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In case you are 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 show you how to make an knowledgeable determination.
Additional Studying: New to FPV drones? Check out our newbie’s information.
Professional Tip: Betaflight has launched a brand new characteristic that enables powering a 4S quad with a 6S LiPo battery by lowering motor output.
Right here’s an inventory 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 as a consequence 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 perhaps up for debate):
- LOWER amp draw
- LESS voltage sag
- LONGER flight time
- MORE responsive and agile efficiency
Decrease Amp Draw?
One of the crucial 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 below 40A on 6S (at 25.2V).
Decrease amp draw leads to:
- Much less stress on the battery
- Lowered “voltage sag” all through the flight
- Much less vitality loss within the wires as a consequence of resistance, although that is usually 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 using decrease C score packs for a similar energy, probably saving prices by deciding on cheaper cells.
Nonetheless, to match the burden of a 4S battery, we regularly select decrease capability batteries, which may restrict the most discharge present, since battery capability is a consider most discharge present. So, larger C score packs may nonetheless be obligatory.
Max Discharge Present = C Score x Battery Capability
Responsiveness
Because of much less voltage sag below load, the motors preserve constant acceleration, enabling them to vary RPM extra quickly and persistently. This leads to an total extra responsive and agile plane. The quicker RPM change price considerably impacts the dealing with of your quad.
Increased Effectivity?
There’s a controversial idea {that a} 6S FPV drone presents 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. Due to this fact, theoretically, flight occasions ought to be corresponding to these of a 4S when flying on the similar 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 fashion) or utilizing bigger battery packs with larger vitality capability. Nonetheless, both strategy will inevitably influence 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 modifications 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 because of the decrease present within the system, which ends up in much less overheat and total larger effectivity. Nonetheless this profit may not be noticeable normally.
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). Nonetheless, in drone racing, race tracks usually characteristic quite a few turns and gates, requiring as a lot pilot ability 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 combos. This flexibility permits for extra strategic selections find the perfect steadiness between effectivity and efficiency primarily based on the particular 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 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 standard KV rated motor.
| 4S – KV | 5S – KV | 6S – KV | RPM (VxKV) |
| 2300 | 1840 | 1533 | 38640 |
| 2400 | 1920 | 1600 | 40320 |
| 2500 | 2000 | 1667 | 42000 |
| 2600 | 2080 | 1733 | 43680 |
| 2700 | 2160 | 1800 | 45360 |
| 2800 | 2240 | 1867 | 47040 |
| 2900 | 2320 | 1933 | 48720 |
| 3000 | 2400 | 2000 | 50400 |
| 3525 | 2382 | 2350 | 59220 |
With extra volts within the system, you may 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 truly barely larger equivalent to 2500KV.
As KV will increase, the torque score is claimed to lower. Nonetheless, from my observations, voltage sag is a extra influential issue, stopping you from reaching the theoretical max RPM on 4S. That is perhaps 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 had 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, they usually did present brutal straight-line pace and spectacular cornering. Nonetheless, the downsides had been vital: 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 may simply get broken.
Nonetheless, Betaflight presents 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 rely and voltage of 5S are in between these of 4S and 6S, so you may anticipate its efficiency to even be intermediate. Nonetheless, 4S and 6S batteries are extra broadly obtainable, making 5S batteries comparatively uncommon.
Conclusion
Personally, I favor 6S largely 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 transferring up in voltage. Perhaps sooner or later, 8S and even 12S will grow to be 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 operating 6S on 4S motors
- Dec 2023 – up to date article
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