Complete Guide to LiPo Batteries & Charging

It is important for anyone looking to get into the hobby of flying quadcopters to have a basic understanding of LiPo batteries. These Lithium Polymer batteries (LiPo for short) are the type of battery that almost all drones on the market today use. This article will provide you a basic walkthrough to help you understand this popular type of battery. Lets dive into the fundamentals of charging, storage and everyday use.

This article is part of a series that covers the entire concept of quadcopter parts, how they work, and how they come together. For further reading, see the master article: Components & Anatomy of an FPV Quadcopter

Note: This article references batteries used in micro quadcopters and FPV miniquads. The information found here applies to all LiPo batteries regardless of their application.

Table of Contents

• What are LiPo Batteries?
• LiPo Battery Safety
• How to Charge LiPo Batteries
• Safe Storage & Use
• Travelling with LiPo Batteries

What are LiPo Batteries?

LiPo batteries are a high capacity, lightweight, and high discharge batteries. These batteries have enabled modern radio control flying as we know it now. These reliable power sources are made in almost any shape or size. They provide a high power output for their weight. They also have no memory effect from charging and discharging. A properly cared for LiPo can last for upwards of 400 charge cycles, and some manufacturers even claim to see 500 or more cycles.

Battery Ratings

All LiPo batteries are classified using the same rating system. This system will help you determine how many volts the battery puts out (cell count), how much power the battery can hold (capacity), and how quickly the battery can output its power (discharge or C-Rating). Lets take a look at what each of these means.

Cell Count / Battery Voltage:

A battery can be made up of multiple cells hooked together in a series. This is represented by a rating like 4s which represents 4 cells in series. Each cell has a nominal, or resting voltage of 3.7 volts. The voltage rating is declared as the total resting voltage of all the cells combined. In our example: 4 cells x 3.7 volts = 14.8 volts total.

Being connected in series means each cell is connected to the next in a 'line'. This means the negative terminal of cell 1 is connected to the positive terminal of cell 2 and so on. Speaking from a feel perspective when flying quadcopters - larger cell count batteries will give you more punch.

Here is a reference chart for common voltages up to 6 cells:

• 1 Cell = 3.7v
• 2 Cells = 7.4v
• 3 Cells = 11.1v
• 4 Cells = 14.8v
• 5 Cells = 18.5v
• 6 Cells = 22.2v

Capacity (mAh):

The amount of energy a battery can store is rated as milliamp hours  or mAh. The total storage will determine how much flight time you have. There is a give and take here as more mAh requires a larger battery which weighs more. FPV mini quads for racing will normally use batteries with between 1000 - 1500mAh capacity.

To determine the Amp hours, use the following equation: 1300 mAh / 1000 = 1.3 Ah

Discharge Rating (C Rating):

The discharge rating or C rating (C standing for Capacity) is a measure of how quickly the power can be extracted from the battery without damage. In order to determine the maximum safe draw in Amps you can use the following calculation using our 60C battery above:

1.3 Ah x 60C = 78A

C Rating is often over-hyped and more often than not the overall quality of your battery has more impact on performance. Focus on battery quality / C rating balance rather than just raw C rating.

Battery Leads & Connectors

Each battery will have one or more sets of wires (called leads) which are connected to the cells in the battery. There are two types - main leads and balance leads. The main leads connect to the positive and negative ends of the battery series. The balance leads are connected between

Single Cell Connectors

Two Types of 1S LiPo Connectors

Single cell LiPo's only have one set of +/- leads coming from the battery. This is because the battery is a single cell and does not require an additional lead to balance the voltage between cells. These single cell batteries normally use a small, two slot JST connector. Some batteries have the JST connector mounted to the battery, some connect it to the end of wires.

Multiple Cell Connectors

2 cell batteries and above will have two sets of wires (leads) coming from the battery - a main lead and a balance lead. The main lead is connected to the ends of the series connection on the appropriate positive and negative connection points. Most FPV miniquads are going to be using the yellow XT60 male connectors on the main leads. The balance lead connects to the master +/- leads as well as at the connection point between each cell.

LiPo Battery Safety

Before we talk about charging and discharging, we need to talk safety. The potential energy within a lithium polymer battery can lead to very dangerous situations if proper care is not taken. We've collected a series of warnings and recommendations that you should take very seriously.

• Never leave charging LiPo's unattended.
• Always charge and store LiPo's in a fireproof 'safe bag'.
• Never puncture a LiPo battery.
• Store at room temperature, never in extreme heat or cold (don't leave them in your car!).
• Be sure to properly connect your battery leads to any piece of equipment be it a charger or quad. Connecting to the wrong balance port or reversing polarity is very bad. Take extra care if modifying a battery lead that you observe polarity.
• Take extreme caution with batteries that have suffered damage in crashes. Monitor them closely on the next charge and storage. If ever in doubt, discard.
• Be conservative with charge rates - we recommend charging at 1C.
• Monitor leads and wires for damage. Properly maintain / fix any damage that does occur.
• Properly discard batteries by taking them to a store like Batteries + Bulbs. Never throw old batteries in the trash.

How to Charge LiPo Batteries

Charging LiPo's requires that you have a digital battery charger of some type. There are many options out there with varying feature sets. These chargers allow you to safely monitor and charge many types of batteries including LiPo, NiCd, NiMh and more. They include important features like short circuit prevention, individual cell monitoring, configuration warnings, overheating prevention, and an automatic shutoff.

Types of Charging

• Balance Charge - during a balance charge, your charger monitors the voltage within each cell and tries to maintain an even comparable voltage. This type of charging should be used most often - especially when a battery is new.
• Charge - this type of charging does not monitor the voltage of each cell in the battery and rather charges based on the overall voltage from the main lead.
• Fast Charge - most often this is a standard charge (not balanced) that finishes the charge at a slightly lower point than a standard or balanced charge. This saves some time and is good for when you need to get back in the air quickly. If you have the time, its better to use another option.
• Storage Charge - This charges the battery back up to a storage voltage, normally ~3.8v per cell. At this voltage, the battery can be safely stored for long periods of time. You can also use a storage charge to even out voltages on your batteries before parallel charging. Most chargers will both charge or discharge a battery back to the storage point.
• Discharge - If you absolutely can't fly your battery, you can discharge the battery via your charger. This slowly drains the battery.

Connecting the Battery

When charging multi cell batteries, you will need to connect both the main lead and the balance lead to your charger. You'll need the correct set of leads to connect your main lead to the charger. In our case the charger came with a + / - to deans cable, we added an adapter from deans to XT-60 and voila - compatible.

Be sure to carefully observe polarity here! Mixing your positive and negative terminals can be dangerous. Also be sure to unplug the battery from the connector before removing the bananna leads from the charger to avoid the possibility of shorting.

Also plug the balance lead into the charger. Make sure to connect to the correct port based on your battery (2-6s). The balance plug has two small notches which will help you correctly insert the plug. You should never have to force the balance lead in. If you feel resistance, stop and be sure you're plugging in to the correct port.

Setting Up the Charger

Using a battery charger to charge a single battery is a simple process once you understand the fundamentals. There are 3 things you need to know before you start:

• The type of charge you want to perform.
• The total capacity (mAh) of the battery.
• The number of cells in the battery.

Here is an example setup for a commonly used 1300mAh 4s (cell) FPV racing battery:

Most chargers use a similar set of menus. No matter the model you have, these steps still apply. First select the type of charge. In our case we will use a standard balance charge. Next set the amperage to charge at. You'll want to divide the milliamp hours (mAh) of your battery by 1000 to get a 1C charge rate. IE: 1300/1000 = 1.3 - we set the charger to 1.3A. Lastly select the number of cells in your battery - 4s.

Remember to place your batteries in a LiPo safe bag during charging.

What is Charging C Rate?

C rate or current rating is the number of times the rated capacity. For example if you have a 1000mAh battery charging at 1.0A - you're charging at 1C. If you charge that same battery at 2A, you're charging at 2C. Charging at high C rates will be faster, but can damage batteries. If your batteries are getting hot when charging at higher C rates, be careful. We recommend charging at 1C.

How to Parallel Charge LiPo Batteries

By using a parallel charging board, you can charge multiple batteries simultaneously using a single charger. This charging practice has many more complexities than standard charging. If you're going to be parallel charging, be sure to read along carefully.

In order to parallel charge 2 or more batteries, they must:

• Be the same cell count.
• Be at nearly similar resting voltages (within 0.1 of the total pack voltage).

As long as these two things are met, you are fine to charge those batteries together. The batteries can have different capacities (mAh). By connecting batteries in parallel, you're effectively showing your charger that you've connected a single large battery.

Checking Voltage

Before parallel charging you'll want to check the voltage of the cell(s) of your battery. You can do this with a small voltage checker or via your battery charger in 'battery meter' mode. Either way, you're looking for overall voltage (which can be found via the main lead) and voltage of each individual cell (found via the balance plug).

You're looking for the total voltage of the battery to fall within one tenth of a volt of each other. For example I would charge two batteries that were at 15.15v and 15.20v respectively. If they were 15.00v and 15.20v, I would not parallel charge them together.

Setting the Charge Rate

Again using our 1C charge recommendation, we are going to add the total mAh of all the connected batteries and divide by 1000. For example we will charge two 1300mAh 4s batteries that are both within the recommended voltage range of eachother. We would set the charge rate by adding 1300mAh x 2 (number of batteries) / 1000 = 2.6A.

Connecting Batteries to a Parallel Board

Once you're ready to charge, simply connect the batteries as you would to your charger. The main leads go in the center of the board. The balance connectors go in the appropriate slot to the outside. Most boards include an additional connector on the bottom allowing you to chain multiple parallel boards together. This doesn't mean you can run out and  charge 24 batteries at once. The limiting factor is the amperage output of your battery charger.

Charging Single Cell Batteries

This is a common question for pilots who are flying micro FPV quadcopters like the Tiny Whoop. These small drones use single cell batteries and often include only a single port USB charger. It is possible to charge single cell batteries using a full featured digital charger. You'll be using the standard charge mode, not balanced - only one cell means there is no need to balance.

To connect the micro JST connector, you'll need a special lead with the female connector type. You can also use a tiny parallel charging board to charge multiple batteries at once. This is our recommended route as with flight times as low as 2-3 minutes per battery, you'll want to charge multiple batteries at a time.

In this example we are charging six 210mAh Tiny Whoop batteries using a parallel board. We set the charge type to standard, set the cell count to 1S 3.7v, and charge at 1.2A. This equates to just slightly under a 1C charge as 6 x 210mAh = 1260mAh / 1000 = 1.26A.

Safe Storage & Use

One of the most important accessories you'll need to buy is a LiPo safe bag. These bags are used when charging and storing your batteries. They are designed to contain the smoke and flame that may occur from a damaged or shorted battery. It is super important to purchase and use one of these bags.

When to Discharge a Battery

Discharging, or simply using the power within the battery is important to monitor closely. You can discharge batteries in two ways. First by simply using the battery (our preferred method) and second by discharging via your battery charger. Do not leave LiPo batteries charged for long periods of time. Batteries that are stored more than a 2-3 days should discharged. As we discussed above, each cell has a 3.7 resting voltage. If the voltage in a cell drops below 3 volts, the battery will no longer charge.

Travelling with LiPo Batteries

The TSA allows passengers to carry LiPo batteries onto airplanes. You must take some precautions when travelling with your batteries. The following checklist will help you pack for your next trip:

• Do not place LiPo batteries in your checked baggage.
• You should tape the terminals of your batteries and place them in a LiPo safe bag.
• Never travel with damaged batteries.
• Do not pack them near anything sharp.
• Discharge your batteries to a storage level before travel.

Browse LiPo battery options in our product database.