In case you are simply beginning out with 5-inch FPV drones, you would possibly discover it difficult to determine whether or not to make use of a 4S or 6S LiPo battery. On this publish, I’ll clarify the variations and make it easier to make an knowledgeable determination.

A number of the hyperlinks on this web page are affiliate hyperlinks. I obtain a fee (at no further price to you) if you happen to make a purchase order after clicking on one in all these affiliate hyperlinks. This helps assist the free content material for the neighborhood on this web site. Please learn our Affiliate Hyperlink Coverage for extra data.

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

Professional Tip: Betaflight has launched a brand new characteristic that permits powering a 4S quad with a 6S LiPo battery by decreasing 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% greater nominal voltage than a 4S as a result of 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 embody (a few of these factors is likely to 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 practically 60A on 4S (at 16.8V) whereas it’s solely beneath 40A on 6S (at 25.2V).

Decrease amp draw ends in:

• Much less stress on the battery
• Diminished “voltage sag” all through the flight
• Much less power loss within the wires as a result of resistance, although that is usually negligible

Take a look at 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 using decrease C ranking packs for a similar energy, doubtlessly saving prices by deciding on inexpensive cells.

Nevertheless, to match the load of a 4S battery, we regularly select decrease capability batteries, which may restrict the most discharge present, since battery capability is a think about most discharge present. So, greater C ranking packs would possibly nonetheless be crucial.

Max Discharge Present = C Score x Battery Capability

Responsiveness

Resulting from much less voltage sag beneath load, the motors preserve constant acceleration, enabling them to alter RPM extra quickly and constantly. This ends in an general extra responsive and agile plane. The sooner RPM change fee considerably impacts the dealing with of your quad.

Greater Effectivity?

There’s a controversial principle {that a} 6S FPV drone presents longer flight instances 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 realize related speeds on a 6S, the motors must spin at comparable RPMs, requiring the same quantity of energy. Due to this fact, theoretically, flight instances ought to be akin to these of a 4S when flying on the similar velocity.

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

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

However why are there individuals claiming they’re getting longer flight time on 6S than 4S? Possibly it’s because of the decrease present within the system, which ends up in much less overheat and general greater effectivity. Nevertheless this profit won’t be noticeable usually.

Is 6S Quicker?

A 6S quadcopter, with specifically chosen elements, definitely 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 usually characteristic quite a few turns and gates, requiring as a lot pilot talent as uncooked velocity, if no more.

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

Selecting Motors for 6S

There are two sides to the argument when deciding on motors for a 6S FPV drone. Some suggest decrease KV motors to match the theoretical max RPM of 4S-equivalent motors, whereas others recommend utilizing related KV motors as on 4S to completely 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. The truth is, you would possibly want even barely decrease KV than calculated to realize the identical RPM in flight. For instance, 1600KV on 6S would possibly equate to not 2400KV on 4S, however really barely greater corresponding to 2500KV.

As KV will increase, the torque ranking 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 is likely to be why some individuals declare 6S really feel “extra punchy”.

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

Listed below are my motor suggestions.

Working 6S LiPo on 4S Motors

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

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

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

How About 5S?

Properly, the cell depend and voltage of 5S are in between these of 4S and 6S, so you possibly can count on its efficiency to even be intermediate. Nevertheless, 4S and 6S batteries are extra broadly accessible, making 5S batteries comparatively uncommon.

Conclusion

Personally, I choose 6S principally for the decreased voltage sag. Other than that, I don’t really feel it’s considerably completely different from 4S in different side. Oh, how many individuals nonetheless keep in mind the dialogue again in 2014/2015 once we have been deciding between 3S and 4S? It appears we’re nonetheless shifting up in voltage. Possibly sooner or later, 8S and even 12S will develop into widespread – 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