Lithium and lead-acid batteries are the two most commonly used battery types in electric vehicles. Lithium batteries include lithium iron phosphate (LiFePO₄) and ternary lithium batteries (NMC). If you’ve paid attention, you’ll notice that all lithium batteries come with a protection board, while lead-acid batteries usually don’t—they’re just a few cells wired together. So why the difference?
This article will break things down clearly:
- What is a battery protection board?
- How does it work?
- Why do lithium batteries need one?
- Why don’t lead-acid batteries use them?
- And can they?
What Is a Battery Protection Board?
A battery protection board is an electronic circuit designed to protect lithium batteries. It’s made up of a control chip, MOSFETs, resistors, capacitors, thermistors, and a printed circuit board (PCB).
The board works by monitoring key parameters like voltage, current, and temperature, and protecting the battery from potential dangers. Here’s how it works:
How Does the Protection Board Work?
1. Overcharge Protection
When a lithium battery charges, the control chip keeps a close eye on the voltage and temperature. If any cell hits the preset overcharge limit, the chip tells the MOSFETs to shut off charging.
This prevents overheating and thermal runaway, which could lead to swelling or even fire.
2. Over-discharge Protection
Discharging the battery too much can damage the cells and shorten its lifespan.
So, if the voltage drops below a set threshold, the board will cut off power to stop the battery from discharging too far.
This is why your electric scooter might suddenly shut off when the battery is still at 20–30%—the board is protecting the battery from deep discharge.
3. Overcurrent Protection
While lithium batteries can handle high current, too much current can lead to overheating, especially with NMC batteries, which are more heat-sensitive.
If the board detects current beyond the safe limit, it cuts the circuit to avoid fires or damage.
4. Short-Circuit Protection
Lithium batteries are made of dozens or even hundreds of cells, often packed tightly. Over time, if mishandled or overcharged, dendrites can form inside the cells and pierce through the separator, causing a short.
If a short-circuit happens, the protection board detects the spike in current and immediately cuts the circuit to prevent the battery from catching fire.
5. Temperature Protection
Both the battery and the board generate heat during use. A temperature sensor (thermistor) constantly monitors this. If the temperature rises too high, the control chip shuts off charging or discharging to prevent overheating and potential hazards.
6. Cell Balancing
A lithium battery pack is made up of many cells. Over time, voltage and capacity differences develop between cells.
The protection board balances the voltage across all cells, improving battery performance, reducing aging, and extending its life.
Why Do Lithium Batteries Need a Protection Board?
Without a protection board, lithium batteries are at risk of:
- Overcharging
- Over-discharging
- Overcurrent
- Short circuits
- Overheating
These risks can lead to thermal runaway, swelling, fires, or even explosions. The protection board ensures safe operation and helps extend the battery’s service life by maintaining balance between all cells.
Why Don’t Lead-Acid Batteries Need a Protection Board?
There are a few key reasons:
- Chemical stability: Lead-acid batteries are chemically more stable. Even if they are overcharged, over-discharged, or short-circuited, they don’t easily catch fire or explode.
- Tolerance: They can handle a wider range of charge/discharge without major damage.
- Cell consistency: A typical lead-acid battery is made up of only 4–6 cells, and their voltage is usually well balanced.
Because of these factors, lead-acid batteries don’t need a complex protection system like lithium batteries do.
Can Lead-Acid Batteries Use a Protection Board?
Yes, they absolutely can.
While not necessary for safety reasons, a protection board can help prevent overcharging, deep discharging, and overheating, especially when fast charging or when the battery is used for long periods.
This can reduce aging, protect battery health, and help extend the lifespan of a lead-acid battery.
Final Thoughts
Lithium batteries are more sensitive and active in terms of chemistry. Without a protection board, they’re more likely to overheat, catch fire, or degrade quickly. That’s why a protection board is essential—it keeps the cells balanced and protects against serious failure.
Lead-acid batteries are safer and more tolerant. They don’t require a protection board, but using one can still be beneficial—it can help avoid performance drops caused by poor charging habits or overuse.
Want your battery to last longer and work safer? Then whether it’s lithium or lead-acid, giving it the right protection always pays off.