Differences Between Lithium-ion and Lead-Acid Batteries

Lithium-ion charging employs a Constant Current (CC) phase until the cell voltage reaches 4.2V, followed by a Constant Voltage (CV) phase where voltage is maintained and current is monitored. Charging terminates when the current drops below a specified threshold. Due to their sensitivity to overcharging, lithium-ion batteries require sophisticated protection circuits. For a single cell with a nominal 3.6V, the maximum charge voltage is 4.2V, with a typical tolerance of ≤±1%.

Constant Current (CC) Charging: A fixed current (e.g., 0.2C, where C is the battery's capacity rating) is applied, causing the voltage to rise gradually. This stage lasts until the voltage approaches the peak charge voltage (e.g., 4.2V).

Constant Voltage (CV) Charging: Voltage is held constant at the peak level, while the current steadily decreases as the battery saturates. Charging is complete when the current falls to a predefined cutoff level (e.g., 0.01C). The total CC+CV charging time should typically not exceed eight hours.

Always follow the standard charging time and procedure, including the initial cycles.

Initiate charging promptly upon receiving a low-battery warning.

No special "activation" is needed. Lithium-ion batteries are activated through normal use. The common myth of "initial 12-hour long charges" is ineffective.

The ideal charging current for lead-acid batteries is pulsed. A simple and cost-effective method involves using unfiltered pulsating DC, rectified directly from AC mains (50/60 Hz). Given their relatively high self-discharge rate, constant voltage charging is often used, especially at line frequency.

Pulse Charging: Simple and economical. Enables high currents and fast charging, but current fluctuates with line voltage variations.

Constant Current (CC) Charging: Uses a low current to prevent excessive temperature rise and electrolyte loss, resulting in long charge times. Requires overcharge protection circuits to prevent damage from prolonged charging.

Constant Voltage (CV) Charging: A safe method when the voltage is set below the upper limit (e.g., for a 12V battery). It allows for extended charging without significant risk and supports float maintenance.

Using a lithium-ion charger for NiMH/NiCd batteries will result in undercharging and reduced runtime. Using a NiMH/NiCd charger for lithium-ion batteries will cause dangerous overcharging and severely degrade lifespan. Lead-acid chargers typically have a higher output voltage than lithium-ion requirements. While lithium-ion batteries have built-in protection against overcharge, if this BMS fails, using a lead-acid charger can cause battery swelling, deformation, and serious safety hazards.