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 submit, I’ll clarify the variations and provide help 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 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% larger nominal voltage than a 4S attributable to two additional 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 may be up for debate):

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

Decrease Amp Draw?

One of the vital vital 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 leads to:

• Much less stress on the battery
• Decreased “voltage sag” all through the flight
• Much less power loss within the wires attributable to resistance, although that is typically 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 helpful for battery longevity. This additionally permits the usage of decrease C ranking packs for a similar energy, doubtlessly saving prices by choosing inexpensive cells.

Nevertheless, to match the load of a 4S battery, we frequently select decrease capability batteries, which might restrict the most discharge present, since battery capability is a think about most discharge present. So, larger C ranking packs may nonetheless be needed.

Max Discharge Present = C Ranking x Battery Capability

Responsiveness

As a consequence of much less voltage sag beneath load, the motors keep constant acceleration, enabling them to vary RPM extra quickly and constantly. This leads to an total extra responsive and agile plane. The quicker RPM change price considerably impacts the dealing with of your quad.

Greater Effectivity?

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

This isn’t essentially true, as we frequently 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 occasions must be similar to these of a 4S when flying on the identical velocity.

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

The profit in flight time is extra prone to be seen in AP (aerial pictures) platforms, the place motor velocity is extra constant, and speedy 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 larger effectivity. Nevertheless this profit won’t be noticeable typically.

Is 6S Quicker?

A 6S quadcopter, with specifically chosen elements, 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 characteristic quite a few turns and gates, requiring as a lot pilot ability 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 selections find the most effective steadiness between effectivity and efficiency based mostly on the particular race monitor.

Selecting Motors for 6S

There are two sides to the argument when choosing motors for a 6S FPV drone. Some advocate decrease KV motors to match the theoretical max RPM of 4S-equivalent motors, whereas others counsel 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 standard KV rated motor.

With extra volts within the system, you may execute the KV extra successfully. The truth is, you may want even barely decrease KV than calculated to attain the identical RPM in flight. For instance, 1600KV on 6S may equate to not 2400KV on 4S, however really barely larger reminiscent of 2500KV.

As KV will increase, the torque ranking is alleged 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 seen the flexibility to swing a heavier prop extra successfully (e.g., larger 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 here are my motor suggestions.

Operating 6S LiPo on 4S Motors

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

These motors are thought of extremely excessive KV for 6S, and so they did present brutal straight-line velocity and spectacular cornering. Nevertheless, the downsides have been vital: extreme voltage sag and horrible inefficiency. The motors additionally turned 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 gives an answer to scale back motor output, which means that you can energy 4S quad with 6S LiPo by setting motor output to 66%.

How About 5S?

Effectively, the cell depend and voltage of 5S are in between these of 4S and 6S, so you may count on its efficiency to even be intermediate. Nevertheless, 4S and 6S batteries are extra extensively obtainable, making 5S batteries comparatively uncommon.

Conclusion

Personally, I desire 6S largely for the diminished voltage sag. Aside from that, I don’t really feel it’s considerably completely different from 4S in different facet. Oh, how many individuals nonetheless keep in mind the dialogue again in 2014/2015 after we have been deciding between 3S and 4S? It appears we’re nonetheless transferring up in voltage. Perhaps sooner or later, 8S and even 12S will turn into widespread – who is aware of? 🙂 Replace – Right here’s a brand new article discussing the opportunity 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 working 6S on 4S motors
• Dec 2023 – up to date article