Disclaimer: All information on this page should be considered general advice/opinion. You are solely responsible for ensuring the safe operation of the battery. Further use of the information on this page will be at your own risk.
FPV Drones/Racing Drones are powered by Lithium Polymer (short for LiPo, Li-Po, Li-Pol or Li-polymer) rechargeable batteries, which are capable of storing and delivering large amounts of energy. In this guide, you will learn about marking/tech. LiPo specifications, as well as how to select, safely operate and dispose of batteries.
Is a LiPo battery a safe power source?
There are many reasons why LiPo batteries can catch fire. As a rule, this happens only when their operation is not carried out properly, as a result of their physical damage, or due to marriage. If you buy batteries from trusted brands and use them carefully, then everything will be in order. However, we recommend that you carefully read the material in the manual to learn how to properly handle lithium polymer batteries. Remember, safety is above all!
Basic information about LiPo batteries for mini drones
Lithium polymer batteries, better known as LiPo, have a high energy storage density, high discharge rate, and light weight, making them an excellent candidate for powering RC models. Having familiarized yourself with the basics of LiPo batteries, you can easily read and, most importantly, understand their specification.
Battery voltage and number of cells (S)
LiPo batteries are made up of individual cells/cells/cell(s) (also referred to as “S”; they are referred to as “cans” in the hobby). Each LiPo cell/jar has a nominal voltage of 3.7V. If a higher voltage is required, these cells can be connected in series to subsequently form a single battery.
Usually, when referring to a lithium-polymer battery, they do not refer to the battery voltage, but to the number of cells (cans) in the battery or to the number of “S”:
- 1S = 1 cell (1-cell battery) = 3.7V
- 2S = 2 cells (2 cell battery) = 7.4V
- 3S = 3 cells (3-cell battery) = 11.1V
- 4S = 4 cells (4-cell battery) = 14.8V
- 5S = 5 cells (5 cell battery) = 18.5V
- 6S = 6 cells (6 cell battery) = 22.2V
For example: A 14.8V battery is called a “4-cell” or “4S” battery.
- Voltage directly affects the speed of brushless motors, so if the motors/ESCs and other electronic components used on your drone support higher voltages, then you can use batteries with a higher number of cells to significantly increase the speed potential of your quad.
- It should be understood that a battery with a large number of cans with the same capacity becomes heavier, since it contains more elements that make up the battery, and excess weight, as we already know, negatively affects the flight characteristics of the drone.
- To make a 4S 1000mAh battery and save some weight, you can simply daisy chain two 2S 1000mAh or one 3S 1000mAh with a 1S 1000mAh battery.
- The nominal voltage of LiPo batteries is 3.7V. This value has nothing to do with the voltage that the battery can produce when fully charged or discharged. The nominal voltage is set by the manufacturers of these batteries and is the optimal and safe value for each individual battery.
- The LiPo battery is designed to operate within the safe voltage range of 3 to 4.2V per cell. Discharging below 3V can result in permanent loss of performance and even damage to the battery. Overcharging above 4.2V can be dangerous and eventually cause a fire. Despite this, it is recommended to stop the battery when its voltage reaches 3.5V. For example, for 3S Lipo, the maximum voltage is 12.6V and you should land the drone when the voltage reaches 10.5V (i.e. at 3.5V per can).
Capacity and size of LiPo battery
The capacity of a LiPo battery is measured in mAh/mAh (milli-amp hours). “mAh” is essentially a measure of how much current you can draw from a battery for an hour before it runs out.
For example: For a 2000 mAh Lipo battery, it will take an hour to fully discharge if you discharge it continuously at 2A. If the current consumption is doubled to 4A, the duration will be halved (2/4 = 0.5). If you increase the current consumption to 40A in non-stop mode, then it will take only 3 minutes to fully discharge such a battery (2/40 \u003d 1/20 hour).
- Increasing the capacity of the battery leads to an increase in flight time, but with an increase in capacity, the weight and physical dimensions of the battery also increase. In this case, it is necessary to find a compromise between power and weight, which in turn affect the flight time and maneuverability of the drone. Among other things, a higher capacity predetermines a higher discharge current, which we will discuss in the next section.
Just in case, we recall that 1000 mAh = 1Ah.
C-rating (discharge rate)
Lithium-polymer batteries designed to power drones have in their specification such an important parameter as C-rating/Current output/Discharge rate (English C-Rating/Discharge Rate). Knowing the nominal value of “C” and the capacity of the battery, we can calculate the theoretical safe continuous maximum discharge current of a LiPo battery: Max. Discharge Current = C-Rating × Capacity/1000.
For example: A battery with specifications: 2000 mAh 65C has a rated max. continuous discharge current (continuous max discharge current) – 130A.
Continuous and Peak
Also, two “C-Rating” values \u200b\u200bcan be displayed on a lithium-polymer battery at once: “Continuous” and “Peak (Burst)”. The value of the peak rating (usually twice the continuous rating) indicates the max. the current that the battery can deliver in a short period of time (usually about 10 seconds).
- Despite the fact that this parameter is one of the priority characteristics of the battery, it has now become the main marketing tool, and often the values indicated on the battery are far from the real values in practice. In this connection, it is recommended to buy batteries only from manufacturers recommended in the hobby!
- Too low a C-rating value will not allow the drone to develop its maximum flight potential and it will be less dynamic. And if the current exceeds the nominal value, then you can even damage the battery as a result.
- When the C-rating is higher than required, you won’t get much improvement in performance. Instead, the battery will be heavier, again negatively impacting flight time.
C-rating charge (Charge Rate)
C-rating charge / charge rate (eng. Charge Rate) is another equally important parameter that can be displayed on the battery. Often, most rechargeable batteries are designed for a charge rate of 1C. This value determines the maximum allowable current that can safely charge the battery. Calculate max. the possible charging current for a particular battery can be given by the formula: Capacity (mAh) / 1000 × “Charge Rate” = XX amps. The charge current value is one of several preset settings for the charger before charging the battery.
For example: If you have a LiPo battery with a capacity of 2200 mAh with a charge rating of 2C, then the maximum allowable charging current for it is 4.4A.
If you do not see the “Charge Rate” value on the front side of the battery, then it is probably mentioned on its back side.
- Exceeding max. allowable value of the charge current will inevitably lead to battery fire!
- The lower the current you charge, the longer the LiPo battery will take to charge.
- Slow charging prolongs battery life. If you have time, take your time.
- If the “Charge Rate” value is missing, do not take risks and charge with a 1C rating.
Main battery connectors
Rule of thumb or rule of thumb: The battery connector must match the one used on the drone. If you’re building a drone from scratch, then choose the one that works best for you and stick with it throughout your development in the hobby. This approach will allow you to easily change batteries, and if you decide to build another drone in the future, you can use the same batteries.
All Lipo batteries have in their arsenal two outgoing sets of wires with different types of connectors / connectors at the ends of each: Balance wire and Main or discharge (with the exception of 1S batteries, which have only a main wire). The range of connectors used on LiPo batteries is quite wide. The main differences are the shape, weight and allowable current.
Connectors for 1S battery
1S battery connectors are tiny and therefore designed for a small current rating. Batteries with this connector are usually used to power micro quads, as well as for toy copters built on brushed motors.
Connectors for 2S-6S batteries
For this category of batteries, you will find many more different types of connectors. In the list below, not all are listed, since most of the missing ones are not used so often in the hobby, and you should not bother with them. For mini quads, the XT60 connector has been and remains the most popular. But since the allowable current for this connector is no more than 60A, and the power potential of such drones is constantly growing, it will be replaced by other more powerful connectors in the near future.
- JST (mainly equipped with 2S batteries)
- XT30 (mainly equipped with 2S and 3S batteries)
- XT60 (mainly equipped with 3S and 4S batteries)
- XT90 (mainly equipped with 4S and 6S batteries)
- EC5 (one to one like the one above, just bigger)
- Deans (T)
The balancing connector is mainly used for balanced charging of the battery. Such charging guarantees a uniform charge of each battery bank. The number of wires for a balanced output depends on the number of battery cells, three wires have a 2S battery, four wires have a 3S battery, and so on.
LiHV (also known as: LiPoHV / High Voltage Li-Po / LiPo HV) is a type of conventional lithium polymer battery, where the abbreviation HV stands for “High Voltage or High Voltage”. Compared to conventional LiPo batteries, LiHV batteries have an increased energy capacity and can be safely charged up to 4.35V per cell.
In the list of advantages of LiHV batteries:
- Smaller and lighter for the same capacity
- Provide more dynamic RC model
- Longer run time
- Less voltage drop at maximum operating modes
- It is believed that against the background of increased performance, LiHV batteries have a shorter service life.
- In practice, it has been found that compared to conventional LiPo, LiHV batteries do not provide a noticeable increase in flight duration. However, things change when it comes to choosing power for FPV goggles/helmets/control gear. Here, the advantage of LiHV in the duration of work is obvious and undeniable.
- To charge LiHV, it is recommended to use chargers that support the charging of such batteries.
- It is not recommended to charge LiPo batteries together with LiHV batteries, as this can also cause a fire in regular LiPos.
- It is strictly forbidden to charge ordinary LiPos to a voltage of 4.30V-4.35V in the hope of increasing their performance! Otherwise, it will lead to battery fire!
Internal resistance (IR – Internal Resistance) determines the quality of a LiPo battery. The lower the value, the better. Higher internal resistance reduces the maximum current the LiPo can draw and increases the voltage drop. As a result, most of the energy is wasted and released as heat, which ultimately contributes to overheating of the battery.
- The internal resistance of a LiPo battery increases during operation, and the process itself is inevitable and irreversible. That is why, over time, batteries cease to give out their former potential, which in turn affects the dynamism of the drone’s flight.
- The IR value will be different for each individual cell of LiPo battery. The highest value will limit its effectiveness.
- A large spread between the values of each jar indicates its poor condition, and the smallest one indicates a good one.
- You can measure the internal resistance both using special user tools – testers (for example: YR1035), and using some chargers that have the function of measuring internal resistance (for example: ISDT Q6 Pro / Plus).
How to choose the right LiPo battery for a quad?
If you are choosing a battery for a production quad model, then everything is simple. It is enough to look into the specification of the drone and clarify the recommended battery parameters, through which to select a battery in the catalog of one of the well-known and trusted battery developers in the hobby, which we will talk about a little later. If the power supply is selected for a quadrocopter assembled from scratch, then in this case the selection path will be a little longer. The first step is to determine the basic power requirements of your build.
Max. current consumption
Since battery selection is often the last step in building your own drone, we already know which motors, ESCs, and props will be used in the build. By looking at the characteristics of the motors, in particular the thrust data table (usually provided by the motor manufacturer along with the specification), you can see how much current the motor consumes at max. thrust (at 100% throttle).
For example: The propeller assembly group consists of: 4 × iFlight XING-E 2207 1700KV motors; with 6045 propellers. If we look at the thrust table provided by the motor developer (see specification below), we can see that the current consumption for the selected motor with a 6-inch prop at max. thrust is 32.42A. Knowing the value of the current consumed by one motor, we determine the max. current consumption for quadcopter: 32.42A × 4 = 129.68A. In general, this figure can be used to select the optimal battery, but advanced users, due to the considerations noted below, reduce it by 10% i.e. 129.68 × 0.9 = 116.7A.
- It should be understood that due to the movement of air masses that occur in real flight, the value of the consumed current, as a rule, is always lower than the value obtained during the “static thrust tests”.
- The current at 90% gas and at 100% are cardinally different values. In practice, the operating range of the throttle stick is in the range of 40-80%, and the position of 90-100% is fixed for only a few seconds. From here the question is – how often will you fly in the “gas to the floor” mode?
- In addition to the motors, power consumption is carried out by other integral components of the drone, such as the flight controller (FC), receiver (RX), LED indication / backlight, FPV, and so on. However, compared to motors, the voltage consumption of these components is extremely small, so advanced users simply ignore them in the calculations, or, on the contrary, add 1-2A if they allow retrofitting the drone with energy-intensive components in the future.
Choosing the optimal battery capacity
It is known that the size of the propeller determines the size of the drone frame used. And knowing the size of the drone and the required C-rating, you can determine the optimal battery capacity. Since most advanced users refer to the size of the drone by the size of the propeller, in the process of advancing in the hobby, the so-called selection pattern was developed based on the diameter of the propellers used:
- For a quad on 6-inch props: 1500 mAh – 2200 mAh
- Quad 5″ prop: 1300 mAh – 1800 mAh
- For quad on 4-inch props: 850 mAh – 1300 mAh
- For a quad on 3-inch props: 650 mAh – 1000 mAh
For example: Let’s say you’re building a 6″ mini quad and your goal is to make it as easy to build as possible. In this case, it would be better to choose a battery with a capacity of 1500 mAh (1.5Ah).
With all these data, you can calculate the value of the peak discharge current (C-Rating Burst) using the formula: C-Rating Burst = Max. current consumption/capacity. Returning to our example, we get: 116.7A/1.5Ah ≈ 78C. As a rule, the value of “C Rating Continuous” is half the value of “C-Rating Burst”, respectively: 78/2 = 39C.
- If you are building a drone for high-speed flights (operating throttle range over 50%), then it will be better to choose batteries with a higher C-rating than the calculated one.
- Before choosing a battery based on the results of the calculation, decide on the future style of piloting. Think about what will be your priority – dynamism or flight time. For example, for an athlete participating in drone racing, flight speed / dynamism is important, so they prefer the lightest possible batteries, the capacity of which will be enough for exactly one race. Freestylers, on the other hand, are less focused on dynamics, which allows them to use higher capacity batteries, thereby extending the overall flight time.
Which brand to choose?
- Avoid “no-name” batteries and stick to popular brands in the hobby.
- You should not buy batteries from new brands, at least until the first stable positive reviews. It is also not uncommon for some new brands to really offer good batteries for the first time, and after the products are recognized in the hobby, they begin to reduce the quality in order to max. attraction of profit.
- The list of well-known and time-tested brands today includes: Tattu, Turnigy, Infinity, Dinogy, Luminier, GNB, URUAV, Acehe, XF Power, CNHL Ministar, RDQ series (if you are sure that this list is missing some brand let us know in the comments).
Choice of charger
Today there are many different chargers on the market and therefore, as in the case of choosing a battery, the best and most reliable solutions are offered only by time-tested brands, such as: ProLead RC, SKYRC, EV-PEAK, Tenergy, ToolkitRC, HOBBYMATE, ISDT (if you are sure that this list is missing a brand, let us know in the comments).
The batteries listed in the list have positively proven themselves in the hobby, but these are far from all the models that could be recommended.
The bundle of chargers does not always include all the necessary adapters for charging the battery, but this is not a problem, since you can always buy them. We have ranked all models in order from simple to advanced (if you are sure that something is missing from this list, let us know in the comments).
- SKYRC B6 AC V2
- SKYRC IMAX B6 mini
- ProLead RC B6 80AC
- Tenergy TB6AC+80W
- SKYRC Q200
- EV-PEAK C1-XR
- ToolkitRC M8
- HOBBYMATE D6 DUO PRO
- ISDT D2 Dual
- ISDT Q6 Pro
- ISDT 608AC
- ISDT T8
The battery charging process for all devices is almost identical. To learn how it all happens, we recommend watching this video.
The main charging modes that are available for almost any modern charger:
- Direct / Fast charge (Direct charge / Fast charge) – in this case, the battery is charged only by means of the main / discharge wire, which excludes the possibility of the charger to control the voltage of each cell throughout the entire charging process. Typically, this charging option proceeds faster than others, however, at the end of charging, the actual voltage of each cell may be different, and 100% charge level will not be reached.
- Balance charge – in this case, the battery is connected to the charger through the main / discharge and balancing wires, which allows the charger to control the voltage of each bank and charge them separately, maintaining an equal voltage throughout the process. This is the safest and most recommended way to charge Lithium Polymer batteries and eliminates, among other things, both the moment of undercharging each cell and the most dangerous moment of overcharging.
- Charging to storage mode (Storage charge) – in this case, the charger brings the voltage of each battery bank to 3.8-3.85V, which allows for careful storage of the battery on days when they are not in use. This approach is necessary because LiPo batteries cannot be stored in a fully charged state, or vice versa in a fully discharged state, as this adversely affects their internal resistance, which in turn determines their service life.
- Discharge – in this case, the charger will slowly discharge the battery (characterized by an extremely slow discharge process, even slower than charging).
Parallel charging is not the safest way to charge LiPo batteries, but probably one of the fastest ways for most RC hobbyists to get back into the sky. This approach allows you to simultaneously charge several batteries in turn. However, you should understand that you do this at your own peril and risk.
Place and facilities for safe LiPo charging
Approach the choice and equipment of the place for charging batteries wisely! No matter how pessimistic the recommendations below look, we recall that, by and large, the ignition of lithium-polymer batteries occurs only in cases of their improper operation, or as a result of force majeure / marriage, from which none of us is insured. Therefore, the more thoroughly you prepare for the possible risks associated with the operation of LiPo, the easier the consequences after they occur.
- Not the best place to charge and store LiPo is an apartment / house, but since this is the most common option among ordinary RC hobby users, care must be taken to purchase special equipment, including fire fighting (see points below).
- It is very important to charge the batteries in an area free from flammable objects and materials.
- The best option is to re-equip / retrofit the premises in accordance with the level of fire risk (recommended).
- For LiPo charging/storage, it is recommended to make/use iron boxes or boxes (preferably with separate walls and it is good if there is sand between the walls). As a mass-produced option, the simplest safe is perfect, or well-proven and time-tested branded solutions sold under the Batt-Safe brand.
- Do not trust the often offered on the market – “LiPo Bags”, as often they do not cope with the task assigned to them!
- It would be useful to install an iron container with a lid half filled with sand at the place of charging (the simplest example, a bucket, etc.). Firstly, sand acts as a simple and effective means for extinguishing / localizing a source of ignition (you can simply fill the battery with sand). Secondly, in the event of a fire, such equipment will allow you to safely localize the source of ignition by placing the battery in the container itself with sand, followed by closing the lid, thereby completely eliminating the spread of fire in the room. To capture an already burning LiPo, you can use a tongs tool with elongated handles.
- The presence in the room of primary fire extinguishing equipment, such as a fire extinguisher, has also not been canceled. To extinguish lithium, only fire extinguishers with a powder composition of LithX / Vekson-D3 (based on graphite / Various fluxes and graphite with water-repellent additives) or class D powder fire extinguishers are used. However, it should be noted that extinguishing with such compositions is more relevant for technical premises, since after application in an apartment / house, a detrimental effect of the powder on both humans / animals, and on interior items, electronics, etc. is possible.
- Fumes from burning lithium are poisonous, which predetermines the purchase of such respiratory protection equipment as masks, half masks, respirators, gas masks.
Demonstrative Approach to Security
Pay close attention to batteries when charging:
- Never leave rechargeable batteries unattended, as a rule, all fires caused by the ignition of LiPo occurred precisely because of the carelessness of the user!
- While charging, check regularly to see if the battery is getting hot or starting to swell, and if so, stop charging immediately!
- A healthy LiPo battery will never get hot during the charging process. If this fact takes place, then it is necessary to immediately stop the process and find out the causes of heating.
The result of carelessness
Recent bad experience. As the author himself explains, he is far from a beginner, he simply loosened control over rechargeable LiPo batteries. No one was injured as a result of the fire.
Other Notes on Safe Charging
Improper handling of LiPo batteries can cause a fire. Please take your time to read these safety instructions before using/charging batteries.
- It is recommended to charge the battery with a current of 1C or less (see the “C-Charge Rating” section above).
- Do not charge the battery immediately after use, wait until it has completely cooled down.
- Check that the settings of the charger correspond to the battery being charged (for example, check: the number of cans “S”).
- Never use or charge a damaged battery – do not charge it if it is swollen or has other visible signs of damage.
- Make sure the battery is not overcharged. Despite the fact that the charger monitors and does not allow the fact of overcharging, it is recommended to regularly check the current battery voltage with a voltmeter.
- Disconnecting the battery from the charger should be done by directly grasping the connector / connector itself. In other words, you should not pull the wires or the battery to disconnect, as this can lead to the separation of the supply / balance wires from the connector / s at the soldering points, which can subsequently lead to a short circuit of the battery, followed by fire.
- Do not leave the battery exposed to sunlight.
Recommendations for using LiPo
LiPo tester is a compact device that allows you to control the voltage of each cell of LiPo batteries in order to be aware of the uniformity of their charge level. If one of the cells has too low or high voltage compared to the rest of the battery cells (what in the RC hobby is called imbalance), then most likely this bank is experiencing problems, and you need to balance charge the battery before using it.
LiPo operating temperature range
- For mini quads max. LiPo battery performance is achieved at temperatures between 25°C and 55°C.
- Cold weather noticeably worsens the performance of LiPo batteries: the discharge rate and effective capacity decrease (up to 40%). Common symptoms when using LiPo in freezing temperatures are: shorter flight time, loss of power/pickup and severe voltage drop.
- For optimum performance, it is best if the battery is preheated to 30°C … 35°C before flying. To do this, it is enough to put the batteries in a warm place (for example, a pocket) or you can resort to the so-called “Heated LiPo Protective Bag”, the best offers of which have the ability to adjust temperature conditions.
- Also LiPo doesn’t like being too hot. Once the battery temperature reaches 60°C, it may swell and even catch fire.
When is the best time to end a flight?
This is one of the most common questions newbies ask: “When should I land?” Professionals recommend ending the flight when the voltage for each battery cell reaches 3.5V to 3.6V. Lithium-polymer batteries must not be discharged to zero, they must always remain at an acceptable charge level!
The chart below explains why. The fact is that the voltage in LiPo does not decrease linearly as the capacity is consumed, but drops sharply when it reaches about 3.5V – 3.6V for each LiPo element. And if you haven’t landed by then, you risk over-discharging your battery, and over-discharging your LiPo battery can permanently damage your battery and shorten its lifespan.
How to properly store batteries?
If you decide not to use the LiPo battery for an extended period of time (for example, longer than a week), you should:
- Charge the battery in the “Storage charge” mode up to 3.8V – 3.85V.
- Tape all LiPo connectors.
- Then put them in an iron box/box (mentioned above in the “Location and Facilities for Safe LiPo Charging” section) and store at room temperature.
- When the LiPo cell is charged to 3.8V – 3.85V, the charge level is approximately 40-50%, which ensures the most stable state of the LiPo battery. That’s why whenever you get a new battery from the store, it’s only half charged.
- Keeping a LiPo in a fully charged state is not only unsafe, it also reduces its performance.
- Do not use the so-called safe LiPo bags or LiPo Safe Bag for storing and charging lithium-polymer batteries, as a rule they do not cope with the task assigned to them (only an iron box)!
What to do with over-discharged batteries?
From the moment a LiPo battery has been completely discharged, time begins to work against it, as oxidative processes are launched in each bank, which gradually and irreversibly begin to degrade the overall performance of the battery. Therefore, the faster you connect it to the charger, the more likely it is to save the battery with minimal damage to its performance.
Often, chargers refuse to charge an overly discharged battery. Despite the fact that there are “artisanal” methods for restoring such batteries (not safe), professionals recommend that you stop using them!
Traveling with LiPo batteries
Most airlines and airports allow LiPo batteries to be carried in the passenger’s carry-on baggage. Here are a few tips to keep in mind:
- Check with the airline in advance about the possibility of transporting lithium-polymer batteries.
- Do not leave batteries in checked/checked baggage. Hand luggage only!
- Charge the battery to storage mode.
- Insulate all connectors / connectors of the battery with electrical tape and place them in an iron box.
- Never travel with swollen/damaged batteries!
What to do if the battery caught fire?
- Don’t panic and unplug all connectors.
- Use sand as the easiest and most effective way to put out a burning LiPo. Just fill the battery with sand. Or, as recommended above, immerse the LiPo in a specially prepared iron container with sand and cover with a lid.
- Wait until the fire goes out, the battery cools down and the smoke dissipates. Do not inhale smoke, burning lithium fumes are poisonous!
- Do not use water to extinguish lithium polymer batteries!
- Fire extinguishers only category “D”!
LiPo batteries have a limited lifespan due to the number of cycles. One cycle is equal to one charge followed by battery discharge. It is believed that with proper operation (mentioned above), LiPo batteries used to power radio-controlled models can withstand up to 300 cycles.
When to dispose?
There are no specific guidelines for when you should stop using a battery. Professionals dispose of the battery as soon as it noticeably ceases to give out its former potential, when the response of the drone to the movement of the throttle becomes less sharp, and the flight time is halved. Also, a weighty argument indicating that it is time to dispose of the battery is its internal resistance, which inevitably grows during the operation of the battery (see the section “Internal resistance” above). Swollen, damaged batteries are disposed of immediately.
How to dispose?
Before disposal, it is required to discharge the battery to a voltage value of 0V, which eliminates the possibility of battery ignition even if its integrity is destroyed. After that, you need to hand over the battery to one of the available collection points for used batteries. You can find out more about the points of acceptance and the rules for the delivery of used batteries here.
Several safe discharge methods are mentioned in hobby circles:
- Discharging with a charger in the “Discharge” mode (low current; example: at 1/10 C, a 3000mAh battery must be discharged with a current of 0.3A or 3000/10 = 300mA). However, many chargers have overdischarge protection and can discharge batteries to at least 3V. If so, consider discharging in the ways below. The discharge time by means of the charger is approximately one hour.
- Discharging with a small load (any current consumers; a popular way is with a light bulb or several at once, the best option is halogen lamps. LEDs are not suitable). You can also use any resistive load in place of a light bulb, such as a radial ceramic resistor. For example, for 2S or 3S Lipo, you can use 150 ohm 2 watt resistors. The discharge time for both methods is about an hour.
- By immersing LiPo in a water-salt solution until gas formation stops. The composition of the solution: for 1 liter of water – 2-3 tbsp. spoons of salt. Many users claim that this method is slow and inefficient. You will need an unnecessary plastic container. Discharge time is about 2 weeks.
So, in the presented guide, we have collected the most up-to-date information on terminology, design, selection, safe operation and disposal of LiPo powered FPV drones, however, we do not claim that this is all you need to know in this area. Summing up all of the above, we note that at the current time, lithium-polymer power sources are the best that technologies can offer us, which, although slowly, continue to improve. You have nothing to worry about if you follow the basic rules of operation and do not allow carelessness from the moment of selection to the moment of disposal of the LiPo battery. We hope the material we have collected was useful to you. We thank you for your attention.
Q. How dangerous are LiPos in use?
A. No more than any other power source, subject to compliance with the rules of operation. Marriage also predetermines the level of safety for future use, so it is recommended to purchase batteries only from trusted brands. As the saying goes, “the miser pays twice.”
Q. What brands does the RC community recommend?
A. The list of well-known and time-tested brands today includes: Tattu, Turnigy, Infinity, Dinogy, Luminier, GNB, URUAV, Acehe, XF Power, CNHL Ministar, RDQ series (if you are sure that someone is not on this list enough, let us know in the comments).
Q. Is a swollen battery dangerous?
A. Absolutely yes! Swollen batteries are not allowed for operation, are not repaired and are immediately rejected.
Q. What causes a battery to swell?
A. Battery bloating causes uncontrolled gas release, and since each can is hermetically sealed, bloating occurs. There are several reasons for swelling: damage, overheating, excessive charging current / overcharging or excessive (high current) prolonged discharge, as well as factory defects (typical for “no-name” batteries).
Q. How to avoid battery swelling?
A. Do not overload the battery – use a voltage alarm or monitor to control; Do not overheat (do not leave batteries in the sun or near a heat source); Never overcharge (Set your charger settings correctly and keep an eye on your charger while charging; Store your LiPo properly as we mentioned in this article.
Q. Do I need to resort to “Buildup / Acceleration / Break-in” of the battery?
A. The break-in procedure is a controversial topic in the FPV community. Essentially, this practice means that new batteries must go through a series of slow cycles (charges and discharges) before being fully utilized. However, many professionals do not see any obvious difference with this approach.
B. Other terminology related to LiPo batteries.
- Cut-off voltage – the voltage at which the battery is considered completely discharged; For LiPo, this threshold is set to 3V.
- Service life (Cycle life) – one cycle includes charging and discharging the battery. Service life refers to the total number of such cycles during which the battery will work.
- State of charge – current battery charge level from 0% to 100%.
- Burst C-Rating – the maximum discharge rate in a short period of time (usually within 10 seconds).
Q. What is the optimum voltage range for charging and discharging the battery?
A. The LiPo battery is designed to operate within the safe voltage range of 3 to 4.2V per cell. Discharging below 3V can result in permanent loss of performance and even damage to the battery. Overcharging above 4.2V can be dangerous and eventually cause a fire. Despite this, it is recommended to stop the battery when its voltage reaches 3.5V. For example, for 3S Lipo, the maximum voltage is 12.6V and you should land the drone when the voltage reaches 10.5V (i.e. at 3.5V per can).
Q. What is the internal resistance of a battery?
A. Internal Resistance (IR) determines the quality of a LiPo battery. The lower the value, the better. Higher internal resistance reduces the maximum current the LiPo can draw and increases the voltage drop. The internal resistance of a LiPo battery increases during operation, and the process itself is inevitable and irreversible. That is why, over time, batteries cease to give out their former potential. A large spread between the values of each jar indicates its poor condition, and the smallest one indicates a good one. The internal resistance is measured both by means of special tools – testers, and by means of some chargers.
Q. Which charger should I choose?
A. There are many different types of chargers on the market, so, as with the choice of batteries, the best and most reliable solutions are offered only by time-tested brands. The list of top brands includes: ProLead RC, SKYRC, EV-PEAK, Tenergy, ToolkitRC, HOBBYMATE, ISDT (if you are sure that this list is missing someone, let us know in the comments).
Q. What is the best charger charging mode for LiPo charging?
A. Balance charge mode – in this case, the charger controls the voltage of each cell and charges them separately, maintaining equal voltage throughout the process. This is the safest and most recommended way to charge Lithium Polymer batteries and eliminates, among other things, both the moment of undercharging each cell and the most dangerous moment of overcharging.
Q. How safe is parallel battery charging?
A. Despite the fact that parallel charging allows you to quickly and without problems charge several batteries at the same time, significantly reducing the tedious waiting time, this method is still considered not safe. In this connection, parallel charging is most relevant only in the field, where the possibility of burning expensive property is minimized.
Q. What is more reliable “LiPo Bags” or an iron box?
A. Of course, the advantage of iron boxes, which is stated by numerous test reviews. Today, tools such as “LiPo Bags” rarely cope with the task assigned to them, and even if they perform their functions, they are usually not suitable for subsequent use, which cannot be said about iron boxes, it is enough to clean them and they are back in service.
Q. What is the operating temperature range of LiPo?
A. For mini quads max. LiPo battery performance is achieved at temperatures between 25°C and 55°C. Cold weather conditions noticeably worsen the performance of LiPo: the discharge rate and effective capacity are reduced (up to 40%). Common symptoms when using LiPo in sub-freezing temperatures are shorter flight times, loss of power/pickup, and severe voltage sag. For optimal performance, it is advisable to warm up the batteries to 30°C … 35°C before flying (for example, put the batteries in your pocket or resort to the so-called “Heated LiPo Protective Bag”). Also LiPo doesn’t like being too hot. Once the battery temperature reaches 60°C, it may swell and catch fire.
Q. When is the best time to stop flying?
A. It is recommended to end the flight when the voltage reaches 3.5V to 3.6V per can. This is due to the fact that the voltage in LiPo does not decrease linearly as the capacity is consumed, but drops sharply when it reaches about 3.5V – 3.6V for each LiPo element. And if you haven’t landed by that time, you risk over-discharging your battery, and over-discharging your LiPo will permanently damage your battery and shorten its lifespan.
Q. Where to take used LiPo batteries?
A. You can learn more about pick-up points and return rules here.