run cooler throughout flight, which is useful for battery longevity. This additionally permits the usage of decrease C score packs for a similar energy, doubtlessly saving prices by choosing cheaper cells.

Nevertheless, to match the load of a 4S battery, we regularly select decrease capability batteries, which might restrict the most discharge present, since battery capability is a consider most discharge present. So, increased C score packs may nonetheless be essential.

Max Discharge Present = C Score x Battery Capability

Responsiveness

Resulting from much less voltage sag beneath load, the motors keep constant acceleration, enabling them to vary RPM extra quickly and persistently. This leads to an total extra responsive and agile plane. The sooner RPM change charge considerably impacts the dealing with of your quad.

Greater Effectivity?

There’s a controversial idea {that a} 6S FPV drone provides longer flight occasions than a 4S.

This isn’t essentially true, as we regularly choose 6S batteries of comparable weight or watt-hours (Wh) as 4S batteries. To attain related speeds on a 6S, the motors have to spin at comparable RPMs, requiring an analogous quantity of energy. Subsequently, theoretically, flight occasions needs to be similar to these of a 4S when flying on the identical pace.

Longer flight occasions with a 6S are potential by lowering motor energy (e.g., utilizing lighter props or adapt a much less aggressive flying model) or utilizing bigger battery packs with increased vitality capability. Nevertheless, both method will inevitably impression plane efficiency.

The profit in flight time is extra more likely to be seen in AP (aerial pictures) platforms, the place motor pace is extra constant, and fast RPM adjustments like these in racing drones are much less frequent.

However why are there folks claiming they’re getting longer flight time on 6S than 4S? Perhaps it’s as a result of decrease present within the system, which results in much less overheat and total increased effectivity. Nevertheless this profit won’t be noticeable normally.

Is 6S Quicker?

A 6S quadcopter, with specifically chosen parts, actually have some benefit over a 4S (as demonstrated by {most professional} racers have now switched from 4S over to 6S batteries). Nevertheless, in drone racing, race tracks typically function quite a few turns and gates, requiring as a lot pilot talent as uncooked pace, if no more.

The decrease present draw and decrease voltage drop of 6S give racers extra room to experiment with motor and prop mixtures. This flexibility permits for extra strategic decisions find one of the best steadiness between effectivity and efficiency based mostly on the precise race monitor.

Selecting Motors for 6S

There are two sides to the argument when choosing motors for a 6S FPV drone. Some suggest decrease KV motors to match the theoretical max RPM of 4S-equivalent motors, whereas others counsel utilizing related KV motors as on 4S to totally make the most of the additional energy from 6S batteries.

I’ll experiment with each concepts in my testing.

Decrease KV Motors

For a safer and extra environment friendly setup, select a low KV motor that gives a theoretical max RPM in the identical vary as an equal 4S setup utilizing a typical KV rated motor.

With extra volts within the system, you possibly can execute the KV extra successfully. Actually, you may want even barely decrease KV than calculated to realize the identical RPM in flight. For instance, 1600KV on 6S may equate to not 2400KV on 4S, however really barely increased akin to 2500KV.

As KV will increase, the torque score is claimed to lower. Nevertheless, from my observations, voltage sag is a extra influential issue, stopping you from reaching the theoretical max RPM on 4S. That may be why some folks declare 6S really feel “extra punchy”.

With a 6S setup, I additionally observed the flexibility to swing a heavier prop extra successfully (e.g., increased pitch props). If I had been utilizing a 4S LiPo, most excessive KV motors wouldn’t have the ability to swing a heavy prop at excessive RPMs like on the 6S setup.

Listed here are my motor suggestions.

Operating 6S LiPo on 4S Motors

I examined 4S motors (2350KV) on 6S batteries.

These motors are thought-about extremely excessive KV for 6S, they usually did present brutal straight-line pace and spectacular cornering. Nevertheless, the downsides had been important: extreme voltage sag and horrible inefficiency. The motors additionally grew to become extraordinarily scorching after a brief flight. Personally I might keep away from utilizing 4S motors on 6S batteries, motors may simply get broken.

Nevertheless, Betaflight provides an answer to cut back motor output, which means that you can energy 4S quad with 6S LiPo by setting motor output to 66%.

How About 5S?

Nicely, the cell depend and voltage of 5S are in between these of 4S and 6S, so you possibly can anticipate its efficiency to even be intermediate. Nevertheless, 4S and 6S batteries are extra extensively out there, making 5S batteries comparatively uncommon.

Conclusion

Personally, I favor 6S principally for the lowered voltage sag. Other than that, I don’t really feel it’s considerably totally different from 4S in different side. Oh, how many individuals nonetheless bear in mind the dialogue again in 2014/2015 once we had been deciding between 3S and 4S? It appears we’re nonetheless shifting up in voltage. Perhaps sooner or later, 8S and even 12S will change into frequent – who is aware of? 🙂 Replace – Right here’s a brand new article discussing the potential of utilizing 8S Lipo in FPV drones in 2023: https://oscarliang.com/8s-fpv-drone-2023/

Edit Historical past

• Feb 2018 – article created
• Jan 2020 – added information about operating 6S on 4S motors
• Dec 2023 – up to date article