It may be difficult for you to choose between 4S battery and 6S liPo battery if you are new to flying FPV drones. I’ll go over the distinctions in this piece to assist you in making a wise choice. Additionally, when we fast-forward to 2023, the talk is now about an even higher voltage, 8S battery.
Difference between 4s battery and 6s battery?
The voltage is the main distinction between the 4S and 6S LiPo batteries. Four 3.7V cells connected in series make up the 4S pack, which has a nominal voltage of about 14.8 volts. Six cells are linked in series to create the 6S pack, which has a nominal voltage of roughly 22.2 volts. When compared to the 4S battery, the 6S battery’s higher voltage allows it to give more power and better performance. However, it may lose power more quickly, which results in shorter flight periods.
1 Power and Batteries
- P = I x V
- P = Power (watts/W)
- I = Current (amps/A)
- V = Voltage (volts/V)
An object’s power is a measurement of its work capacity. Racing quads can consume about 2,500 watts (2.5 kilowatts/kW) of power when operating at maximum speed. That is the equivalent of 3% of a Honda Fit’s power (the VTEC variant, that is)!
The problem with a 4S lipo is that it needs to have a high current capacity in order to give the craft that much power. Based on the 2.5kW power consumption case, a 4S battery would need to deliver approximately 169A of current (2.5kW/14.8V = ~169A) to maintain the drone’s trajectory. This amount of power and current can be supplied by high-end and/or big capacity 4S packs, but prolonged high current consumption can harm the battery cells, significantly reducing pack longevity.
The benefit of a 6S pack is that the voltage rise drastically lowers the current needed to give the craft the same amount of power. Using the given scenario, the 6S battery would only need to deliver ~112A of current (2.5kW/22.2V=~112A) in order to power the craft for 2.5kW.
The lifespan of a battery pack can be extended by lowering its current demand. This is so that there is less stress on the pack as a whole as each cell just needs to draw a smaller amount of current. The individual cells of a battery pack are connected in series, or like a chain. Each cell in the pack must produce 50A of current when the battery is required to supply a current load of, say, 50A. Each cell in a 6S pack does not need to produce as much current as the cells in a 4S battery because there are more cells in a 6S pack. This is presuming that the same amount of power must be supplied by both packs.
The current draw of the 6S pack will increase if a 6S fpv drone’s power consumption is higher than that of a 4S drone, for example, because of larger or higher kV motors. This will cause just as much harm as taking a high current from a 4S battery. If the weight of the two craft is comparable, the 6S craft can outperform the 4S fpv drone with larger, faster motors; nonetheless, for most racing situations, the 4S racing drone’s present speed and acceleration are more than sufficient.
Battery Capacity and Weight
One apparent drawback of 6S packs is that a battery with the same capacity as a 4S can weigh about 50% more. While this is true, a 6S drone racing battery can have a capacity that is sufficiently less than that of a 4S battery while yet providing the same amount of power for a predetermined amount of time.
19.2 Wh of energy translates to 19.2 watts for one hour, 38.4 watts for thirty minutes, or 1185 watts for sixty seconds from the batteries. The energy storage capacity of both batteries is equal, as demonstrated by the above equation. This basically means that a quad with either battery could fly for about the same amount of time. This is predicated on the idea that the two quad copters weigh roughly the same and use the same amount of power.
Utilizing a 6S battery pack with a lower capacity has the drawback of lowering the cells’ current drawing capacity due to their reduced surface area. Because of this, a lot of 6S drone racing setups will use batteries with a capacity of about 1000mAh.
Motor kV
4S or 6S batteries power 5 inch FPV drones. The KV ratings of your motor must guide your battery selection. For instance, the CNHL 4S 2000mAh and CNHL 6S 1500mAh are great choices for 2000–3000KV and 1600–1900kV, respectively. Lower KV alternatives are more economical and cautious, whereas higher KV options are typically more aggressive and power-hungry. A LiPo battery’s capacity, expressed in milliampere-hours (mAh), tells you how much current you can continually drain from the pack for an hour, or until it runs out. Because larger batteries have a greater take-off weight, they can significantly impair flight performance. The space that large LIPO packs require on top of your drones is another drawback to using them.
Choose 4s battery or 6s battery for your racing drone?
Theoretically, a high kV 4S rig (2600kV and higher) can’t match the torque and top speed of a 6S FPV drone with low KV (1600-2000kV) motors. Here I will introduce the benefits of 6S Over 4S.
amp draw
One of 6S’s most significant advantages over 4S is that less current is needed to provide the same amount of power. Voltage multiplies current equals power, or P = V x I. Increased voltage will result in decreased current to produce the same amount of power. For instance, it requires almost 60A on 4S (at 16.8V) to produce 1000W, but only slightly less than 40A on 6S (at 25.2V).
Reduced amp draw means:
- Reduced strain on your battery
- Reduced “voltage sag” throughout the flight
- Less losses from resistance in the cables are also there, but they are minimal.
responsiveness and performance
The motors can change RPM more quickly and consistently and accelerate more consistently under load because to the reduced voltage sag. This makes the aircraft more responsive and nimble overall. One of the most important things about how your quad handles is likely the faster rate of RPM change.
Can you Use 4S battery on 6S fpv Drone?
Before attempting this, confirm that your hardware supports 6S voltage! If not, you risk burning your FC and ESC.
You cannot increase the motor output of a 6S quad to 150% and expect it to function similarly on a 4S LiPo. Motor output cannot be increased; it can only be decreased. In Betaflight, reducing motor output essentially limits the output of the ESC, specifically the signal duty cycle to the FETs (the duration of high pulses).
When will you need to fly 8s battery?
It is necessary for you to use motors with the proper KV. For 8S, a range of 1200–1500 KV works well, which is similar to 1600–2000 KV for 6S. Similar to how 6S motors be flown on 4S motors, 6S motors that are compatible with an 8S voltage can still be flown in Betaflight with a 75% power limit. It also requires an FC/ESC stack that is 8S compliant.
Advantages of 8s lipo battery
The primary lesson to be learned from the aforementioned essay is that a greater voltage can accomplish a given quantity of power delivery at a lower current. As a result, your battery, the XT60 connector, the wires, the ESC, and the motors all get less heated. Lower current also lessens battery voltage sag, which improves throttle response and control and keeps the aircraft operating at a steady state of performance for the duration of the flight.
Many of the benefits of switching from 6S to 8S remain the same, including lower voltage sag and increased efficiency from fewer system losses. But the returns start to decrease as the voltage keeps rising. Therefore, as we’ll discuss next, it’s critical to balance these advantages against any potential disadvantages of higher voltage.
Do you recommend 8s lipo battery?
Not Recommended in 2023. Although building an 8S drone is enticing, I would personally advise delaying for the time being. First of all, the endeavor will probably be expensive. Purchases of brand-new 8S batteries and appropriate chargers are required. There is a limited selection of motors and ESCs. Durability can be an issue with 8S even when it is accessible, since most components are only tested for 6S and extensive testing for 8S has not yet been done.
Second, because an 8S LiPo battery has more cells, there is a greater chance of damage.
In summary, with the correct configuration, 8S should be able to outperform 6S in terms of flight performance because it is, theoretically, more powerful and responsive. It does, however, come with some serious drawbacks, including greater prices and a dearth of dependable hardware solutions. It might not fit every flying style, too. It may become a more viable option if more manufacturers work on creating and testing 8S-compatible components over time. As usual, the decision to swap should be based on your own demands and flying style.