Battery Protection Circuits – Introduction and Comparison

Did you know that batteries cause a lot of hazardous damage? Many battery users don’t know this, and it becomes very dangerous for the environment and for their devices.

Luckily, modern batteries, especially lithium batteries, are designed with a protection circuit. This is the part that protects the battery from overcharging or draining too low.

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In this guide, we will be discussing protection circuits for lithium batteries.

lithium battery Protection Circuits

Lithium batteries are the most preferred battery technology because of their high energy density. However, that much power does not come easily, and they require cautious handling, more than any other battery type.

Besides, the batteries are relatively more expensive. And hence, one must try to get as much use from them as possible.

Battery protection circuits can increase the lifespan of your battery. It helps protect them from overheating, overcharging, and draining.

Overcharge: Lithium batteries take charge of up to 4.2 volts. Anything beyond this can cause damage to the battery and becomes hazardous. Most fires started by batteries have been due to overcharging and negligence. A battery protection circuit is necessary for preventing this.

Over-draining: On the lower side, lithium batteries can discharge safely to about 2.5V. Discharging them lower than this can be stressful to the cell and reduce its lifespan. A protection circuit cuts off the circuit connect when the battery nears this level, keeping it safe.

Quick discharge: Another factor that reduces battery life is discharging too fast. Lithium batteries cannot withstand this. They come with a maximum discharge current rating that should be observed. A battery protection circuit removes the battery from the circuit in case of too much load current.

Lithium batteries need protection circuits. Generally, protection comes in a circuit board joined to the batteries before being wrapped and distributed.

The primary function of these circuits is to ensure the rechargeable battery never overcharges or drains too low.

Lithium batteries promise about 3.7volts of power. The entire current should not go beyond the maximum of 4.2V.

And when discharging, it is crucial to keep the voltage to or above the minimum level. In this case, it should never drain too low below 2.8V.

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These are factors that affect lithium-ion battery lifespan. Hence, the batteries need protection to stay out of danger at all times. The circuit will shut the battery down whenever abnormal voltages are detected.

Every user must check their lithium batteries periodically using a voltage meter. This allows you to understand how well your batteries are charging or discharging.

Aside from these, some chargers will stop charging when the lithium battery is close enough to 4.2V, keeping the charging range in the safe zone.

Even if your device does not have a way of shutting down when the battery is too low, battery protection circuits will force a shutdown. That is how important they are.

How Lithium Protection Circuits Work

Protections circuits can seem a bit complicated if you observe all the hard terms. But it’s not.

Here is a breakdown of how it all works:

The protection circuit is a device built in the cell. It acts as the protector to help block an increase in a current surge.

In a circuit interrupt device, it opens the electrical path in case of extremely high voltage. This action raises the inner cell pressure to about 150 psi.

Safety vents inside the batteries enable a controlled distribution of gas when the pressure increase.

Protections circuits can also be placed outside the cells. They open up a strong state switch when the voltage goes to about 4.3V. This is the maximum charge, and it becomes a danger if it goes beyond.

A protection circuit features a fuse, which cuts through the current flow if the battery temperature reaches about 90 degrees Celsius. A quality control circuit cuts off about 2.5v of the current path in case of overcharging.

Well, a protection circuit is a crucial feature in any battery pack. It assures safety for the users. However, you must know every safety precaution is only effective if the operational mode comes from outside. For instance, modes from electrical shorts or faulty chargers can present the best function in these safety modules.

Reverse Battery Protection Circuits

Battery protection is, without a doubt, a sensitive matter. We all want to be safe when using batteries, and protection circuits are the most basic way to achieve this.

Reverse battery protection circuits are also a good way to keep your electronics safe. These include:

Reverse Battery Protection Using Diode

This is the easiest way to achieve reverse battery protection. It is a series diode in the positive supply line to the ECU. This should be chosen according to the load. When you put the battery in the wrong polarity, the PN junction blocks its voltage. As a result, the electronics are kept way out of harm’s way.

Reverse Battery Protection Using n-charging MOSFET

A MOSFET is the best choice when you want to lower the power lost from reverse protection. This includes inserting the device in the right direction in the positive supply line. Such an action protects the load against reversal battery. MOSFET features an anti-parallel body diode, making them ideal for this work.

When using this method, the MOSFET is fully turned on towards the correct direction. Now, since the Source is at a higher potential, the MOSFET is on the high side. That means it does not reference the ground. Boosting the gate voltage is necessary, in which case you need a pump circuit or something like that.

Using a p-channel MOSFET

A third solution would be to use a p-channel MOSFET for reverse battery protection. Simply connect p-channel MOSFET in the positive supply route of the load.

Do batteries have short circuit protection?

Most batteries today are built with three crucial components:

PTC: This part protects batteries from over-heating and direct over current.

CID or Pressure Wave. This part will disable the battery permanently in case of too high pressure

PCB: This is a component that protects the batteries against over-discharging, overcharging, and over current.

You can find some unprotected cells that do not come with an electronic circuit in the cell packaging. Therefore, they offer more capacity and current. But they can always overheat, short-circuit, or over-drain. It would be best to buy protected batteries.