Transferring up in battery cell depend has been an ongoing shift on the planet of FPV drones. In 2015, 4S overtook 3S as the usual. By 2018, 6S was all the fashion. Quick ahead to 2023, the thrill now revolves round a good greater voltage – 8S. When you’ve questioned why, you’re not alone. On this article, I’ll delve into the explanations behind this pattern, discussing the advantages and downsides of utilizing 8S batteries, and assist you to decide if constructing an 8S drone in 2023 is an efficient excellent.
When discussing 8S, we’re referring to the variety of cells in a LiPo battery, which decide the battery voltage. To study extra concerning the fundamentals, check out my LiPo battery tutorial.
What Do You Want To Fly 8S?
Battery
Able to take the leap to 8S? You possibly can procure 8S LiPo batteries right here: https://oscarliang.com/product-voun
Charger
Remember, most Lipo chargers in the marketplace solely assist as much as 6S, so an 8S-supporting charger shall be a crucial funding:
Motors
When it comes to motors, you’ll want these with an acceptable KV. Typically, a variety of 1200KV to 1600KV suits effectively for 8S, akin to 1600-2100KV on 6S. You probably have 6S motors appropriate with an 8S voltage, they’ll nonetheless be utilized by utilizing a 75% output restrict in Betaflight, just like how folks fly 6S on 4S motors.
RCINPower 2207 1600KV is among the first motors designed particularly for 8S:
FC and ESC
Moreover, an 8S-compatible FC/ESC stack is a necessity. As of now, the choices are restricted, the one choice I’m conscious of is the Foxeer stack:
- 8S appropriate Flight Controller:
- 8S appropriate 4in1 ESC:
Benefits of Greater Voltages
Utilizing greater voltage to energy our FPV drones has many benefits, which explains why 6S is extra widespread than 4S these days for five″ FPV drones. I’ve beforehand defined the advantages of transitioning from 4S to 6S on this article: https://oscarliang.com/6s-mini-quad-racing-drone/.
The primary take away from the above article is that when delivering a certain quantity of energy, the next voltage can obtain this at a decrease present. This leads to much less heating in every single place – your battery, the XT60 connector, the wires, the ESC, and the motors. A lowered present additionally mitigates battery voltage sag, this in flip boosts throttle management and responsiveness and maintains constant efficiency all through the whole flight.
Switching from 6S to 8S carries many of those similar benefits, reminiscent of much less voltage sag, greater effectivity because of lowered system losses. Nonetheless, because the voltage continues to extend, the returns start to decrease. It’s essential, subsequently, to weigh these advantages in opposition to the potential drawbacks of upper voltage, as we’ll discover subsequent.
The Difficulty with Greater Voltages
As defined in my motor purchaser’s information, Motor KV represents the motor’s pace measured in RPM per volt utilized. In essence, to attain the identical RPM, you want decrease KV motors when utilizing greater cell depend batteries.
To make a decrease KV motor, we’d like extra turns of the wire across the stator, which might doubtlessly result in worse cooling efficiency. When switching to 8S, the rise in motor stator windings may not pose a major cooling problem in comparison with 6S, and more than likely to be offset by decrease present and effectivity acquire. Nonetheless, when contemplating even greater voltages reminiscent of 12S or 16S, cooling might grow to be a problem, which requires additional testing to confirm.
At current, 8S batteries are fairly uncommon, and if discovered, are usually far pricier than 6S batteries. Additionally they are usually bulkier, including weight to the drone and rising the probability of battery ejection and harm throughout a crash.
Moreover, only a few FPV drone elements (reminiscent of FC and VTX) can deal with the upper voltage of 8S. If incompatible, a voltage regulator could be wanted to energy your electronics. Most elements are designed with 6S in thoughts and will not have undergone sufficient testing for 8S compatibility, doubtlessly rising the chance of failure.
When utilizing 8S, it’s essential to watch voltage intently. As a consequence of efficiency not degrading as considerably as with decrease cell depend batteries even at low voltage, it’s straightforward to miss and overdischarge the battery, risking a sudden drone drop with out substantial warning.
Conclusion: Not Beneficial in 2023
It’s tempting to construct a 8S quad, however at this cut-off date, my private recommendation could be to carry off for a bit.
Firstly, it’s more likely to be a expensive venture. You have to to put money into new 8S batteries and appropriate chargers. The choices for motors and ESCs are restricted. Even when obtainable, sturdiness is usually a concern with 8S, given that almost all elements are solely examined for 6S, and complete testing for 8S is but to be performed.
Secondly, the potential for damaging an 8S LiPo battery is greater, given the bigger variety of cells.
In a nutshell, 8S might doubtlessly outshine 6S when it comes to flight efficiency when paired with the precise setup – on paper it ought to be extra responsive and highly effective. Nonetheless, it does current important challenges, reminiscent of greater prices and an absence of dependable {hardware} choices. Additionally, it may not go well with all flying kinds. Over time, as extra producers delve into the event and testing of 8S-compatible elements, it would grow to be a extra possible selection. As at all times, your private wants and flying type ought to be the guiding components when deciding whether or not to modify.
Edit Historical past
- Jul 2023 – article created
- Jan 2024 – up to date product hyperlinks
