Frequently Asked Questions About Lithium Starting Batteries

1. Why is a lithium-ion starting battery more cost-effective than a lead-acid battery?

A lithium-ion starting battery uses lithium iron phosphate (LiFePO₄) cells as its energy storage medium. LiFePO₄ batteries can withstand 2,000 to 3,000 deep charge-discharge cycles, whereas lead-acid batteries typically last only 150 to 300 cycles. When a parking air conditioner is installed in the vehicle, the starting battery undergoes more than 200 deep cycles per year. For a LiFePO₄ battery, this translates to about 10 years of service life, while a lead-acid battery would need replacement after just one year. On average, the lifespan of a LiFePO₄ battery is 5 to 10 times that of a lead-acid battery, yet its price is less than three times that of a lead-acid unit. The cost savings are therefore obvious.

2. Are lithium-ion starting batteries safe?

The main safety concerns with lithium batteries stem from poor cell quality and improper usage. Cell quality issues arise from defective raw materials or manufacturing flaws. After over a decade of development, the quality of lithium cells has improved significantly; low-grade materials and outdated processes have been largely eliminated. Choosing cells from reputable, large-scale manufacturers ensures reliable quality. Improper usage includes overcharging, over-discharging, overheating, charging at low temperatures, excessive current, and short circuits. A starting battery equipped with a Battery Management System (BMS) can prevent all these misuse scenarios, thereby eliminating safety risks caused by improper operation.

Different types of lithium batteries have varying performance characteristics. In terms of safety, lithium iron phosphate (LiFePO₄) far outperforms other lithium chemistries. Even under extreme tests such as nail penetration or crushing, LiFePO₄ cells do not catch fire or explode.

3. Can a lithium-ion starting battery be used in parallel with a lead-acid battery?

Yes, a lithium starting battery can be connected in parallel with a lead-acid battery, but two points must be noted:

• Sparks during connection: When connecting the two batteries in parallel, there will be an instantaneous spark. Therefore, keep the connection away from flammable or explosive objects, such as gas stations or vehicles carrying hazardous materials. To reduce spark intensity, you can discharge the lithium battery until its BMS activates protection, and fully charge the lead-acid battery before connecting. If you wait until the lithium battery enters sleep mode (after being idle for about 16 hours), no spark will occur when connecting.
• Avoid pairing with a dying lead-acid battery: Do not connect a lithium battery in parallel with a lead-acid battery that is near the end of its life (e.g., one that can barely start the engine on its own). Such a lead-acid battery holds almost no usable energy and becomes a burden rather than a helper—it will not extend discharge time but instead reduce the effective capacity of the lithium battery.

The advantage of paralleling lithium and lead-acid batteries is that they complement each other, extending the overall lifespan. Notably, lead-acid batteries perform better at low temperatures. In cold weather, the lead-acid battery can handle engine starting, while the lithium battery takes over for other loads, avoiding the need to wait for heating.

4. How can I avoid running out of power for starting when using a parking air conditioner, cooking, or boiling water?

Relying solely on voltage readings to judge remaining battery capacity is unreliable. Due to the dynamic internal resistance of batteries, the voltage drop varies with different currents. Under the same state of charge (SOC), the total voltage can differ depending on the load. Additionally, temperature affects voltage readings. As a result, judging remaining power by voltage often leads to misjudgment, leaving you unable to start the vehicle.

A lithium-ion starting battery equipped with a BMS solves this problem. The BMS has a coulomb counting function that accurately tracks how much energy has been charged and discharged, providing precise SOC information. This allows the system to reserve a certain amount of energy specifically for starting, preventing accidental over-discharge. In winter, the BMS can also reserve power for battery heating, ensuring reliable starting even in cold conditions.