18650 Battery Protection Circuit: Introduction and Discharging

Believe it or not, but the protection circuit is one of the pivotal aspects of 18650 batteries. Not having protection circuits would give us several disadvantages that can render the battery useless. Hence, this article will introduce everything about battery protection circuit, from its introduction, discharging, creation, and everything that is related to it.

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18650 Battery Holder With Protection Circuit

Protected Lithium-Ion (Li-ion) batteries include a small electronic circuit incorporated into the cell packing. This circuit safeguards the battery from overcharge, over discharge, short circuit/over current, and overheating. Protected 18650 batteries are safer to use in your electronics. Protected batteries are less likely to catch fire and cause injury to people or property.

Most shielded batteries have the following components:

●PTC: Protects against overheating and, as a result, overcurrent. It will be automatically reset.

●The CID or Pressure Valve: will permanently close the cell if the pressure in the cell is too high (Can be due to over charge).

●The PCB: protect against over discharge, over charge, and over current, depending on the design. The PCB will automatically reset when it is plugged into a charger.

●This electrical circuit is not present in unprotected batteries' cell packing. They can have higher capacity and current capability than a shielded cell as a result of this. There is, however, always the risk of overheating, short circuiting, or over discharging. Unprotected batteries are also significantly less expensive.

18650 Battery Discharge Protection Circuit

Protected cell 18650 batteries are highly recommended. A protection circuit in protected cells prevents the cell from being overcharged. Unless the battery is safeguarded by appropriate circuitry, unprotected cells can overcharge and explode, causing a fire. Only use the popular LG HG2 and Samsung 25r batteries in devices that are meant to handle unprotected 18650s.

Seeing the importance of protection circuits, we should know how to make it. In this article, we will show you how to use a simple life hack to protect any 18650 cell. 

To make it, all you need is an old phone battery and some cords. The built-in safety circuit in Lithium ion batteries used in phones turns off the gadget if the cell voltage goes below 3 volts. The battery will not be overcharged as a result of this. Any Lithium ion cell, such as an 18650, may be utilized with this protection circuit. A protection circuit is not included in the 18650s that have been salvaged (from a laptop) or the cheap 18650s.

Step 1. Get the materials you need.

You'll need:

●a multimeter

●a soldering iron

●a wire cutter

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●some cords

●an old phone battery

●an 18650 or whichever Lithium ion cell you want to save

Step 2. Using your cutting instrument, try to gain access to the battery. Be careful not to short the circuit, since this might cause a fire! Examine the circuit's input wires to see which one is positive and which is negative. On the PCB, there are three output pins. One is the signal pin, while the others are the negative and positive outputs. You can see the + and - signs on the battery, which indicate which output pins are active. Solder the 18650 to the circuit if it was recovered.

Step 3. Prepare four copper wire pieces.

Step 4. Using some wires, easily solder the circuit and the battery together. Make that the polarity is correct and that the battery is not shorted. Keep your soldering iron away from the battery for as long as possible.

Step 5. Test the output voltage using your multimeter. If everything seems good, you're done. Because the cell is secured, you may utilize it for any project right now. That is all there is to it.

How can you tell if a 18650 battery is protected?

Here are some techniques for determining whether or not an 18650 battery is protected.

●An 18650 battery has a diameter of 18 millimeters and a length of 65 millimeters. Protected 18650 batteries, on the other hand, measure 18.2 millimeters in diameter and 69 millimeters in length.

●There is only one layer of packaging on a common 18650 battery. On the other hand, a protected 18650 battery will be packed in two layers. The original packaging of the battery is the first, while the supplementary packaging that conceals the protective circuit and its metallic connecting tabs is the second.

●Tabs currently open: - A standard 18650 battery has no metallic tabs, or if it does, they are little tabs measuring 20 millimeters in length that extend from each of the cell's terminals and are designed to be used as connecting terminals. A protected battery, on the other hand, has a tab connecting the battery's positive and negative terminals to the protective circuit.

To establish if a battery is protected or not, utilize one of the three techniques given above.

Will the cell just explode if the protective circuit is removed and it is mistreated?

Of course, the answer is no, but it may be easily destroyed beyond repair. The built-in safety is designed to keep the cell safe from fire and explosions, not to keep it safe from harm.

Inside the container, a cell can have two types of protection:

●One is a pressure valve, which will usually permanently disconnect the battery when it vents. This is referred to as a CID (Current Interrupt Device). When a cell vents, it does so with a lot of force, which may blow the front and rear of a flashlight out. This isn't a flaw; it's the last line of defense against the cell exploding.

●The second type of protection is a PTC, or temperature sensitive resistor. It will have a very low resistance at room temperature, but at a certain temperature, the resistance will grow dramatically, decreasing the current flow. When a PTC cools down, it resets, potentially compromising the cell's performance. HRL (Heat Resistive Layer), which disables the battery if it becomes too hot, augments or replaces this function in certain modern cells.