li-ion battery charging

by:CTECHi     2020-02-01
Lithium-based battery is a multi-functional energy storage method;
They have the highest energy density and specific energy (
360 to 900 kilojoules/kg)
In a rechargeable battery
The downside is that unlike capacitors or other types of batteries, they cannot be charged through regular power supplies.
They need to be charged to a specific voltage and a limited current, otherwise they will become potential Molotov.
This is not a joke, it can be very dangerous to store such high energy in a small and usually tightly packed device.
But because the battery voltage is relatively high, they are very useful in electronic products;
High energy density;
Their shape, size and type of capacity as well as charging/discharging efficiency.
That\'s why they consume electronic products in almost all.
Because they are the best choice for small and medium-sized portable devices, they are popular in the DIY community.
But if you don\'t want to buy specific chargers, charging is still a common problem when using them.
Through this instruction you will learn how to make a suitable li-
Ion battery charger with widely available components and parts.
More importantly, you will learn how it works.
Jump to Step 6 if you want to skip the theory and actually build the charger.
There are many different types of lithium-based batteries, but they are only different in the materials and structures used.
Scientists prefer to name batteries with chemical names and materials used, and these terms can be confusing unless you are a chemist.
The table above provides clear information by listing the full names, chemical definitions, abbreviations, and short forms of these batteries.
Different types of batteries have different features and limitations, for more details, I suggest you visit this page.
The good news is that most of the batteries are charged in the same way, at least the common ones you will usually find and/or use for the batteries --Power Project.
First of all, you need to know what \"C-
Because it is the basis for battery use.
Most batteries are marked with nominal capacity to amp-hour (Ah)or in milliamp-hour (mAh).
This is basically the discharge current they can supply for an hour before they are completely exhausted.
For example, you have a large battery marked 2400 mAh or 2.
4Ah, it means that you can push 2.
4A through your circuit, discharge in an hour
For a long time.
This will be the 1C discharge rate, which is discharged at the rated capacity current.
If your battery supplies 1200 mA to the circuit, it will be 0.
The 5C discharge rate should last for two hours.
Some batteries allow a higher discharge rate than 1C, if you can discharge at 4. 8A (2C)
It will last 30 minutes.
Some of the batteries used in the RC system allow a very high discharge rate, such as 10 or 20 °c, but this battery is usually designed to fail instead of having your plane cut off in the middle
So they\'re not the safest.
When charging, it is basically the same, charging 2400 of the battery with a maximum current of 1200 mA will be 0. 5C charge rate.
For safety reasons, most batteries should be charged between 0. 5C and 0. 7C. Most lithium-
The ion battery is charged to 4.
2 v per battery, higher voltage can increase the capacity but will reduce the service life.
The lower battery charge cycle can be at the expense of a shorter run time. (
See the third picture)
The charging cycle includes two main stages;
But some chargers skip or add more stages. (See graphs 1&2)
Usually only Phase 2 and Phase 3 are used, and it may take 2 to 4 hours to fully charge depending on the charging rate. Li-
Ions do not need to be as charged as lead acid and do not want to do so.
In fact, it is better not to fully charge because the high voltage will put pressure on the battery.
Choosing a lower voltage threshold, or completely eliminating the saturated charge, can extend the battery life, but this reduces the running time.
As the consumer market promotes the maximum running time, these chargers pursue the maximum capacity rather than extending their service life.
For more information, you can access this page.
I started using op amps about a year ago and I decided to design a suitable li-
Learn to use an ion battery charger.
I learned a lot about op-
In the process of designing this circuit, I want to share it so that people can make their own Chargers instead of buying them.
The circuit uses the popular LM324 op-
Create an amplifier for current and voltage limiting power supplies.
In this case, the current can be adjusted with a potentiometer of about 160 to 1600 mA, which enables it to charge a battery with a wide capacity range.
The Volta limit is 4.
2 v so you won\'t damage your battery.
It has a charging indicator LED that lights up when the battery is charged and turns off when it is finished.
I designed this circuit so it uses a wide range of available and cheap
So anyone can build it.
Almost all general operations
The amplifier can be used, no rail-to-rail operation is required, no high frequency or high precision is required.
The Tip122 transistor can be changed to any pin
Compatible transistors with minimum DC current gain (Hfe)
Over 100 and maximum collection current (Ic)over 2A.
The design of the circuit makes it easy for anyone with basic welding skills to build it.
The entire battery charger is powered by a 12 v 2A charger, but since the LM324 is not a rail-to-rail op-
Amplifier, I need a second voltage rail to allow the operation
Amp sensing voltage near GND (
Small voltage of small current)
When the Darlington transistors should not be turned on, the output voltage is low enough not to turn them on.
If you look at the general schematic of the previous step, you can see that the transistor that controls the current and voltage at both ends of the battery is connected to the voltage rail, not to the ground.
This is because the output voltage of the LM324 cannot reach the negative supply voltage, so it can only be around 1. 5-2v over it.
Under this voltage, the Darlington transistor will not be able to be turned off, nor will it be able to properly limit the voltage and current.
That\'s why I used one of the four op\'s. amps (IC1a)
Create a virtual 2 with a transistor.
The 5 v rail on the GND absorbs the current flowing through the charger part of the circuit.
R2 and R3 are the voltage divider with an output voltage of about 2.
5 v depends on resistance tolerance, op-
The Amp drives the transistor in a way independent of current 2.
5 v will always touch it. The four op-
The amps and LED indicators are powered directly from the 12 v power supply, but the rest of the circuit is powered by 9. 5v;
Between 12 v and 2. 5v rails.
If you use this design but you want to make it more efficient you can use the rail
Amplifier and lower voltage power supply, so you do not need to generate additional track waste power in additional transistors.
The power supply LED indicates when the charger is turned on and C2 smoothing the voltage of the charger.
This is an important part of the charger, which is the key to limiting the current and voltage of the battery.
In this case, the charging current can be selected with a 10 k potentiometer, but the limit voltage will be a fixed 4.
2 v reference, no matter how the supply voltage changes. (
You can see that in the general schematic, the value of potentiometer and R8 and R9 is an order of magnitude higher, because my only pot is a pot of 100 K, but the recommended value is 10 k, for R8 & 9, the value in the diagram above)The op-
Amplifier on the left (IC1c)
Note that the current is limited to the maximum setting with a potentiometer.
Since the sensing resistor is 1 ohm, the voltage passing through it will be the same as the current flowing through it.
At the top of the 1 k resistor there is a potentiometer with a drop of 160 mV on the resistor, so the minimum output voltage of the potentiometer is 0.
16 v, in this case, the circuit will limit the maximum current by 160 mA, which is ideal for charging the 300 mAh battery.
The voltage drop at both ends of the potentiometer is about 1.
Therefore, the maximum current limit will be slightly higher than 1. 6A.
Adjust the potentiometer and you can get any voltage output between 0. 16 to 1.
6 v, which means the maximum current limit between 160 and 1600 mA. The op-
The Amp will drive the transistor so that the voltage on the sensing resistor is the same as the potentiometer output.
Thank you two.
5 v rail, op-
The Amp will be able to output a voltage low enough to turn off the transistor almost and set a low current limit.
At the end of the constant current phase, the battery voltage is close to 4.
The 2 v limit, beyond which the battery will be damaged, at which point the voltage limit part of the circuit starts to start and the constant voltage phase begins. The 4.
The 7 v Zener diode produces 4 together with the R10 & 11 divider.
2 v reference below VCC (~12v).
When the voltage at both ends of the battery reaches 4.
2 v, the second op-amp (IC1d)
Start pumping the voltage into the reverse input of the first op-
Amp, which makes it possible to reduce the output voltage to the transistor so that the current of the battery starts to drop to hold 4. 2v across it.
As the battery charges and the internal resistance increases, it takes less current to keep 4.
2 v, so the current will drop slowly.
When the current flowing through the battery is less than 3-
With a nominal capacity of 10%, the battery is considered to be 100% charged.
Depending on the charging rate, it may take 2 to 4 hours for the battery to fully charge (
I suggest keeping it between 0. 5 and 0. 7C).
When the current flowing into the battery is less than 3-
10% of the nominal capacity, 100% of the battery charge, when this happens, the circuit above will tell us. The fourth op-amp (IC1b)
Used as a comparator; at the non-
Reverse the input, which passes the voltage through the sensing resistor (over the 2. 5v rail)
This will drop during the constant voltage or saturated charging phase and compare it to a fraction of the voltage set by the potentiometer.
R15 and 16 voltage divider outputs 9% of the set voltage and will refer to the input op-amp.
When the voltage at both ends of the induction resistor (
Same as the current flowing through the battery)
Lower than the reference voltage set by the voltage divider, in-
Bigger than in, so op-
The amplifier output drops to GND and turns the LED off.
With this configuration, the LED turns on when charging, and the LED turns off when the battery is fully charged.
If you want to turn it on at the end of the charge, just swap the op-amp input pins.
Now that we have finished the theory, let\'s actually build the charger!
First of all, you need PCB, you can order online or DIY.
When you have the PCB ready for all the holes and tin plated plates, it\'s time to start filling the board.
I made the design, and all the components were through-
So anyone can do it, but you can download it if you like a smaller version of the motherboard.
Brd file and edit all components as SMD.
Most of the resistors I use are 1% tolerances, which is because I have resistors on hand and you can use a normal 5% resistor.
Solder the resistors and jumpers, then solder the capacitors and diodes, be careful about the polarity!
If you don\'t have the same potentiometer as my package, you can weld an external potentiometer with some wires or just edit the footprint.
The inductive resistance I use is 4 w 1 ohm and you can use a different resistance but not less than 3 w.
The transistor is two TIP122 Darlington pairs, there is no need to use Darlington pairs, any BJT with a gain of more than 100 and a 2A current capability should work, but check the base resistance to match the transistor!
In addition, you can use almost any other four games
Amplifier, be sure to select a pincompatible one.
I made the board with two outputs, one with screw terminals and the other with DSI battery connectors, they are connected in parallel, but you should charge only one battery at a time.
Keep in mind that this charger is designed to charge a single battery, not in parallel and not in series.
When you have finished welding, screw the radiator to your transistor and they will consume quite a bit of power!
The one I use is fairly small and maybe should use a bigger one, but I don\'t think it will be more than 70 °C, so it\'s fine now.
Now, add a small bracket to your motherboard and it will work.
As the first Test, I\'m going to charge the 600 battery and I\'m going to charge it at 0. 5C to be safe.
First, connect the multimeter to the output and set the dial to the current in the 10A range.
Plug in the charger and turn the potentiometer until the output current is half the nominal capacity of the battery, 0 in my case. 3A.
Then, connect the battery to the charger and be careful about the polarity, in my circuit design there is a positive pole on the right side of the connector. I tested the 4.
2 v reference below VCC, as you can see in the picture, this is a perfect 4. 2v reference.
When I started charging the battery, it had an open voltage of 3.
1 v, so it\'s empty.
After about an hour and a half, the voltage of the battery is 4.
09 v, is about to enter the stage of constant voltage.
After an hour and a half, I saw the LED darkened, so I checked the current by the voltage drop on the induction resistor, the current is about 24 mA, which is less than 9% of the original 300 mA.
The battery was fully charged at that time.
This charger works very well and I tested it with 600 mAh battery, 840 mAh DSI battery, 200 mAh watch battery and 4000 mAh tablet battery.
It took them all about 3 hours to fully charge, 4Ah for a bit longer, but only because the charger was limited to 1 hour.
6A, that\'s a 0. 4C charge rate.
I hope this instructable is useful for all manufacturers that start using li-
Ion battery, all your items are good!
If there is anything you don\'t understand, or you need more detailed information, feel free to ask me and I will answer as much as I can.
If you find this instructions useful, please vote for the Epilog challenge, green design and battery --
Power competition.
Custom message
Chat Online 编辑模式下无法使用
Chat Online inputting...