LiPo batteries are incredible power source for FPV drones, they are able to store and deliver a large amount of energy, but when LiPo batteries are not handled properly they can be dangerous. In this guide you will learn all the basics of LiPo batteries for FPV drone, how to charge them safely, and how to store them when you are not using them.
Disclaimer: All information on this page should be considered as general advice. Ensuring battery safety is your own responsibility and you should use the information on this page at your own risk.
Are LiPo Batteries Safe?
When you are treating LiPo batteries properly, they can be perfectly safe.
There are many reasons why LiPo batteries might catch on fire. That tends to only happen when you don’t handle them properly or when they are physically damaged. If you’re gentle and careful with your batteries you should be okay.
What LiPo Should I Buy?
Maybe you are not interested in learning about LiPo, and just want to know what battery to get? Here are the batteries I have tried and recommend:
- For 5″ FPV drone: Best 4S Lipo batteries, and Best 6S LiPo batteries.
- For Micro drones (Tiny whoops, 2″, 3″, 3.5″): Best LiPo Battery for Whoop & Micro Quad (1S, 2S, 3S, 4S 250-650mAh)
However I suggest going through this article carefully to learn about how to handle LiPo. Bad practices can severely shorten your battery lifespan, or even result in a deadly LiPo fire in extreme cases.
The Basics of LiPo Battery
Lithium polymer batteries, more commonly known as LiPo, have incredible power to weight ratio which makes them a great candidate for FPV drones.
In order to select the proper LiPo battery, you will need to learn how to read and understand its specifications and basic terminology which I will explain now.
LiPo Battery Voltage
LiPo batteries exist in cells, each LiPo cell has a nominal voltage of 3.7V. This is the voltage number LiPo battery use on their labels.
LiPo battery is designed to operate within a safe voltage range, between 3.0V to 4.2V. Over-charging above 4.2V is dangerous and it could cause a LiPo fire. Discharging below 3V can cause irreversible performance loss or even damage to the battery. However the general consensus is to stop discharging when the battery reaches 3.5V per cell in order to prolong battery lifespan.
A LiPo battery can have multiple LiPo cells, common LiPo batteries for 5-inch FPV drones are 4-cell (or 4S) and 6-cell (or 6S). When higher voltage is required, LiPo cells can be connected in series to form a bigger, higher voltage battery.
Battery voltage has a direct effect on how fast the motors can spin, therefore you could use a higher cell-count battery to increase your drone’s power (assuming the electronics in the drone support the higher voltage). However, adding more cells to a battery also means it’s heavier.
In the hobby, we don’t normally refer to the total battery voltage because it’s mouthful, we just call them by the number of cells, or how many “S”:
- 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
For example, we call a 14.8V battery a “4-cell” or just “4S” battery.
When you connect two identical batteries in series, it does not change its capacity, but it doubles the voltage. For example, by combining two 2S 1000mah in series, you will get a 4S 1000mAh battery. But if you connect them in parallel, you will double its capacity but the voltage stays the same, ie. it becomes a 2S 2000mAh pack.
The capacity of a LiPo battery is measured in mAh (milli-amp hour), it indicates how much current you can draw from the battery continuously for an hour until it’s empty. Note that, 1000mAh = 1Ah.
For example, for a 1300 mAh Lipo (or 1.3Ah), it would take an hour to be completely discharged if you draw a constant 1.3A current from it. If the current draw doubles at 2.6A, the duration would be halved (1.3/2.6=0.5). If you draw 39A of current non-stop, this pack would only last 2 minutes (1.3/39=1/30 of an hour).
Increasing your battery capacity might give you longer flight time, I say might because the battery also gets heavier and bigger which is a tradeoff. Weight has an significant impact on an aircraft’s flight time, it’s important to select a battery with good balance between capacity and weight for optimal efficiency. I wrote a guide on how to build a simple mathematical model to find the optimal Lipo capacity for good flight time. But really it’s not as technical and confusing as that, the best way is just to follow what other people are using and you will be fine. People in the hobby have pretty much figured out the optimal capacities for the different drone sizes over the years.
Higher capacity battery could also give you higher discharge current as explained in the next section.
C Rating is an indicator of how much current you can safely draw from a LiPo battery without causing damage, which in theory, can be calculated by:
Maximum Current Draw = Capacity x C-Rating
You could draw more current than the C-rating specifies, but it’s not recommended as the battery can overheat and that will over time increase the internal resistance of the cells faster, which subsequently shortens battery lifespan or even cause a thermal runaway (catching fire) in extreme cases.
Batteries with higher C-rating tend to be heavier and larger even at the same capacity. Here’s an example, both of these batteries are 4S 650mAh, but the one on the left only weighs 60g, while the one on the right weighs over 86g and is noticeably bigger.
A higher C-rating battery definitely has better performance especially on a power-hungry drone, but it’s not always the better choice. For example, on a low power cruiser, the extra power from a higher C-rating battery might not be necessary, while the additional weight would be counter-productive and results in less flight time. It’s all about using the right tool for the job.
Although C rating could be a useful tool, unfortunately it has become mostly a marketing tools in recent years, so you should take C-Rating as a grain of salt. Brands might inflate their C-rating numbers to different degrees, so it’s pretty meaningless to compare it between brands, but it still can be helpful for choosing battery from the same brand assuming they follow the same standard. As long as you are getting batteries from the brands we recommend, C-rating isn’t really something you should worry about.
All electrical components has resistance, even a piece of wire has resistance, so is a battery. The resistance in a battery is called internal resistance (IR).
Internal resistance can be used to measure how healthy a LiPo battery is, it’s a useful indicator to help decide if you should retire your LiPo battery. Lower IR means the battery can deliver power to your FPV drone more effectively.
IR in LiPo cells is increasing slowly with time and usage which is inevitable and irreversible. The following bad practics can speed up the aging of your LiPo:
- Over-discharging and over-charging
- Pushing the battery too hard by discharging at a current higher than what it’s rated for for an extended period of time
The biggest factor that affects the maximum discharge rate of a battery would be internal resistance of the cells. When your battery has high internal resistance, battery voltage will drop more noticeably as you increase throttle – a common issue known as “voltage sag”. And with the voltage decreases, the motor will start to lose RPM and ultimately the drone would feel less powerful and responsive.
Some batteries are designed for low current applications (for example a battery with 8C or 10C rating for powering a radio), IR will inherently be higher. 18650 Li-ion batteries have much higher IR than a typical LiPo batteries too which is completely normal, so do not worry!
All LiPo batteries come with 2 sets of wires/connectors: the discharge connector (main lead) and balance connector (balance lead). (except for 1S batteries which only have a discharge connector).
The discharge lead typically consists of a thicker red and black wires, which is used to power the FPV drone.
There is also another set of smaller wires going to a smaller white connector, that’s the balance lead. The number of wires depends on the number of cells in the battery.
The most common discharge connector would probably be the XT60, these are mainly used in 5″ FPV drone or larger. For smaller drones, the smaller version of XT60, XT30 is often used. They have basically the same shape just different sizes and current rating.
Other battery connectors you should know about are in this table. There are some other connectors too but they are rarely used in FPV drones and equipment.
|PH2.0 and BT2.0||1S|
|XT30||2S, 3S, 4S|
|XT60||3S, 4S, 5S, 6S|
This article gives you more insight into electrical wires and connectors.
LiPo batteries with more than two cells will always have a balance lead, which is for monitoring and balancing cell voltages. The official name of the balance connector is JST-XH.
You will need to connect the balance lead to the charger when charging, this allows the charger to check and balance the voltage of each cell during charging. IMPORTANT, always plug in the balance lead before charging!
The number of wires in a balance lead starts at 3 for a 2S LiPo, and that number increase by 1 for every increment in cell count:
- 2S – 3 wires
- 3S – 4 wires
- 4S – 5 wires
- 5S – 6 wires
- 6S – 7 wires
It’s not uncommon to have your balance lead damaged by the spinning propellers during flight, this post explains how to repair broken balance lead.
LiHV is a special type of LiPo battery, HV stands for “high voltage”. They are more energy dense than traditional LiPo battery, and allow to be charged up to 4.35V per cell (as opposed to 4.20V). However there are mix reviews out there regarding the longevity of LiHV, as they might have decrease in performance sooner than normal LiPo’s. In this post I compared a LiHV battery with a LiPo in terms of performance. However they are a very popular choice currently for 1S Tiny Whoops.
How To Choose LiPo Battery
If you take my LiPo battery recommendations, then you don’t need to worry about all the calculations.
- For 5″ FPV drone: Best 4S Lipo batteries, and Best 6S LiPo batteries.
- For Micro drones (Tiny whoops, 2″, 3″, 3.5″): Best LiPo Battery for Whoop & Micro Quad (1S, 2S, 3S, 4S 250-650mAh)
Avoid “no-name” batteries and stick with reputable brands. Just to name a few:
- GNB (Gaoneng)
- CNHL (China Hobby Line)
- Lumenier (GetFPV)
- Rebel Batteries
- Tattu R-Line
If you have a custom drone that doesn’t fit in any of the above categories, then you can choose a suitable battery by following these steps.
Work out drone current draw
Once you have decided on motors and propellers size, you should be able to find thrust data for your motor and what current it will draw for the propeller sizes that it supports. For example, for this motor with 5040×3 props, at 100% throttle it draws up to 36.74A.
The total max current draw for a quad of 4 motors would be 36.74 x 4 = 146.96A at 100% throttle. If you want to play safe, you could just use this number and find a battery that has high enough C-rating. But for me, I usually reduce it by 30-40% because first of all, we rarely flying at 100% throttle for more than a few seconds (for example I personally mostly fly at only around 40-60% throttle). And secondly, motors draw much fewer amps in real life than in static thrust tests because of the moving air.
There would be current draw from other components, but it would be insignificant compared to the motors so you can usually just ignore it.
Choosing optimal battery capacity
Now you need to work out the suitable battery capacity, which depends on the size of your quadcopter, and C rating required. Here is the general guideline I personally follow:
For 4S LiPo:
6 inch: 1500mah - 2200mah 5 inch: 1300mah - 1800mah 4 inch: 850mah - 1300mmah 3 inch: 650mah -1000mah
For 6S LiPo:
6 inch: 1200mah - 1500mah 5 inch: 900mah - 1300mah 4 inch: 550mah - 900mmah 3 inch: 400mah - 650mah
From there, we can calculate the C rating requirement using this formula:
C Rating = Current Draw / Capacity
How to Charge LiPo
Get A LiPo Charger
You’ll need a charger specifically designed for LiPo batteries due to the strict charging requirements lithium polymer batteries have. You can learn about how to choose a decent LiPo charger in this buyer’s guide.
If that’s too much information to digest, you can also just jump straight to my LiPo charger recommendation and pick one that meets your needs.
The following information will only apply to you if you got one of the chargers from my recommendations.
Connecting a LiPo to a Charger
On most modern LiPo chargers, charging LiPo batteries cannot be easier. Usually, all you need to do is to plug in the XT60 and balance connectors, set a few parameters and you are good to go.
- Balance charge – while charging the battery, the charger monitors the voltage of each cell and keep them balanced. This is the safest and most recommended way of charging your LiPo battery
- Storage charge – The charger brings each cell to storage voltage (which is 3.80V – 3.85V depending on the charger)
- Discharge – The charger attempts to drain the Lipo battery (it can be extremely slow depends on the discharging power of the charger)
Why balance charge?
Always plug in the balance lead before charging.
Every cell in a battery is slightly different. After a flight, you might find that the cell voltages are all different. If we were to charge a battery with imbalanced cell voltages without plugging in the balance cable, chances are some cells might end up under 4.2V and some OVER 4.2V which is dangerous.
On most modern LiPo chargers, balance charging is the default and only charging mode. If you have a cheap/old charger that lets you charge without the balance lead, throw it away right now and get a proper charger! That’s not safe at all!
How fast can I charge?
It’s recommended to charge LiPo at 1C or lower as it puts the least amount of strain on the battery. That means for whatever battery you have, set the charge current to 1 times the capacity. For example, for a 1500mAh LiPo, charging at 1C means setting the charge current to 1.5A (1C x 1500mA), and for a 900mA, that is 0.9A, and so on.
Charging at 1C means it will take roughly an hour to fully charge the battery from empty.
Many batteries nowadays allow faster charging, such as at 3C or even 5C. Make sure you understand the specs of your LiPo before charging at such high rate. If in doubt just charge it at 1C, charging your battery at higher C increases the risk of LiPo overheat/fire.
Choose Location Wisely
It is very important to charge your batteries in an area clear of flammable items and materials. If you are charging indoor, try to do it close to a window or door so there is a chance you can throw the battery out quickly if fire happens.
I personally put my batteries in an ammo box (buy on Amazon) during charging and for storage. Some even build a fire-proof bunker for it. DO NOT trust “LiPo Bags”, they might slow down a LiPo fire, but they won’t contain it completely.
Always have a fire extinguisher nearby when charging.
Never charge LiPo battery unattended
If you want to leave the room, then stop charging. Most of the LiPo related fires I’ve seen are because the person left the room while charging. You should NEVER charge LiPo battery unattended! During charging, regularly check LiPo temperature, they should stay cold, if it gets warm or starts to swell then you should stop charging and investigate, it’s likely to be a faulty LiPo and needs to be retired, or you might be overcharging it, or you are simply charging too fast.
Other safety rules
Incorrect handle of LiPo batteries could potentially cause fire. Please take your time to read through these safety rules before handling/charging batteries.
- Pick up LiPo battery by the body, not the wires which could be pulled off from the fragile solder joints
- Don’t charge your battery immediately after using it, wait until it’s completely cool down
- Never use or charge a damaged/swollen battery
- Ensure the number of cells and battery type are set correctly on your charger before charging
- Never over-charge, although this is normally taken care of by the charger, it would be a good idea to check cell voltages regularly
- Don’t leave battery under the sun
- Always remove battery from the device it’s powering and place it in a safe area before charging
- Never short the outputs of a battery at all times
Parallel charging might not be the safest way of charging LiPo batteries, but it is a fast way to charge multiple batteries at the same time. I have a whole tutorial explaining how to parallel charge.
Charging 1S LiPo batteries
Charging tiny 1S batteries can be slightly different than charging the bigger packs. You can perhaps charge multiple 1S batteries using a parallel board (basically just combining them as one big 1S battery). But I think the most effective way of charging them is getting a dedicated 1S battery charger or charge board. Here are my 1S batteries charger recommendations.
How to use LiPo Batteries Safely
Don’t leave them fully charged or empty for long
It is best to use any fully charged LiPo as soon as you can, and return it to storage voltage when it’s done. That is because when a battery is not at its storage voltage, it’s constantly degrading over time faster. In general most people find leaving batteries fully charged or discharged for a few days acceptable. But if you don’t plan to fly for longer than a couple of weeks, it’s probably best to put your batteries on storage charge. You can do this easily on most modern chargers, though discharging can be extremely slow, you might want to consider getting a dedicated discharger if you do this often.
FPV drone LiPo batteries has the best performance between 30°C to 60°C.
Cold weather is a performance killer to LiPo batteries, you have worse voltage sag and flight time. Try to keep your batteries warm before a flight (e.g. put them in your pocket). Here are some more tips about how to fly FPV in the winter.
LiPo doesn’t like it too hot either, when it gets too hot they could start to swell and even catch fire. So make sure you don’t leave them under the sun in the summer!
When to land
You should land when your battery voltage reaches 3.5V to 3.6V.
You could keep flying until voltage is even lower, but it puts extra strain on the battery and might shorten lifespan faster. All cells are different in a battery, when you give the drone a burst of throttle the battery will sag and some cells might sag more than others and go below the safe limit and risk causing damage to those cells. Landing a bit early at 3.5V reduces the chance of that from happening.
Another reason is that the voltage drops a lot faster below 3.5V, if you keep flying you can risk over-discharging your battery before you can land safely. Over-discharging can cause permanent damage to the battery, and shorten battery life.
How to store LiPo
As mentioned earlier, if you decided not to use a LiPo battery for a long period of time (longer than a few week for example), you should
- Storage charge it to 3.8-3.85V
- Store it in a fireproof place (in LiPo bags, ammo box etc)
- Store it at room temperature – too cold is bad for lifespan and too hot is not safe
When a LiPo cell is around 3.8V-3.85V, it has roughly 40% to 50% charge left, and this is where the most stable state is for a LiPo battery. This is why whenever you receive a new battery from a shop, it comes half charged.
LiPo safe bags
LiPo bags are made of cloth, usually with a metallic compound woven into them, generally have either a zipper or a Velcro fastener. They are cheap and light-weight storage for battery transportation, while they might be able to slow down a LiPo fire, they are not effective for stopping or containing LiPo fire. I would recommend using metal ammo box instead for long term storage. But LiPo bags are relatively affordable and still better than nothing.
Get your LiPo bags from:
- Banggood: https://goo.gl/vbnErt
- Amazon: https://amzn.to/40c7qDN
- GetFPV: https://oscarliang.com/product-czrh
- RDQ: https://oscarliang.com/product-eie5
- AliExpress: https://s.click.aliexpress.com/e/_DePGYer
Before using ammo box for storing your LiPo batteries, make sure you remove the rubber seal on the lid (just pry it off with a screwdriver). And if possible, drill a couple of small holes for the air to escape when fire happens (or make sure it’s not tightly shut), so pressure doesn’t built up inside an air-tight metal box.
Get your Ammo Box from:
What to do with over-discharged LiPo
When a LiPo battery is completely discharged, it oxidizes the cells overtime and it causes reduction in performance permanently. However, if you can catch it quick enough you can usually save the battery without too much damage done to performance.
Chargers might be unable to recognize an over-discharged battery due to cell voltage being too low. My advice is to discard that battery. However there is a way to rescue an over discharged LiPo, but do so at your own risk.
Travelling with LiPo
Many airlines and airports allow LiPo batteries in passengers’ hand luggage. There are a few things to bear in mind:
- Always check with your airline regarding travelling with LiPo batteries
- Do not carry LiPo batteries in your checked baggage
- Put your batteries in storage charge
- Tape or cover the connectors and store them in a LiPo safe bag
- Never travel with damaged batteries
Please see my guide on “How to travel with mini quad and LiPo batteries” for more detail.
What to do when LiPo is on fire?
- Don’t panic, unplug all connection first if possible
- Use fire extinguisher
- If that’s not an option, sand is also an effective way to put out LiPo fire, cover the burning LiPo with sand
- do not breath in the smoke, just wait until the fire goes out and the battery is cool
- Do NOT use water ever
When to retire LiPo
LiPo batteries have a limited cycle life, every time you charge and discharge it, it is 1 cycle. It’s said a LiPo battery for RC models could be used over 300 cycles if looked after properly (by following the rules we have mentioned above). But for me it would be a miracle I don’t damage it before that :)
There isn’t really a rule that says when you should throw a battery out. But LiPo can lose “punch” and capacity as internal resistance building up over time, therefore IR is a good indication of battery health.
I would definitely dispose it if it becomes dented from a crash, or when it’s puffed like a balloon.
In this article I explain a bit more when you should retire/dispose LiPo battery.
How to disposal LiPo
Old and damaged Lipo batteries should be disposed properly. See this article to learn about the difference ways of disposing LiPo in this article. One thing I need to stress is, never puncture LiPo batteries, it will cause fire!
Here are a list of common questions from hobbyists.
Are Swollen (puffed) LiPo’s dangerous?
Yes, swollen LiPo batteries are not safe to use or store.
What causes LiPo batteries to go swollen?
LiPo swells because gas get trapped inside the cells. This is a natural thing to happen, physical abuse (such as damage, overheating or over-discharging) can cause the battery to generate more gas.
Can I fix puffed LiPo?
No you can’t. Once LiPo’s gone swollen it’s irreversible. Dispose it properly as soon as possible.
How to avoid Swollen batteries?
- Do not over-discharge – use some form of voltage alarm or monitoring
- Don’t overheat – avoid leaving batteries under the sun or close to heat source, don’t over-load the battery
- Never overcharge – setup your charger properly, and keep an eye on the charger while charging
- Store your LiPo properly as we’ve already mentioned in this article
Does new battery need to be broken in?
Break-in procedure is a controversial topic in the FPV community. Basically it’s a practice that suggest new batteries need to go through a series of slow cycles (charge and discharge) before putting into full use. I personally tried it and didn’t find any noticeable difference. See this forum thread for the discussion.
- Cut-off voltage – the voltage at which a battery is considered discharged completely; For LiPo it’s 3.0V
- Cycle life – 1 cycle is when you charge and discharge a battery. The cycle life is the total number of cycles the battery will last
- State of charge – the energy level of a battery from 0% to 100%.
- Burst C-Rating – the maximum discharge rate over a short period of time (normally within 10 seconds)
Congrats you made it!
Hopefully you learned something about LiPo batteries and how to use them safely. However I make no claims that this is all you should know. Please go and do more research if you are feeling uncertain.
- Feb 2017 – Article created
- Aug 2017 – Added “how to choose lipo”
- Sept 2018 – Added “is LiPo safe?”
- May 2019 – Updated Explanation of Cell Count and IR, updated section “how to charge”
- Jan 2023 – Updated guide