1. Charging and Discharging Efficiency: Lithium-ion Batteries Win Outright, Faster Start-Stop Response
At the moment of starting and stopping a car, the battery needs to quickly release a large current to drive the starter motor. Simultaneously, after the engine starts, it needs to quickly receive charging from the alternator. Lithium-ion batteries have significantly higher charge and discharge efficiency than lead-acid batteries. Their discharge rate typically reaches 2C-5C (meaning they can release 2-5 times their own capacity in one hour), while lead-acid batteries generally only reach 1C-2C.
In actual use, vehicles equipped with lithium-ion batteries respond much faster to start-stop, with almost no noticeable delay. Lead-acid batteries, after frequent start-stop cycles, are prone to delayed charging and discharging, potentially leading to weak starting and start-stop function failure. The advantages of lithium-ion batteries are even more pronounced in low-temperature environments—the capacity and discharge performance of lead-acid batteries decrease significantly with sudden temperature drops, while lithium-ion batteries exhibit more stable low-temperature characteristics, maintaining good charge and discharge capabilities even at -20°C.
2. Cycle Life: Lithium-ion batteries have a lifespan 2-3 times that of lead-acid batteries.
Cycle life refers to the number of times a battery completes one charge-discharge cycle (from full charge to discharge to a specified voltage and then fully charge), directly determining the battery's lifespan. Lead-acid start-stop batteries typically have a cycle life of around 1000-1500 cycles, with a normal service life of about 2-3 years; while lithium iron phosphate start-stop batteries can have a cycle life of 3000-5000 cycles, with a service life of 5-8 years, and some high-quality products can even exceed 10 years.
The core reason for this difference lies in the stability of the battery materials. During the charge-discharge cycle, lead-acid batteries experience sulfation of the electrodes, which leads to capacity decay over time; lithium batteries, on the other hand, have a more stable electrode material structure, are less prone to such losses, and have stronger cycle durability. For car owners who frequently drive in congested urban areas and have high start-stop frequency, the long lifespan advantage of lithium batteries is even more pronounced.
3. Energy Density: Lithium Batteries are Lighter, Contributing to Overall Vehicle Energy Efficiency
Energy density refers to the amount of electricity stored per unit weight or volume of battery, directly affecting the battery's weight and volume. The energy density of lithium batteries is approximately 100-150 Wh/kg, while that of lead-acid batteries is only 30-50 Wh/kg. In other words, for the same capacity, lithium batteries weigh only 1/3 to 1/2 the weight of lead-acid batteries.
For example, a common 12V 60Ah start-stop battery weighs approximately 15-18kg for lead-acid batteries, while a lithium battery weighs only 5-8kg. This lighter battery reduces the overall vehicle load, thus reducing fuel consumption and aligning with the energy-saving goals of start-stop systems. Furthermore, lithium batteries are smaller and more adaptable during installation, making them a more flexible choice for vehicles with limited engine compartment space.
II. Cost and Maintenance: Lead-acid batteries offer high cost-effectiveness, while lithium batteries are worry-free and convenient.
Besides performance, cost and maintenance costs are also key concerns for car owners. In this aspect, both have their advantages and disadvantages.
1. Initial Purchase Cost: Lead-acid Batteries Offer a Greater Advantage
Currently, the price of a 12V start-stop lead-acid battery on the market typically ranges from 500 to 1500 yuan. Ordinary EFB lead-acid batteries are cheaper, around 500-800 yuan, while high-end AGM lead-acid batteries are slightly more expensive, around 800-1500 yuan. Start-stop lithium batteries, on the other hand, range from 1500 to 3000 yuan, with some imported brands even more expensive. The initial purchase cost is 2-3 times that of lead-acid batteries.
For car owners with limited budgets and a short vehicle lifespan (planning to replace the car within 3 years), the high cost-effectiveness of lead-acid batteries is more attractive. However, for car owners who plan to use their vehicles for a long time and prioritize durability and peace of mind, although lithium batteries have a higher initial cost, the annual cost is actually lower over the long term.
2. Maintenance Costs: Lithium-ion batteries are virtually maintenance-free, while lead-acid batteries require regular checks.
Lead-acid batteries require regular checks of the electrolyte level (for flooded lead-acid batteries). If the level is too low, distilled water needs to be added; otherwise, battery performance and lifespan will be affected. Additionally, the battery terminals must be checked for oxidation, leakage, and other issues, resulting in a relatively high maintenance frequency.
Lithium-ion batteries, on the other hand, use a sealed structure and do not require electrolyte replenishment. They also do not experience leakage or gas evolution issues. Daily use requires almost no additional maintenance; only regular checks of the connections for tightness are necessary. For car owners unfamiliar with vehicle maintenance or with busy driving habits, the maintenance-free nature of lithium-ion batteries saves considerable time and effort.
III. Safety: Both offer guarantees; product quality is key.
When discussing batteries, safety is an unavoidable topic. Many people worry that lithium-ion batteries are prone to "catching fire and exploding." However, with the maturity of technology, high-quality start-stop lithium-ion batteries (especially lithium iron phosphate batteries) have very high safety levels.
Lithium iron phosphate batteries boast excellent thermal stability, with a decomposition temperature exceeding 600℃, while lead-acid batteries decompose at approximately 200℃. Furthermore, lithium batteries are equipped with a comprehensive Battery Management System (BMS) that monitors battery voltage, current, and temperature in real time. In case of overcharging, over-discharging, or short circuits, the system immediately activates its protection mechanism, cutting off the circuit to prevent safety hazards.
Lead-acid batteries have also undergone long-term market validation, demonstrating mature and stable technology. With normal use and avoidance of over-discharge and short circuits, safety issues are generally not a concern. It is important to note that whether using lithium or lead-acid batteries, it is crucial to choose reputable brands and products that meet the original vehicle specifications. The safety of inferior batteries cannot be guaranteed.
