In this article we will look into how to choose LIPO battery charger, and hopefully it should give you some idea in picking the best LiPo charger for multicopters.
When buying a LiPo battery charger, it would be easier if you could just walk into a hobby shop, and ask the staff what charger you should get. However if you are getting it online you are pretty much on your own. Therefore researching beforehand, knowing what you need and what options available are very important.
Choosing LiPo Charger for Quadcopter
We have talked about how to choose the best LiPo Battery for your mini quad build. We have covered most areas in building and flying quadcopters, but LiPo charger is rarely mentioned. In this post, we will go through some of key factors in selecting a good LiPo battery charger, for your quadcopter and other multirotors.
These are the important consideration when choosing the best LiPo charger.
- Technical Specification of a LiPo charger
- Extra Features
- Choosing Power Supply for Lipo battery charger
- Quality and Cost
Here are some lipo charger recommendation from our multirotor group: top 5 best LiPo chargers for mini quad. However we urge you read through this guide to learn about the basics and specifications before deciding.
There are non-programmable charger which are “plug and charge”. You just need to plug your battery into these charger, and it will start charging, no input from the user is needed. These might seem simple, and economical too, but they are very slow in charging, and you can’t change any of the settings and options.
High quality chargers nowadays are almost all computerized and programmable. A programmable charger allows you to set all sorts of parameters, such as charging current, type of batteries, charging period etc. They show you the battery condition such as what the voltages is each cell, how much current has been charged into them and so on. It basically manages the charging for you in the way you want, ensuring the batteries are charged safely and accurately.
Some of the programmable chargers also do clever things including, adjusting charging current depending on charger temperature, auto-detecting battery cell counts and battery voltage level. You can even discharge your battery for storage with some programmable chargers.
LiPo Battery Cell Count Supports
Some charge can charge Lipo battery up to 4S, some up to 6S or even higher. It all depends on what you need, now and in the future. For most people I think 6S support is good to have and should more than enough for now. If you fly micro quads running 1S batteries, you might also make sure the charger can charge 1S too (although you could make a cable that charge 4x1S batteries as 1 4S battery like this)
The charge current is limited by two factors:
- How much your LiPo Battery CAN TAKE
- How much your charger CAN PROVIDE
For safety, LiPo batteries are often recommended to be charged at no more than 1C. Although some expensive LiPo batteries are advertised to be fast charging capable, which can be charged at 2C or even higher. If your batteries aren’t very good, and you charge too fast, they could overheat.
To charge at 1C means you are charging “at the rate of its capacity”. For example, if you have a 3S 2000mAh LiPo battery, the charge current would be 1C x 2000mAh = 2000mA = 2A; To charge at 2C, the charge current would be double, at 2 x 2000mA = 4A.
Every charger has a power rating, and a maximum charging current rating. The maximum charging current a charger can provide is limited by these ratings, whichever limit is reached first.
How does power rating affect current? Basically you take power and divide it by voltage, you get current. (P = V * I)
For example, for a 100W charger, to charge a 4S LiPo, the voltage would be 16.8V when fully charged, So you can calculate the max charge current to be 100W/16.8V = 5.9A.
Note that this current actually varies as voltage changes through out the charging cycle. When the battery is empty at 14V, the charger can actually charge faster at 100W/14V = 7.1A. The current gradually decreases with increasing the battery voltage and eventually down to 5.9A when the battery is nearly fully charged.
Charger Power Output
LiPo Charger Power is measured in Watt which is calculated by multiplying voltage (Volts) and current (Amps). If your charger does not meet the power requirement, you might find it charge your battery at a lower current.
Calculate the Required Power
To work out how much power you need in a charger, you can simply multiply the charging voltage and current. For example, to charge a 3S 2000mAh LiPo at 12.6V at 1C (2A), you will need a charger that are rated for 25.2 watts (= 12.6V x 2A) or higher. So it’s clear that if you want to charge at 2C (4A), you will need double of the power to 50.4W.
Note that when dealing with different cell count LiPo, the max charge current also varies, but it should not exceed the max charge rate of your LiPo charger. For example for a 50W charger that has a rated 5A max charge current, you will find the actual max charge current for 3S battery to be only around 4A (= 50W / 12.6V). But for a 2S battery, the calculated result is now nearly 6A (= 50W / 7.4V). But you wouldn’t be able to charge at 6A because the charger is rated for max 5A .
This is so far only an estimation, there is also efficiency loss so you definitely need higher wattage than the number from our calculation. It’s safe to assume a power loss of around 20%, so if you are looking at 50W, a 60W charge would be a good choice (50*120%).
You need Higher Power for Parallel Charging
Once you start charging higher voltage batteries or start doing parallel charging, you would need a more powerful charger. Let’s calculate how much power we need for parallel charging:
For example to charge six 3S 2200mAh LiPo batteries at 1C at the same time, the max charge current would be 13.2A (= 1C x 2200mA x 6). And the power requirement would be 199.6W (= 13.2A * 12.6V * 120%). In this case, I will get a charger that is rated for 200W or more, with a max charge current of 14A or higher. You can certainly use a lower power charger in this situation, the only downside is the charging would take longer as it can’t deliver that much power and current.
The Types of Batteries Supported
For mini quad’s all we need is LiPo Support, it’s also good to have HVLi support. It would be a bonus to have NIMH support too which is useful to rescue over-discharged LiPo that cannot be recognised by the charger. Some chargers might support other types of batteries too including NiCad and PB which might not be that useful to people who only fly multirotors.
Charger might or might not have the following charge modes, here explains what they do:
- balance charge – this is the safest and most used charging mode on the charger. Both the main lead and balance lead are plugged into the charger, so the voltage of each cell is monitored and can be made sure balanced during and after charging
- fast charge – charging is faster because it doesn’t monitor and balance the individual cell voltage; It only looks at the overall voltage and there is a risk of overcharging one or multiple cells in the battery. We don’t recommend this mode unless you know what you are doing
- discharge – this mode brings down the voltage of a lipo battery to as low as the charger allows (some might be 3V, some might be 3.3V, it depends on the charger and settings)
- storage charge – puts your lipo battery cell voltage to 3.8V, which is the voltage suitable for long-term storage
A decent charger should at least have “Balance Charge Mode”, “Discharge Mode”, and “Storage Charge”.
Most low power chargers are single channel chargers. Multiple-channel charger are very powerful, basically each channel can be used as a smaller charger. For example with a 4-channel charger, you can able to charge 4 completely different batteries at the same time, regardless capacity, votlage level, cell count… almost like you are charging them on a separate charger.
They are great as you won’t need a parallel board to charger multiple batteries, and you can set different settings for each channel such as charge current which makes it really handy.
You probably don’t need all of the following extra features, but they are good to have. The more features it has, the more expensive charger it’s going to be.
Some basic charger features
- Backlight LCD display.
- Shows voltages of each cell when charging.
- Precise voltage reading of 0.01 – 0.02 volts.
Some Safety features
- Cell count confirmation protection before charging.
- Over and Under voltage protection.
- Temperature detection and limit setting for overheat protection.
- Time out feature (stop charging after certain period of time).
- Warning buzzer.
And more advance LiPo charger features
- Support many rechargeable battery types.
- Measuring Internal Resistance of each cell and the entire battery.
- Profile programming for LiPo of different capacity and cell count, so you don’t have to set up parameters like charge current etc everytime you charge them.
- Computer connection and GUI. Some high end charger allows you to connect your charger up to your PC, so you can see realtime data like charging current, voltage level of each cell, time remaining etc. On some of them you can even update charger firmware too..
Choosing Power Supply for Lipo battery charger
Power Supply is also known as PSU. If you are buying a charger with built-in PSU, then you can skip this section.
Chargers without a built-in power supply are usually cheaper and lighter, however that means you will have to buy one separately. A charger dedicated power supply can cost quite a lot, sometimes are as expensive as the charger itself. There are other cheaper alternatives such as computer/server PSU’s which you might need to do a bit of DIY.
The charger specification should tell you what the input voltage (range) should be, and your power supply should have an output voltage that meets that requirement. The power supply also need to provide enough power for the charger. The power supply power is calculated by multiplying output current and output voltage.
So if you have a 100W charger, you would need a power supply rated at least 100W. If you buy a bigger power supply, there’s not much advantage except for future-proofing. With a under-powered power supply, you could overload your power supply and cause overheat issue and eventually burns out.
Here are some recommendations:
Charger Quality and Cost
A LiPo charger should be treated as a long term investment when you start out in RC hobby, just like your radio transmitter. So expect to spend fair amount of money on the quality chargers.
The most expensive charger is not necessary the best, but a good quality charger comes with reasonable price. My advice is, don’t look at the how much it is before you figure out what you actually need. List your requirements on a piece of paper, and find the chargers that you are happy with. If you don’t need the “fancy features”, then don’t add it to your list.
If you don’t find anything suitable locally then try shopping abroad, It offers you more options with lower prices. Most of the chargers you find will probably be made in China or other countries. It’s a stereotype that China always make bad products, not necessary true. In fact most RC products are made in China these days, including some really top notch brand names.
Picking a LiPo battery charger is just like any other quadcopter parts, it’s quality versus price. But unless you actually try in, you won’t know how good or how bad it is. So read some other guides on how to choose a LiPo battery charger, ask on forums, do your research, and make sure you have a good understanding of LiPo charging before making your decision. This article is based on my personal experience, if there is any error or missing info please let me know.
Happy flying and charging!
- 2015 Feb – Article created
- 2017 Jun – Added charger’s modes