Taking your drone out for its maiden voyage can be an almost spiritual experience as you watch this majestic aircraft follow your commands (hopefully) as you share in the Wright Brothers’ dream. However, if you fail to choose, install and maintain your LiPo batteries, your maiden voyage may crash and burn from first launch. And, we’re not using “burn” as a metaphor! While hobby-level drones still tend to offer short flight times, prosumer-class UAVs are staying aloft longer than ever thanks to the humble LiPo battery.
What is LiPo?
Just to be clear – we’re not talking about liposuction surgery that Fight Club so disgustingly depicted. LiPo means lithium polymer, and we’ll leave it at that. The purpose of this article is to provide a high-altitude overview of LiPo technology. You can find a deeper dig into the science with this excellent whitepaper by Jauch Technologies.
Drones and LiPo batteries make for a dynamic duo when it comes to providing longer flight times combined with lower weight and sharper flexibility. LiPo’s chemical composition allows for higher capacities and higher discharge rates. This means a properly maintained LiPo battery pack can deliver more “oomph” for your drone and keep it in the sky longer.
Unlike other rechargeable batteries, LiPo batteries hardly self-discharge at all. So, they can be stored over a period of 1-2 months and still be ready for flight.
LiPo chemistry, however, is a bit more volatile then other battery types so extra care needs to be taken when storing, shipping or transporting. An improperly maintained LiPo battery can be a fire hazard.
LiPo vs Lithium Ion
When researching LiPo batteries, you may run across the term lithium-ion battery. Are they the same? Yes and no.
Of course, both are composed of lithium (can you remember their number on the periodic table without peeking?). Both rely on chemical processes that can lead to fires if handled incorrectly. Lithium-ion batteries are usually encased in a more rigid structure compared to LiPo.
Many Li-ion models resemble a slightly larger AA battery (cell) and multiple cells are often placed in a hard-plastic pack for higher-energy use (as found in laptops). Li-ion batteries are mainly found in power tools, computers and mobile phones.
A stark difference between the two boils down to flexibility (and don’t boil either, please). As noted above, Li-ion are manufactured in more rigid cases and can’t be molded into as many configurations as LiPo.
LiPo batteries are not prong to leakage because they are usually encased with an aluminum plastic film that is more robust than cases found in Li-ion. LiPo offers a tinier thickness – down to less than 1 mm.
Depending on the shell, LiPo batteries are typically 20-40 percent lighter than their chunkier cousin. They also offer higher power output and higher capacity. In short, LiPo is to Li-ion what Arnold Schwarzenegger is to – well – me.
Which LiPo Battery is Best for your Drone?
As with so many questions in life, the answer is “depends.”
Unless you are building a DIY drone, your battery choices will be limited by the manufacturer. Most drones can handle batteries that offer a variety of total flight duration, but your choice will still be limited by the maximum takeoff weight of your drone. It should go without saying – greater flight duration equals higher cost.
Choosing the right battery is like choosing the right automobile – some people want get-up-and go; others want fuel efficiency. Are you into FPV racing? Your LiPo will need to offer a higher discharge rate to get that extra burst of speed – look for a higher C rating. For longer flight times, large capacity batteries may be useful but, again, more duration means a heavier battery and the trade off could end up being a wash.
How many should you own? Depends on how often you fly and what kind of mission you run. In the field, it’s a good idea to have a few backups on hand. That also means buying a couple of chargers, at least.
Storage, Shipping and Disposal
In case we haven’t said it enough – LiPo batteries are safe but volatile if mishandled. Always store them in a fireproof place – you can even buy special fire-resistant bags. Some experts recommend storing them in a metal ammo box. Store LiPo’s at room temperature at about 50 percent charge.
Lithium metal (nonrechargeable) cells and batteries and lithium-ion (rechargeable) cells and batteries are mailable in limited quantities domestically via air or surface transportation when they are installed in or packed with the equipment they are intended to operate. Unless otherwise excepted, lithium metal and lithium-ion batteries (without equipment) are mailable in limited quantities domestically via surface transportation only, according to the U.S. Post Office.
FedEx and UPS offer interactive, step-by-step guides to determine the best way to ship LiPo.
Before disposing of your LiPo, you should completely discharge it. After the charge is 100-percent empty, you may dispose of the battery at your local recycling center or check out Call2Recycle for other options.
If the battery is burned, leaking, punctured or corroded immediate action is required. Call2Recycle recommends the following steps:
“Place the battery or device in a non-flammable material such as sand or kitty litter as soon as possible. Check the Consumer Product Safety Commission or manufacturer web site or visit the retailer you purchased it from to see if the battery or device has been recalled. If it has, follow the instructions.
“As an alternative, place the battery or device (one per bag) in a clear plastic bag and take it to your municipal household hazardous waste (HHW) recycling center. You can also contact a local Call2Recycle drop-off site to see if it accepts damaged batteries. Do not place them in the trash for any reason.”
Traveling With Your LiPo
You’re likely traveling with your drone because you plan to use it and make the hassle of transporting it worthwhile; as such, one battery will rarely cut it. It’s important for drone pilots to know the rules and requirements before packing equipment for a trip, as the last thing you want is surrender the brand new LiPo drone batteries you dropped a couple-hundred dollars on to your friendly, local TSA agent.
In March 2019, the FAA announced new regulations for transporting lithium batteries on planes:
“[The new rule] prohibits the transport of lithium ion cells or batteries as cargo on passenger aircraft. In addition, the [rule] requires lithium ion cells and batteries to be shipped at not more than a 30 percent state of charge aboard cargo-only aircraft.”
Checked Bags & Carry-On Luggage
Passengers are now required to transport detached batteries with them in carry-on luggage. According to the FAA, “Spare (uninstalled) lithium ion and lithium metal batteries must be carried in carry-on baggage only. When a carry-on bag is checked at the gate or at planeside, all spare lithium batteries must be removed from the bag and kept with the passenger in the aircraft cabin”. This essentially means, if flying alone, you are allowed to bring with you a maximum of three LiPo batteries. Plan to pack your drone, with battery installed, in a checked bag. If you happen to be flying with non-drone pilot friends or family, you can always ask them to carry some of your batteries for you.
Wattage Limits
Lithium batteries with more than 100 watt hours may be allowed in carry-on bags with airline approval, but are limited to two spare batteries per passenger.
The Great Commandment for UAV owners is simple: “Know Thy Drone.” That means understanding the law, the basics of flight, electronics, parts and safety. Having a keen understanding of all things batteries makes up a large portion of “knowing thy drone.”
LiPo Terms
Like any complex technology, LiPo battery use requires some familiarity with a few key terms.
Cells and Voltage
LiPo batteries are assembled using rectangular cells that are connected to produce a certain voltage. One cell represents around 3.6V; 2 cells, 7.2V and so on. The number of cells for your off-the-shelf UAV will be determined by the size and design of the battery compartment. DIY pilots will, of course, have more options
Obviously, the greater the number of cells, the higher the voltage and the longer the flight time. As an example, a DJI offers a four-cell LiPo battery for the Mavic 2 at 14.4V for a flight time of 31 minutes.
Capacity
Usually measured in milli-amp hours (mAh), capacity determines how long the battery can fuel the drone’s motors. Easy math – the higher the mAh, the longer flight. But there is a trade-off – a higher capacity means a heavier battery. Another benchmark – DJI offers a 15.2V LiPo battery for the Phantom 4 at a capacity of 5870 mAh and a weight of about one pound. This will translate to about 30 minutes of flight time.
Discharge Rate
A LiPo battery’s discharge rate determines its rate of energy extraction that feeds the drone’s motors. This may be one of the most important terms to understand – a drone motor that draws too much juice (and damages the battery) is heading for a dirt nap.
Discharge rates are measured by C rating. As with most LiPo terms, a higher number equals a heavier battery. Once you know the C rating, you can calculate estimated flight times by first finding the battery’s maximum continuous amp draw (A).
To make the calculation: multiply the C rating by the mAh (converting the four-digit number to two digits). This will provide the battery’s “A” amp draw.
Example: a 5870 mAh with a 10C rating would have a 58.7 A (amp draw).
Once you have these numbers, you can plug them into an online calculator to estimate flight time for your LiPo battery.
We hope this guide has got you amped up, charged up and ready to take on that challenge. If you are interested in dronegenuity aerial photography or drone pilot jobs, or if you’d like to get more great drone industry content from dronegenuity, simply follow us on our social media channels: YouTube, Twitter, Facebook, and Instagram, and subscribe to our mailing list for regular updates.
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