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LiPo battery tutorial: The concise beginner guide

Written by V Kadamatt

Do you want to avoid a battery explosion? Want to learn what the ratings and readings mean and how to increase the life of your LiPo batteries? If so, this LiPo battery tutorial is for you!

This is a vast subject but we’ve distilled the most important bits you must know as a beginner UAV/Drone/RC pilot.

First, you will learn about the LiPo battery (i.e what the ratings and readings mean).

Then, you will learn how to select the correct battery for your model and how to charge, balance, store, revive and dispose them.

Read on!

LiPo care infographic

LiPo battery care

LiPo batteries explained

LiPo battery tutorial: LiPos ExplainedWhy LiPos?

Lithium Polymer (LiPo) batteries are the most popular source of energy for powering up RC crafts (or ‘Drones’) and vehicles today. Without going too much into detail, the main reason for this is because they are rechargeable and typically have large capacities.

They come in varieties that have discharge rates large enough to power even some of the most demanding RC crafts. This makes them the preferred choice over other options such as the Nickel Cadmium (NiCd) battery. This is also the primary reason they can replace an actual fuel source.

LiPo Guide : What are the wires/connectors and what do all the ratings mean?

A typical LiPo battery, regardless of cell number should have two main connectors – one being the main connector (also the thicker one) and the other being the balance connector.

The main connector can be used for charging the battery quickly at the cost of cell voltage balance in multi-cell batteries. It is also the connector that is directly plugged to your actual RC electronics. Typically, the red wire connecting to the connector is positive while the black wire is negative.

The balance connector is the one with the thinner wires. This connector is plugged in to a battery charger to get a balance charge, keeping the voltages of the cells in the battery near equal. More about charging is covered in the how to charge section.

For beginners, it can be really daunting to see all the different numbers printed on a LiPo battery. Worry not, the readings are actually simpler than it seems. Really, it boils down to five different things – Voltage, cell count, capacity, discharge rate and charge rate.

Voltage

As you may already know, voltage is the direct measure of the electromotive force (or potential difference) within a cell. What does that mean for you and your RC craft? Well it is what determines how fast the motors on your RC craft spins.

Brushless motors come with a kV rating. For every volt you apply on such a motor, it will spin at that particular RPM (rotations per minute). For example, if you apply 1 Volt on a 1000 kV motor, it would spin at 1000 RPM. 2 Volts would mean a 2000 RPM spin.

Note that the voltage reading on the battery is usually the total voltage from all the cells in the battery pack. Each cell within a LiPo pack has a nominal voltage of 3.7 V. However, when a cell is fully charged, it can go up to 4.2 V. This is not ideal for longevity, but more on that later.

Cell Count (S rating)

The ‘S’ (short for series) is the total number of cells that are in your battery pack. A 1S battery is a single celled battery, while a 3S battery has 3 cells in it (connected in series). You may rarely come across with batteries that also have a ‘P’ rating along with the S rating.

This is just a reading of the number of batteries that are connected in parallel. For example, a 3S2P battery has 3 cells connected in series and 2 cells connected in parallel.

Capacity

The capacity is the amount of ‘fuel’ your battery has in reserve. The larger the capacity, the longer the run time before it is time to recharge again. This is measured in milliamp hours (mAh) load (1 amps (A) = 1000 mAh). It actually is a time measurement than the actual amount of current in it.

For example, a 1000 mAh (or 1 A) battery would be completely discharged in 1 hour if you put a continuous draw of 1 A (1000 mAh) current on it.

A 5000 mAh (or 5A) battery would discharge completely in 5 hours if you put that same load on it. If you double the load to 2A (2000 mAh), it would discharge in 2.5 hours.

Obviously what this means for you is that the higher the capacity for your battery, the longer flight times you can expect. There is an important caveat here however – batteries tend to get really large and heavy at larger capacities and so you cannot simply scale this indefinitely.

Discharge rate

Discharge rate (‘C’ rating) is directly tied to the capacity reading. This is the measure of how much of the capacity of the battery can be pulled off at a time.

To give you a concrete example, if you pick a battery with a capacity of 1000 (mAh) and a 10 C discharge rating, you could potentially pull 1000 * 10 = 10000 mAh (10 A) power off that battery continuously, without damaging it.

Now of course, at a 10A current draw you cannot expect that battery to last for an hour. We already know that at a 1A draw it would last an hour (or 60 minutes). At a 10A draw it would last 60 minutes/10 = 10 minutes. This is a reasonable flight time for a lot of RC crafts, especially multirotors.

Some battery packs show a ‘burst’ C rating. This is the capacity for discharge at a higher rating than usual for short periods of time. This is useful in situations like steeply climbing altitudes or performing flight acrobatics.

Charge rate

The charge (‘C’ rating) is the rate at which you can safely charge the battery. For example a 1C charge rate on a 1000 mAh battery allows you to charge your battery at 1000 mAh. Therefore, it would take about an hour to charge it!

A 5C charge rate on a 1000 mAh battery would allow you to charge it completely in 60 minutes/5 = 12 minutes.

If this measurement is not explicitly given in your battery pack, stay safe and charge at 1C.

How to select a LiPo battery: Some important factors to consider

How to select a LiPo batteryNow that we have LiPo batteries explained, how do we go about selecting one to suit our needs? What are some of the most important factors that we must consider? Let us arm our new found knowledge!

Go for the highest C rating possible

If budget permits, go for the highest C rating possible on any given capacity. If you get too frugal here, you could damage your motors and ESCs! Not to mention you would be completely limited in your ability to do all the cool moves with your RC craft!

When you are out LiPo shopping in your local hobby store, it is better to pick one solid, highly dischargeable battery than 2 or 3 batteries with low C rating.

Make sure it doesn’t get too heavy

Weight is an important factor to consider when selecting your LiPo batteries. Even if you get a battery with the largest capacity on the planet, it may not give you the flight times you’d expect.

Remember that the heavier the craft gets, the harder it is on your motors and propellers. This means more power drawn and that defeats the purpose of going for a larger battery in the first place! And if you go too heavy, your craft may not fly at all!

Voltage!

When you pick your LiPo, make sure it meets the voltage requirements of your motors! For example, if your motors require 10 volts, make sure your batteries have a reading of at least 10 volts!

This means that the amount of required cells in your battery (The ‘S’ rating) would vary from motor to motor!

Like discharge rate, if you go too low, it will damage your motors!

How to charge a LiPo battery

How to charge a LiPo batteryProperly charging your LiPo battery is of paramount importance not only for longevity, but also for safety. The MOST important thing to remember is to onlycharge your LiPo using a LiPo battery charger! Charging it with any other charger can cause some serious damage.

Most LiPo chargers available in the market today comes with an inbuilt balancing capability that will level the voltages in the cells in your battery. If possible, get your hands on one of these and do a balance charge whenever possible. This may take longer, but it’ll help with longevity!

It is also important to remember to pick a charger that can accommodate the appropriate cell count (S rating) for your LiPo. For example, never charge a 3S battery using a charger meant for a 2S battery!

Charging rate

We’ve already covered what a charge rate (C) is. Most batteries come with a charge rate of 1C and this is the safest to go for, if you are unsure of your battery’s capabilities.

Even if the battery comes with a potential for higher charge rate, it is recommended that you charge it at 1C to minimize damage and to ensure maximum longevity, especially if you aren’t in a hurry to head out with your RC craft.

Regardless of the specifications on your battery, constantly charging it over 1C will definitely have an impact on its overall life. Patience vs life? You decide!

Avoid overly charging or discharging

Like we discussed earlier on in this post, a LiPo battery can go up to 4.2V when fully charged with a LiPo battery charger. This is the absolute maximum you must charge your battery to. Anything above this and you significantly reduce the life expectancy of your battery!

4.2V is still not ideal if you want maximum longevity off your battery. For this, charging your battery till it hits around 90% charge rate is ideal. This means getting it up to about 4.15 to 4.17 V range. Of course, this comes with a cost of reduced one time flight time!

Over charging is not the only way you can damage or reduce the life expectancy of your batteries. The absolute minimum you should discharge your battery to is to about 3 – 3.2V. Beyond that, you again run the risk of damaging the battery and/or reducing its life expectancy.

This is an important thing to remember when you head out to fly your RC craft. Never fly till your battery charge hits rock bottom if you want longevity. Land when your battery charge goes down to about 20% instead of an absolute 0. This will do more than just protect your craft from a crash landing!

Other safety considerations

If you do not expend some thought energy to actually care for safety of your LiPo battery, you open up the possibility for causing some serious damage to yourself and your surroundings. This cannot be stressed enough. Life is unpredictable enough, so do not overlook this!

The first thing to remember is to absolutely not go out for a party if your LiPos are charging unless you want to witness your house burnt down when you return. Sure, the odds maybe slim but why take chances?

Always make sure that you are in proximity of a charging LiPo battery because if and when things go wrong, you must be there to react to it! Make sure that charging your LiPos is done in isolation, away from easily flammable objects and material in your household.

In most cases, LiPos catch on fire if they are charged or discharged at a high rate immediately after a flight. It is important to remember that the battery get heated up during the flight. It is hence wise to let it cool off before you charge or discharge it.

If you can get your hands on a LiPo bag, please go ahead and do so. It is essentially a fire resistant container that can contain a LiPo battery burn if things head south. Do note that most of these bags tend to be of low quality so it is important to pick one that has good reviews!

How to balance a LiPo battery

How to balance a LiPo batteryWhat is balancing and why you need to do it

What exactly is the process of battery balancing? Well, we’ve already covered what a cell count is. In batteries with multiple cells, balancing is simply the process of making the voltages of the cells in the battery pack equivalent.

Why do we need to do this and what would happen if the cells go unbalanced? For example, in a 2S battery that is charged, if one of the cells has a voltage of 4.1V and the other has a voltage of 4.2V, it is the unbalanced.

To put it simply, unbalanced cells in a LiPo battery significantly reduces its life expectancy. Not only this, it will also give you lower flight times than usual. Balancing is very easy to do, so why throw away the battery for nothing?

How to check if your battery is balanced

The first obvious thing you’ll need to do is to check if the cells in your LiPo battery are actually unbalanced. If you can, go ahead and buy a battery meter. Most of these battery meters can do more than just check the voltages of your battery.

Some of them can act as a discharger, check the capacity of the battery (in case you tear the front sticker of your battery) and also check the internal resistance of your battery.

To ensure that you get the most out of your batteries, it is necessary to regularly check the voltages of your battery and see if it is balanced. Battery meters are in my opinion a great investment!

Using a battery meter is usually as simple as plugging in the balance plug into the meter. From then on, it is easy to check the individual voltages of the cells to check if it is balanced or not. If you want more about balancing, here is a decent article on it.

How to balance a LiPo battery

Okay, now onto actual balancing of the battery. It is easier than you think it is. All you need is a charger capable of doing a balance charge, which is basically most LiPo chargers these days.

It is as simple as plugging in the balance connector (from the smaller wire) into the balance charger, setting up the appropriate voltage, capacity and settings on your balance charger and voila! You are done! Here is a nice little video of this process. I love this guy!

How to store a LiPo battery

How to store a LiPo batteryHow to discharge a LiPo battery for storage and why

The very first thing you need to know about LiPo storage is that you must neverstore a LiPo battery fully charged. Why? Because the cells in the batteries function from chemical reactions.

Keeping it stored fully charged for long periods of time will degrade the cell from these increased chemical reactions, causing it to puff and/or have reduced efficiency at the bare minimum when you use it again.

On the flipside, discharging your cell below 3V will damage our cell as well. Storing it at anything below 3.5V per cell voltage will increase the chances that your battery loses its efficiency and life expectancy.

What is the ideal voltage then? Well, the very ideal voltage range for storage is 3.7V per cell. This is about 50% of the charge. Anything from 40% charge to 60 % charge should work well, however.

Discharging a LiPo battery for storage is pretty easy, much like charging it. All you need to do is to plug in your battery into a balance charger or a multipurpose battery meter and set it to discharge for storage. If your charger doesn’t have the automatic function, just discharge all the cells till it reaches close to 3.7V.

Where to store LiPo batteries?

Now that we have voltages out of the way, where do you actually store the batteries? The ideal place for storage is in a cool room with no inflammable or magnetic objects around it.

Storing it in a really hot place can entice a chemical reaction and damage the cells. If you have an ammo box or a LiPo bag, store the battery in it.

Storing LiPo batteries in a fridge is not unheard of. If you go this route, make sure you put it in a LiPo bag or an ammo box before putting it in the fridge!

I DO NOT recommend doing this because if not done correctly, like emptying the air from the container (typically a plastic bag), it can cause condensation and therefore damage your batteries. I’d rather just store them in a relatively cool place.

How to revive a LiPo battery

How to revive a LiPo battery
So what if you made the mistake of over discharging your LiPo battery cells (below 3V or even 3.2V in some cases) and your charger refuses to charge the battery? For maximum safety, you dispose it. Do not attempt to revive a dead LiPo battery if you aren’t sure what you are doing!

I’d only recommend attempting to revive it if you are absolutely positive that it is not supposed to be dead (no puffing or deforming of the battery for example) and if you have taken necessary safety precautions. You do not want a LiPo fire!

Spending a couple of bucks to buy a new battery is always better than risking your safety especially if your battery is old. That being said is recovery possible? Absolutely! It is not guaranteed, however.

Also, do not expect a recovered battery to be like a brand new one. 9 times out of 10, it will be weaker than ever before and give you much less flight times. All the more reason to get a new battery pack!

Here are a couple of ways you can go about restoring a LiPo battery (Note that I DO NOT recommend any of these methods. Do it at your own risk):

Using a Nickel Metal Hydride battery mode on the charger

Connect your dead LiPo battery to the charger and use the Nickel Metal Hydride setting. Set it to the lowest charge rate and charge the battery for about 10 – 15 minutes. Now, plug in the balance plug into the charger and change the setting to LiPo and check the individual voltages of the cells.

If the LiPo cells have a voltage higher than 3V, then disconnect the main charger and let the charger do a full balance charge to 4.2V. This procedure should recover your dead LiPo battery and get it to functioning again.

Connecting the dead battery to a live one for a minute

This is a much riskier method and the chance for short circuit and a LiPo fire is higher. Nevertheless, this method may come in handy if you do not have a smart charger. You must have another LiPo with the same amount of cells, however.

Connect the dead LiPo to a live one using external wires. A jumper wire with protection should do, but ideally get a thicker wire. Make sure you connect the positive end of the dead battery to the positive end of the still working one and the negative end to the negative one.

Leave the batteries connected for about a minute. Check the voltage of the dead LiPo battery and if everything went well, you should now see a positive reading. If not, I wouldn’t try repeating the procedure.

Safety considerations

Put the battery in a LiPo bag in to contain a LiPo fire if things go wrong during either of the recovery procedure. Also remember to keep a fire extinguisher nearby and absolutely positively DO NOT WALK AWAY FROM THE battery when you have kept it for a recovery.

Do the procedure on a concrete floor and away from any other object. There is a lot of risk involved so please do not overlook these simple safety measures!

How long do LiPo batteries last? When and how do you dispose it?

How to dispose a LiPo batteryThe lifeline of your LiPo batteries will depend on how well you take care of it. If all is good, it should last about 300 cycles. Constantly exposing the cells to high temperatures and not regularly balancing it can exponentially reduce how long it will last.

To squeeze out maximum lifetime out of the LiPos before you throw it away, you should take care of it properly – Keep the cells balanced, make sure you do not charge it over 80% (about 4.1V) and do not discharge the cells below 3.4V.

How to tell if a LiPo battery is bad

You can tell if a LiPo battery is bad and needs to be disposed by the following:

  1. It is best to consider a LiPo dead if you attempted recovering the battery once in the revival techniques we covered above. Do not try to recharge a dead battery too much for safety reasons. Remember – No LiPo fire!
  2. If you managed to successfully recover the battery and find that the discharge rate is too pathetic for any practical use, time to throw it away.
  3. If the battery cells discharges too unequally every time, time to throw it away. For example, after flights session on a fully charged 3S battery, if the battery cells reads something like 3.3, 3.3 and 3.5, your battery is bad.
  4. A sure way to tell if your LiPo battery has to be disposed is if your LiPo battery gets puffed. Never keep using a puffed battery even if it works. It is a risky endeavour and you risk fire/explosion.

How to dispose of a LiPo battery

The first thing you want to check is if the battery pack is physically damaged or not. If so, you should go right ahead and submerge the battery in salt water. If could discharge it first, but be careful and let it discharge at a very low rate (below 1 C).

If the pack is not physically damaged (puffing, for example), you should first discharge the cells of the battery. DO NOT discharge when it is hot, wait for it to cool down if it is hot. Make sure you put the LiPo in a fire proof container like an ammo box during the discharge.

If you do not own an ammo box, fill up a thick plastic container with sand in it and submerge the LiPo in the sand during the discharge. Connect the LiPo to a discharger and set it to the lowest possible voltage and let it drain completely.

For safety, discharge it in 1C. To discharge, you can connect the battery to a mini light bulb, a mini motor or a power resistor and let the voltage of the pack go all the way down to 1V per cell. Note that you may not be able to measure the voltage using a battery meter or a smart charger at low voltages so you may have to use a volt meter or a multimeter.

After you have done that, fill up at least a gallon of salt water in a plastic container. I’d recommend adding around half a cup of salt to the water. Submerge the LiPo battery inside the container and leave it be for 2 weeks. IMPORTANT – Keep the container with the submerged battery away from anything that is flammable, pets and children. It is also imperative that you close the lid of the container.

After the 2 weeks of submersion is done, you can now safely dispose it away in the trash.

If you do not want to go through all the steps, the absolute best thing you can do is to take it to your local waste disposal centre or to a hobby shop. They will typically dispose them properly. DO NOT however, throw your LiPos in the garbage can without properly discharging it.

In closing

If you are a UAV or RC owner or enthusiast, it is imperative that you understand at least the basics of LiPos to not only be informed and responsible in terms of properly taking care, storing and disposing them but to thoroughly enjoy operating the machine that the battery powers.

A properly maintained, healthy LiPo battery is not only LiPo fire and healthy proof, but also stronger in terms of providing the necessary power you require.

That’s all folks! I hope this article helps you. If you have any questions, comments or suggestions, please drop them below! Also, to make things easy for you, we have put together a weekly LiPo care checklist!

Download the free checklist (pdf):

LiPo care checklist

 

 

About the author

V Kadamatt

Artificial Intelligence , UAV and RC enthusiast. Software professional, part time philosopher and star gazer.
I also love physics, mathematics, economics, psychology, fantasy, Sci-Fi and futurology.

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