Comparison of the two technologies*
Lead-acid batteries: historical advantages and limitations
The lead-acid batteries have historically been the most used for starting internal combustion engines (cars, trucks). They offer certain advantages but also significant constraints.
Pb 
Main characteristics
Low cost: these batteries are inexpensive to manufacture and recycle.
High weight: their composition makes them heavy, which limits their use in weight-sensitive mobile applications.
Limited lifespan: they support about 500 cycles at 50% discharge and only 300 cycles at 70% discharge.
Usage limitations
The power of a lead-acid battery decreases significantly during discharge, making it unsuitable for frequent deep discharges. In practice, only a portion of the nominal capacity is considered truly usable, typically between 30% and 50% of the actual capacity.
For example, a lead-acid battery with an actual capacity of 600 Ah will have a usable capacity of about 300 Ah.
Energy efficiency and recharging
During recharging, some energy is lost as heat, with a thermal loss of 15 to 20%.
Thus, if the charger provides 100 A for an hour, the battery will effectively absorb only 80 A.
Recommended usage
Lead-acid batteries are not ideal for prolonged use requiring frequent deep discharges, such as:
electric traction (electric vehicles, forklifts);
powering energy-intensive tools or equipment.
For these uses, other more efficient battery technologies (Li-ion, NiMH) are generally preferred.
Lithium technology: a leap forward compared to lead
Lithium batteries are a more recent technology than lead-acid batteries, offering many advantages, including a higher energy density. This means they store more energy for a reduced weight and volume.
Li 
Advantages of lithium batteries
High energy density: a lithium iron phosphate (LFP) battery weighs about 10 to 15 kg per kWh stored, compared to 25 to 35 kg/kWh for lead.
Increased longevity: depending on the discharge rate, an LFP battery can maintain its performance beyond 4000 charge/discharge cycles, compared to 300 to 600 cycles for a lead-acid battery at 50% depth of discharge (DoD).
Stable voltage curve: the voltage of an LFP battery remains almost constant throughout the discharge, ensuring stable energy delivery even under high currents.
Better cold performance: at -20 °C, a lithium battery can still provide 80% of its capacity, while a lead-acid battery provides only 30%.
Constraints and precautions
Mandatory electronic management: lithium batteries require a specific management system, called BMS (Battery Management System), which controls the charge, temperature, and voltage of each cell and protects the battery against overcharging and deep discharges.
Limited recharging below 0°C: due to their chemistry, lithium batteries cannot be recharged below 0 °C without risking irreversible damage.
Summary of characteristics
| Characteristic | Lead Battery (Pb) | Lithium LFP Battery |
| Mass per kWh | 25 – 35 kg/kWh | 10 – 15 kg/kWh |
| Number of useful cycles | 300 – 600 (at 50% DoD) | 2000 – 4000 (at 80% DoD) |
| Recommended depth of discharge (DoD) | ~50% | 70 – 90% |
| Voltage during discharge | Decreases significantly | Remains stable |
| Performance at low temperature (-20°C) | 30% capacity | 80% capacity |
In summary, lithium technology, particularly with LFP batteries, offers better energy density, longer lifespan, and more stable performance than lead-acid batteries. However, it requires more sophisticated electronic management and special attention to temperature conditions, especially for recharging.
*: The technical information presented in this article is provided for guidance only. It does not replace the official manufacturer's instructions. Before any installation, handling, or use, please consult the product documentation and follow the safety instructions. Torque.works cannot be held responsible for inappropriate use or incorrect interpretation of the information provided.