PCM is suitable for Li-Ion/Li-Pol. PCM is designed to protect against overcharge and deep discharge of 1...4 batteries.
In most modern portable devices, such as tablet computers, GPS navigators, e-readers, portable game consoles, solar energy storage devices, manufacturers use unpackaged lithium-polymer batteries. The main advantages of Li-Pol batteries are their small size with an acceptable battery capacity, the ability to be manufactured for a specific device, without resorting to established standards.
It is safe to say that lithium-polymer batteries are the most “delicate” batteries in existence, that is, they require mandatory compliance with several simple but mandatory rules, due to non-compliance with which either a fire occurs or the battery “dies”.
We list them in descending order of danger:
Charge to a voltage exceeding 4.2 V per cell;
Battery short circuit;
Discharge with currents exceeding the load capacity or heating the battery above 60 °C;
Discharge below voltage 3 V per cell;
Battery heating above 60˚C;
Battery depressurization;
Storage in a discharged state.
Failure to comply with the first three points leads to a fire, all others - to complete or partial loss of capacity.
Therefore, before installation in any gadget, each open-frame battery is equipped with a controller that protects the battery from overcharging and overdischarging, controls charging and discharging currents and voltages, which significantly extends the battery life and helps ensure safety.
The controller collects and processes information related to the batteries and, using transistor switches, disconnects the batteries from power. Resistors and capacitors provide external synchronization.
Provided that the charge and discharge voltages of the batteries correspond to the norm, there is no short circuit on the battery and its capacity has not reached its maximum, the transistor switches are open and the batteries can be freely charged and discharged.
If one of the specified parameters deviates from the norm, the controller supplies a closing voltage to the transistor switches. The voltage through the high resistance of the closed transistors is not supplied to the terminals of the batteries, which is why charging or discharging the batteries stops until all the necessary conditions meet the norm.
To avoid imbalance of batteries in a Li-Pol battery, the batteries are charged separately. For this purpose, the 4SBLi-7A5021 controller is used, which has 4 separate circuits, therefore it can charge a battery of four lithium batteries.
Connection diagram:
Voltage control on each cell:
When the voltage on any of the cells exceeds the threshold values, the entire battery is automatically turned off.
Current control:
When the load current exceeds threshold values, the entire battery is automatically turned off.
Description of pins:
"B-"- general battery minus
"B1"- +3.7V
"B2"- +7.4V
"B3"- +11.1V
"B+"- general battery plus
"P-"- minus load (charger)
"P+"- plus load (charger)
"T"- NTC 10K thermistor output
Controller: S-8254A
Datasheet for S-8254A.
Specifications
Model: 4S-EBD01-4.
Number of series-connected Li-Ion batteries: 4 pcs.
Operating voltages: 11.2V... 16.8V.
Cell overcharge voltage (VCU): 4.275±0.025V.
Overdischarge voltage (VDD): 2.3±0.1V.
Rated operating current: 3A - 4A.
Threshold current (IEC): 4A - 6A.
Overcharge protection.
Overdischarge protection.
Short circuit protection.
Dimensions, mm: 15 x 46.1 x 2.62.
Weight: 2 gr.
Guarantee
Every product we sell comes with a warranty. We always meet the client halfway and try to resolve all controversial situations. For more details, you can read the terms of exchange and return in our store by following the link.Protection of lithium-ion batteries (Li-ion). I think that many of you know that, for example, inside a mobile phone battery there is also a protection circuit (protection controller), which ensures that the battery (cell, bank, etc....) is not overcharged above a voltage of 4.2 V , or discharged less than 2...3 V. Also, the protection circuit saves from short circuits by disconnecting the can itself from the consumer at the moment of a short circuit. When the battery reaches the end of its service life, you can remove the protection controller board from it and throw away the battery itself. The protection board can be useful for repairing another battery, for protecting a can (which does not have protection circuits), or you can simply connect the board to the power supply and experiment with it.
I had many protection boards for batteries that had become unusable. But a search on the Internet for the markings of the microcircuits yielded nothing, as if the microcircuits were classified. On the Internet there was documentation only for assemblies of field-effect transistors, which are included in the protection boards. Let's look at the design of a typical lithium-ion battery protection circuit. Below is a protection controller board assembled on a controller chip designated VC87 and a transistor assembly 8814 ():
In the photo we see: 1 - protection controller (the heart of the entire circuit), 2 - assembly of two field-effect transistors (I will write about them below), 3 - resistor setting the protection operation current (for example during a short circuit), 4 - power supply capacitor, 5 - resistor (for powering the controller chip), 6 - thermistor (found on some boards to control the battery temperature).
Here is another version of the controller (there is no thermistor on this board), it is assembled on a chip with the designation G2JH, and on a transistor assembly 8205A ():
Two field-effect transistors are needed so that you can separately control the charging protection (Charge) and the discharge protection (Discharge) of the battery. There were almost always datasheets for transistors, but none for controller chips!! And the other day I suddenly came across an interesting datasheet for some kind of lithium-ion battery protection controller ().
And then, out of nowhere, a miracle appeared - after comparing the circuit from the datasheet with my protection boards, I realized: The circuits match, they are one and the same thing, clone chips! After reading the datasheet, you can use similar controllers in your homemade products, and by changing the resistor value, you can increase the permissible current that the controller can deliver before the protection is triggered.
Controllers themselves are useful devices. And in order to better understand this topic, it is necessary to work with a specific example. That's why we'll look at the battery charge controller. What is he? How is it arranged? What are the specific features of the job?
What does a battery charge controller do?
It serves to monitor the recovery of energy losses and waste. First, he monitors the conversion of electrical energy into chemical energy, so that later, if necessary, the required circuits or devices can be supplied. Making a battery charge controller with your own hands is not difficult. But it can also be recovered from power supplies that have failed.
How the controller works
Of course, there is no universal scheme. But many people in their work use two triple resistors that regulate the upper and lower voltage limits. When it goes beyond the specified limits, it begins to interact with the relay windings, and it turns on. While it is working, the voltage will not drop below a certain, technically predetermined level. Here we should talk about the fact that there is a different range of boundaries. So, the battery can be set to three, five, twelve, or fifteen volts. Theoretically, everything depends on the hardware implementation. Let's look at how the battery charge controller works in different cases.
What are the types?
It should be noted that there is a significant variety that battery charge controllers can boast of. If we talk about their types, let's make a classification depending on the scope of application:
- For renewable energy sources.
- For household appliances.
- For mobile devices.
Of course, there are much more species themselves. But since we are looking at the battery charge controller from a general point of view, they will suffice for us. If we talk about those that are used for wind turbines, then their upper voltage limit is usually 15 volts, while the lower one is 12 V. In this case, the battery can generate 12 V in standard mode. The energy source is connected to it using normally closed contacts relay. What happens when the battery voltage exceeds the set 15 V? In such cases, the controller closes the relay contacts. As a result, the source of electricity from the battery is switched to the load ballast. It should be noted that they are not particularly popular with solar panels due to certain side effects. But for them they are mandatory. Household appliances and mobile devices have their own characteristics. Moreover, the battery charge controller for tablets, touchscreen and push-button cell phones are almost identical.
Let's look inside a lithium-ion cell phone battery
If you pick apart any battery, you will notice that a small one is soldered to the terminals of the cell. It is called a protection circuit. The fact is that they require constant monitoring. A typical controller circuit is a miniature board on which a circuit made of SMD components is based. It, in turn, is divided into two microcircuits - one of them is the control one, and the other is the executive one. Let's talk in more detail about the second one.
Executive scheme
It is based on There are usually two. The microcircuit itself can have 6 or 8 pins. To separately control the charge and discharge of a battery cell, two field-effect transistors are used, which are located in the same housing. So, one of them can connect or disconnect the load. The second transistor does the same actions, but with a power source (which is the charger). Thanks to this implementation scheme, you can easily influence the operation of the battery. If desired, you can use it in another place. But it should be borne in mind that the battery charge controller circuit and it itself can only be applied to devices and elements that have a limited operating range. We will now talk about such features in more detail.
Overcharge protection
The fact is that if the voltage exceeds 4.2, overheating and even an explosion may occur. For this purpose, microcircuit elements are selected that will stop charging when this indicator is reached. And usually, until the voltage reaches 4-4.1 V due to use or self-discharge, further charging will be impossible. This is an important function that is assigned to the lithium battery charge controller.
Overdischarge protection
When the voltage reaches critically low values that make the operation of the device itself problematic (usually in the range of 2.3-2.5V), the corresponding MOSFET transistor, which is responsible for supplying current to the mobile phone, is turned off. Next, there is a transition to sleep mode with minimal consumption. And there is a rather interesting aspect of the work. So, until the battery cell voltage exceeds 2.9-3.1 V, the mobile device cannot be turned on to operate in normal mode. You may have probably noticed that when you connect your phone, it shows that it is charging, but it doesn’t want to turn on and function normally.
Conclusion
As you can see, the Li-Ion battery charge controller plays an important role in ensuring the longevity of mobile devices and has a positive effect on their service life. Due to their ease of production, they can be found in almost any phone or tablet. If you want to see with your own eyes and touch with your hands the Li-Ion battery charge controller and its contents, then during disassembly you should remember that you are working with a chemical element, so you should be careful.
