If you’re new to the FPV/drone hobby, you’ve probably heard of LiPo batteries but might not be quite sure what they are or how they work. This beginner’s guide will teach you everything you need to know about LiPo batteries, from deciphering all the numbers to prolonging their life cycle. You’ll also learn about different types of LiPo batteries and which one is right for your needs. By the end of this guide, you’ll be an expert on LiPo.
- What is a LiPo Battery?
- What is the advantage of LiPo batteries?
- What do all the numbers on LiPo batteries mean?
- FAQs About LiPo Batteries
What is a LiPo Battery?
So, what are LiPo batteries? They are essentially a type of rechargeable battery that uses lithium-ion chemistry. This makes them lighter and more compact than other types of rechargeable batteries, which is ideal for use with drones and other RC vehicles where every gram can make a difference.
What is the advantage of LiPo batteries?
LiPo batteries (short for lithium polymer) can be charged relatively quickly and have a higher energy density than other types of rechargeables, meaning that they can pack more power into a smaller space. This makes them perfect for high-performance applications where every gram counts.
Lastly, LiPo batteries offer very good discharge rates. They can provide high levels of power when needed, making them perfect for use in R/C vehicles that require frequent acceleration or bursts of power output.
What do all the numbers on LiPo batteries mean?
The various properties of batteries are defined through a rating system. With these ratings, we can compare batteries and choose which is most suitable for the needs of our drone or RC vehicle.
There are three primary ratings that you need to be aware of.
The first rating is Voltage, which measures the work potential of the battery.
The second rating is Capacity, which measures how much energy the battery can store.
And finally, the third rating is Discharge Rate, or how quickly the energy can be drawn from the battery.
Let’s break it down and explain each….
The default resting voltage of a battery pack is called the Nominal Voltage. However, it’s worth noting that nominal voltage is not the same as the full charge voltage of the cell. LiPo batteries are considered full when they reach 4.2v/cell, and their minimum safe charge is 3.0v/cell. 3.7v falls right in the middle and thus became the nominal charge of the cell.
If you hear people talk about a “2S” battery pack, it means there are 2 cells in series in that battery. So, as the nominal voltage of a LiPo cell is 3.7V, a two-cell battery would have a voltage rating of 7.4V. A three-cell “3S” battery pack has a rating of 11.1V, and a four-cell “4S” has a rating of 14.8V, and so on.
The voltage of a battery pack is a primary factor in dictating the speed of your drone. A higher voltage will result in a higher RPM from the electric motor. Subsequently, this will cause the vehicle to go faster. Brushless motors are rated by ‘kV’ which represents revolutions per minute (RPM) per volt. Thus, a 3,500kV motor will spin at 3’500 RPM on a 1S LiPo battery, 25,900 RPM on a 2S, and 38,850 RPM on a 3S. So the more voltage you have, the faster you will go.
The capacity of a battery is measured in milliamp-hours (mAh) and tells you how much current can be drained from the battery to discharge it in one hour. 1000mAh is equivalent to 1 Amp Hour (Ah). Consequentially, the higher the mAH rating of your battery the longer you will be able to fly. However, there is a downside to large capacity batteries, higher mAh means bigger size and weight.
There is no standard capacity when using LiPo batteries with drones as they come in various sizes and power levels, and are used for varying reasons. Drone batteries can generally range anywhere from 300mAh all the way up to 30,000 mAh and beyond for some commercial/industrial drones, although most hobby pilots will never need anything near that capacity.
Discharge Rating (C Rating)
The C rating is one of the most important factors when choosing a LiPo battery. It determines how much energy the battery can discharge safely.
The main difference between batteries with different C ratings is that the higher-rated batteries don’t voltage drop (also known as ”voltage sag’) under load as much. A pack that can maintain a high and consistent voltage is better for powering multiple motors at once.
When it comes to flight times and motor performance, the higher a battery’s C rating, the more likely you’ll be pleased with the results. A 30C pack will outperform a 10C pack in power delivery.
Using the C rating, we can calculate the maximum current able to be safely drawn from a LiPo without damaging it. To calculate the max current draw, use this formula: Capacity x C-Rating equals max current draw…
Capacity (in Ah) x C-Rating = Max Current Draw
For example, let’s say you have a 2S 1000mAh 35C LiPo battery. The safe maximum current draw would be 1000mHa x 35C, which equals 35A.
(1000mAh) 1Ah x 35C = 35A
While it’s possible to draw more amperage from the LiPo in the above example (higher than 35A), it is not recommended. Doing so will overheat the battery and increase the internal resistance of the cells, which will shorten the battery lifespan or even damage it.
Batteries with a higher C rate are generally bigger and heavier than those with a lower C rate, even if those batteries are of the same capacity. When choosing the right LiPo battery for your drone, the C rating is an important consideration. If the C rating is too low, your battery could overheat, get damaged, or your drone won’t perform as well as it should. Conversely, if the C rating is too high, you’ll just be carrying around extra weight that does nothing for you besides reducing running time.
FAQs About LiPo Batteries
Here are some commonly asked questions about LiPo batteries and their use.
Are LiPo Batteries Safe?
The short answer is yes, LiPo batteries are perfectly safe for use if you take the necessary care and precautions. Improper use of LiPo batteries, however, can shorten their lifespan or result in a LiPo fire that can damage property or even worse, be deadly. To avoid this, you should follow safety advice.
Here are some safety guidelines:
The most important thing is to never leave a charging LiPo unattended. If you must leave the area for any reason, then stop charging. The majority of deadly LiPo fires occur during charging when people are not present.
- Keep a fire extinguisher nearby while charging.
- Never charge the LiPo inside the device it is powering–always remove it and place in a safe area.
- Before starting the charger, always check the connections.
- Always charge a LiPo on a non-flammable surface.
- Charge in an outdoor or well-ventilated area.
- Do not charge a damaged or a puffy LiPo.
- At no time should you short circuit the output of a LiPo; this is especially important during charging.
- Another safety measure is to keep children and pets away from the area where you are charging the battery.
- Try to avoid flammable liquids or objects whilst charging, and as aforementioned, never leave a charging battery unattended.
Where to store LiPo batteries?
LiPo batteries should be stored in a cool, safe place that is as fireproof as possible and away from the reach of children and animals. A LiPo storage bag would be preferable if you have one – if you don’t consider purchasing one for the peace of mind and welfare of yourself and your loved ones should the worst-case scenario take place. A LiPo bag won’t completely stifle the flames of a fire should one happen, but it will give you more time to react.
- Store LiPos in locations that are cool (not cold) and as fireproof as possible. The concrete in your garage, or in a metal box away from flammable objects are good places to consider storing them.
- Store LiPo batteries in dry, controlled places that are not too hot or not too cold,
- Some people like to store their lipos in ammo boxes.
Why Do LiPo Batteries Puff / Swell up?
LiPo batteries expand due to a process called “electrolyte decomposition” – the chemical breakdown of the electrolyte into its individual components, which are mostly lithium and oxygen. The polymeric electrolyte in LiPo batteries also produces carbon dioxide (CO2) and carbon monoxide (CO) when they decompose, and this is what causes the batteries to puff and swell. Here’s an in-depth article on the topic of LiPo battery swelling.
Will LiPo Batteries Freeze?
LiPos are not suited for cold temperatures. The discharge rate of a LiPo battery is significantly affected by its temperature. When a battery’s temperature drops below 10° C (50° F), you’ll notice a performance drop, and even more so as the temperature gets lower. The colder a battery gets, the more significant the drop in C rating and consequently, the performance.
Low battery temperatures will increase internal resistance and cause voltage sags, which in turn will result in shorter flight times, decreased speeds and lower overall power. Using, storing and even charging LiPos in cold conditions will decrease the life cycle and performance of a battery – and may additionally cause damage to your drone’s ESC capacitors.
What does LiPo battery stand for?
LiPo is an abbreviation of lithium-ion polymer.
Have any questions or comments about LiPo batteries? Leave a comment in the accompanying forum topic for this post.