LiPo batteries power the flight of your drone and are an important part of building your own fpv. The first thing you should be aware of is that LiPo batteries are not the same as other batteries you might be accustomed to. A LiPo battery will become forever damaged if it is overcharged or overdrained, and it may even catch fire. Before we start, we would like to make it clear that lipo batteries are not a fun item, they are dangerous.
How Safe Are LiPo Batteries?
LiPo batteries may be completely safe when used correctly. Lithium-ion batteries have a lot of potential ignition sources. Only when you handle them improperly or when they sustain bodily harm does that frequently occur. You should be fine if you handle your batteries gently and carefully.
How Do I Choose to Buy a LiPo?
Maybe you only want to know what battery to buy and don’t care to learn about LiPo. Here are a few batteries I’ve used and would suggest.
For RC Car
The most popular LiPo application is a 7.4V (2S) pack, which is the voltage that most closely mimics the voltages used in an old-style 6-cell NiMH pack. However, 11.1V (3S) or higher may be better if you are trying to achieve insane speeds or run a large electric vehicle.
For RC Airplane & Heli
The most popular choice among rc hobbyists is the lipo battery. they are powered by 3S or 4S lipo.So My first choice is 3S 2200mAh 11.1V 35C Lipo battery.
For FPV Drone
Different types of drones require different lithium battery sizes. If you use the wrong lithium battery specifications, you will either have weak power or burn out the drone’s motor with flight controls and ESCs.
| Battery Cells | Volts | mAh | Discharge Rate | Connector | |
|---|---|---|---|---|---|
| 2'' FPV Drone | 2S | 7.4V | 300-650mAh | 45c-60c | XT30 |
| 3'' FPV Drone | 3S | 11.1V | 300-650mAh | 45c-80c | XT30 |
4S Lipo batteries and 6S LiPo batteries for a 5′′ FPV drone.
You can see most pilots use 4S batteries 850-1800mAh for 5″ freestyle drones.
Most pilots use 6S battery 1300mAh for 5″ racing drones with high C-rating.
To understand more about using LiPo, I do advise thoroughly reading this post. Bad habits can drastically reduce the life of your battery or, in rare circumstances, even cause a fatal LiPo fire.
Calculate the drone power needs
You should be able to obtain thrust statistics for your motor and what current it will draw for the propeller sizes that it supports once you have chosen on the motor and propeller size. For instance, this motor with 5146×3 propellers may draw up to 41.67A at full throttle.
| Motor | Volts | Props | Throttle | Amps | Watts | Thrust | RPM | Efficiency | Temperature |
|---|---|---|---|---|---|---|---|---|---|
| MCK V3.0 | 24v | 5146x3 | 50% | 7.91 | 195.3 | 657.19 | 19367.09 | 3.46 | 91% |
| 100% | 41.67 | 982.8 | 1764.67 | 31606.58 | 1.82 |
At full power, a quad motor configuration would draw a maximum total current of 41.67 x 4 = 166.68A. Just use this number to find a battery with a high enough C rating if you want to be safe. However, since we rarely fly at full throttle for more than a few seconds (my personal preference is to fly at about 40-60% throttle), I often reduce it by 30-40%. Second, because of the flowing air in real life, as opposed to static thrust testing, motors draw far less current.
Other components would also draw current, but they would do so insignificantly compared to the motors, so you can usually overlook them.
Can I use a 4S LiPo battery in a racing drone? or 6S LiPo battery in a freestyle drone?
It depends on the track for racing. 6S would be great for endurance racing since it allows for longer flying times without the pilot noticeably sensing the weight. The situation where 6S wouldn’t make a significant difference is on narrow courses.
The improvement on a freestyle setup primarily depends on your flying technique. A 4S battery could be optimal for smooth, leisurely flight. however, a throttle-limited 6S might also work. 6S could be the best option for really acrobatic freestyle flying. The most significant piece of advice I can provide is to give the 6S a go and see how you like it.
What is a Lithium Battery?
Lithium polymer (AKA “LiPo”) batteries, use lithium ion technology instead of the liquid electrolyte normally used. These batteries are rechargeable, thus providing significant cost savings to the user.
Why Does FPV Use Li-Po’s And Not Li-ions?
Limited by power delivery and size, Li-ion batteries do not have a high discharge capacity, even the 21700 4200mAh Li-ion pack has only 45 amps discharge capacity. Not only are they large in size, they also weigh 400g. This is very heavy for a 5″ fpv drone.
In fact, lithium polymer (LiPo) batteries are often used to power FPVs due to their high energy density, high c-rate, and light weight.
LiPo is the default configuration for most battery-powered RC cars and planes.
LiHV Battery
An other form of lithium-ion polymer battery is called a LiHv battery, where “Hv” stands for “high voltage.” In comparison to conventional LiPo batteries, it consumes more energy. While a typical lithium polymer battery’s peak cell voltage is 4.2V and its nominal voltage is just 3.65 to 3.7V, a LiHv battery may charge to 4.35V or higher per cell.
You may ask: Can I charge normal LiPo batteries to 4.35V? The maximum charge voltage for normal LiPo batteries is 4.2V per cell. Anything higher will overcharge the battery and is not recommended.
Storage Voltage
A new lipo battery will already be half charged when you purchase it. The Storage Voltage is the name given to this incomplete charge. Each cell is charged to a storage voltage of around 3.8 volts. A lipo battery is most stable at that voltage, that explains reasons. The battery will gradually degrade and lose efficiency if the cell has any extra or less energy. This is another reason why it’s crucial to quickly recharge or drain your batteries to storage voltage after using them.
What Do The Parameters of The LiPo Battery Mean?
LiPo Cell Voltage
Standard lipo battery cells have an useful voltage range of 3.2 to 4.2 volts. The battery may sustain long-term harm if the voltage is lower than 3.2v. Any voltage above 4.2v greatly increases the likelihood of a battery catching fire. Typically, you’ll start with a battery cell that is at storage charge or 3.8 volts, put it on the charger, let the charger charge it to 4.2 volts, and then let it fly until the voltage drops to somewhere between 3.5 volts and 3.7 volts, depending on your comfort level or how sweet you need to be to your battery cells.
You may ask why I can’t fly to 3.2 volts, it is also in the safe voltage range.Flying to 3.2 volts puts extra stress on the batteries, shortening their life, and you may want to have a burst of throttle to make a perfect finish while you are about to reach 3.2 volts.At this point the battery will sag, the voltage will drop, and going below 3.2 volts will cause more damage to the battery.
Battery Cells
LiPO battery packs are generally sold in types of 1S, 2S, 3S, 4S, 5S, or 6S, where the number after the “S” denotes the number of cells in that specific pack. The voltage of the entire pack increases with the number of cells.
- 1S = 1 cell = 3.7V
- 2S = 2 cells = 7.4V
- 3S = 3 cells = 11.1V
- 4S = 4 cells = 14.8V
- 5S = 5 cells = 18.5V
- 6S = 6 cells = 22.2V
A battery might also be stated as 4s2p or 4s1p. In order to get the appropriate voltage and capacity for the full battery, some batteries are connected in series with others in parallel. This only informs the pilot of this.
A 6s battery may be charged to a maximum of 25.2 volts. The electric motor will spin more quickly the greater the voltage. For this reason, it’s crucial to match the proper motor speed with the proper battery voltage.
Battery Capacity
The amount of current a batteries can provide per unit of time is expressed in milliamp hours (mAh), which is the unit used to measure battery capacity.
As an illustration, a 900 mAh battery is capable of providing 900 mAh (0.9A) of electricity for an hour. A battery with a greater mAh rating may, in theory, fly for longer between charges. Battery size and weight must be traded off when selecting a battery. Longer flying times will be possible with a bigger battery, but the quadcopter’s performance will be constrained by the extra weight.
In fact when you purchasing fpv accessories, the manufacturer will tell you the recommended battery capacity and other specifications.
Battery C-Rating
The amount of current that a battery can sustainably deliver for a specific charging process is measured by its C-Rating. Simply explained, a battery’s C-Rating indicates how much continuous current it can produce. The theoretical maximum discharge current of the pack may be calculated by multiplying the C-Rating by the battery’s capacity.
A battery with a C-Rating of 70C or greater is often advised for most 220 size quadcopters.
Here is the conversion formula.
C-Rating Formula: Maximum Safe Current Draw (mA) = Battery Capacity (mAh) * C-Rating
Milliamp Hour Conversion Formula: 1000mA=1A (one amp is one thousand milliamps)
Calculating the compatibility of various motors, propellers, electronic speed controllers (ESCs), and batteries is another application of the C-Rating method. A 1500mAh 100C battery has a safe continuous current of 150A(150,000mA). The maximum continuous current(37.5A) that this battery can deliver to each motor is made evident by dividing this amount by 4 (because the quadcopter has four motors).
The ESC may then be chosen appropriately to handle the highest constant power (in this case, a 35-40A ESC would be the most appropriate). The majority of batteries may often safely momentarily surpass their rated constant current for up to 10 seconds.This says that if the average motor current is less than the predicted maximum continuous current for each motor, the motor-props combo can be used with a battery.
There is also a useful data resource here as it provides comparative data on maximum current draw and thrust for many different motor and propeller combinations.
Internal Resistance
All electrical parts have resistors, even a piece of wire, including a battery. The internal resistance (IR) is the resistance in a battery.
IR can be used to measure a LiPo battery’s health, it’s a useful indicator to decide whether to replace your LiPo battery. Lower IR means that the battery can work more efficiently to power your FPV drone, which means less wasted power.
It is inevitable and irreversible that the IR in LiPo cells will slowly increase with time and use. These mistakes will age your LiPo faster:
Overdischarge and overcharge
Overcharging the battery by discharging at a current higher than it’s rated for a prolonged period.
Overheating
The internal resistance of the cells is the biggest factor that affects the maximum discharge rate of a battery. If your battery has a high internal resistance, the voltage of the battery will drop more significantly as you increase the throttle – a common problem known as “voltage sag”. As the voltage drops, the motor loses speed, ultimately reducing the drone’s responsiveness.
Some batteries are designed for low current applications (e.g. an 8C or 10C rated battery designed to power a radio), the IR is going to be higher by nature. You shouldn’t be concerned because the IR of 18650 Li-ion batteries is significantly greater than that of regular LiPo batteries.
Battery Connectors
There are several LiPO battery connections available. The yellow XT60 connection, which is used on about 95% of 220mm-sized quadcopters powered by 3S-6S LiPO FPV Drone Batteries, is the most widely utilized connector. The JST-XH is frequently used in micro drones like the Tiny Whoop because it offers more current flow from the battery than the JST-PH, which is smaller. The most popular battery connections are shown in the images below:
Balance Connectors
LiPO batteries will also feature a balancing lead, excepting 1S cells. To balance charge the battery pack, a typical JST-XH connection with 3–7 pins is used.
When charging, the balance lead must be connected to the charger. This enables the charger to monitor and balance the voltage of each cell as it charges. Important: Before charging, always plug in the balancing lead!
For a 2S LiPo, the number of wires in a balancing lead starts at 3, and increases by 1 with each additional cell count:
- 2S – 3 wires
- 3S – 4 wires
- 4S – 5 wires
- 5S – 6 wires
- 6S – 7 wires
It’s worth noting: It’s common for balance wires to be damaged by a spinning propeller during flight.
How Do I Charge The Lipo Battery & Correct Way to Charge?
1.You Need Get A LiPo Charging
Because of the strict charging specifications for Lithium Polymer batteries, you’ll need a charger designed exclusively for LiPo batteries.
2.Connect LiPo Batteries To A Charging Device
Charging LiPo batteries with most modern LiPo chargers could not be easier. All you need to do is plug in the XT60 and Balance connectors, configure a few settings, and you are ready to go.
3.Switching Charger Modes
Balance Charge
As the battery is charged, the charger monitors the voltage of each cell to maintain balance. This is the safest and most recommended method of charging your LiPo battery. Why need charge a balance? Each battery cell varies just a little. You can discover that the cell voltages are all different after the trip. Without connecting the balancing connection, it is likely that some cells may charge to below 4.2 volts while others would charge to above 4.2 volts, which is hazardous.
Balance charging is the default and sole charging mode on the majority of contemporary LiPo chargers. Get a good charger right immediately if your outdated or inexpensive charger allows you to charge without a balance lead.
Storage Charge
The charger raises the voltage of each cell to its storage level (which is 3.80V – 3.85V, depending on the charger).
Quick Charge
Because it doesn’t track and balance the voltage of the individual cells, charging occurs more quickly in this mode. There is a chance of overcharging one or more cells because it only considers the overall voltage of the entire pack. If you don’t have any prior experience, I strongly advise against using this method.
Discharge
The charger tries to discharge the Lipo battery (it can be extremely slow depends on the discharging power of the charger)
Trickle Charge
The voltage will naturally drop if the batteries are left unused for a long time, or if they are used too long after a flight and not recharged in time. The charger loses the ability to recognize the cell or the entire battery when the cell voltage drops too low. The “trickle charge mode” into play at this point; gradually pushing current into the battery to revive the dead cells. Note that “battery resurrection” depends on the condition of the cell; some batteries may be too damaged for this to work.
Correct Way To Charge
You need to understand a few things about charging if you want to extend the usable life of your battery as much as possible. It’s important to charge your batteries away from materials and anything that could catch fire. Never leave batteries that are charging unattended. The likelihood of a fire is significantly enhanced when a lipo is charging. To increase your chances of quickly removing the battery in the event of a fire, try to charge indoors near a window or door.
A battery that has been excessively discharged or damaged in an accident might be extremely dangerous, but a healthy unbroken lipo that is charged correctly is unlikely to catch fire.
As said above, I recommend buying a charger with a built-in balancing function because it balances the behavior of the voltage of each cell in the battery pack, which helps improve the performance of the battery. Then your battery is to charge at a rate of “1C” or 1X capacity.
A charge rate of 1C means that the current will fill the entire battery in 1 hour. If you have a 1300mAh battery charging at 1C, you would set the charger to 1.3 amps.
Here are other safety rules
- LiPo batteries may catch fire if handled incorrectly. Before handling or charging batteries, take the time to review these safety precautions.
- LiPo batteries should be handled by the case, not by the wires, which can come loose from the delicate solder connections.
- After using your battery, wait until it has cooled down completely before recharging it.
- Never use or charge a damaged or swollen battery.
- Before charging, verify that the charger’s settings are correct for the battery type and number of cells.
- Although the charger usually prevents overcharging, it is a good idea to check the voltage of the cells frequently.
- Never expose a battery to direct sunlight.
- Before charging a battery, always remove it from the device it powers and place it in a safe location.
- Never, never, never short a battery’s terminals.
How To Charge Multiple Lipo Batteries At The Same Time？
Although it may not be the safest way to charge a LiPo battery, parallel charging is a fast way to charge multiple batteries at once.
What Should I Pay For A Charger?
A LiPo charger will probably last for years, much like your radio transmitter and FPV goggles, making it one of the biggest long-term investments in the RC hobby. So instead of skimping on quality, I would advise you to invest a little more.
The most expensive charger may not always be the best, but a great quality charger can be purchased for a fair price. My recommendation is to determine what you really need before looking at the cost. Find the chargers that meet your needs by writing them down on a piece of paper. Do not include the “fancy features” if you do not need them.
How To Protect And Store The Batteries?
It is better to use a lipo battery “soon” after it has been charged and to put it back into storage after usage. This is due to the fact that a battery that is not at storage voltage continuously deteriorates over time and sustains cumulative harm. When used, a battery that has been fully charged for a month, for instance, may have a significantly increased internal resistance, which will result in decreased performance and greater heat. How long to leave a lipo completely charged has no set duration.
The equivalent of leaving it completely charged for 10 days straight is leaving it fully charged for one day 10 different times.Therefore, it would be better to put batteries set up storage voltage if you find yourself with some fully charged batteries and no quick plan to use them.LiPo Battery should be stored at room temperature at 3.8V per cell.
Both heat and cold are the enemies of lipo batteries. Please do not let lipo batteries get very hot during use and charging.And low temperatures can reduce the performance of Lipo batteries. Try to keep your battery warm, but not too hot, before using it in cold weather.
They should also be stored in a fireproof case of some sort.You can put the batteries into LiPo bags or explosion-proof boxes, and they can protect your room from catching fire once the LiPo is burning.
Again: It’s very likely that you’ll need to buy new LiPo batteries sooner than you think if you store them in a “laissez-faire” way.
How To Dispose of Bad Batteries?
Given that they provide a fire hazard, nobody really wants to keep them around.Most lipo batteries lose a lot of performance after 300 or more charge cycles, at which point it’s best to retire them.In the safe case, try to discharge the lipo battery, and then check whether the voltage of the lipo battery is 0.0 V. Finally, the battery will be thrown into the garbage can dedicated to battery storage.
Conclusion
You now know the majority of what you need to know about LiPo batteries, so there you have it. It gives you some knowledge of how they work.
Battery FAQ
Here is a collection of frequently asked questions from hobbyists.
Are puffed-up (swollen) LiPo batteries harmful?
Yes, it’s dangerous to use or store LiPo batteries that have swelled.
What results in the swelling of LiPo batteries?
LiPo expands as a result of trapped gas inside the cells. Physical abuse (such as breakage, overheating, or over-discharging) might cause the battery to produce additional gas, which is a normal occurrence.
Can puffed LiPo be fixed?
Not at all. Once LiPo has enlarged, the damage is permanent. As soon as you can, properly dispose of it.
