How long does it take to charge a 48v lithium ion battery?

Charging a New Lithium-Ion Battery: Key Considerations

When you first charge a new lithium-ion battery, it's important to follow these guidelines:

• For the first charge, simply treat it like a regular charge—there's no need for any special precautions. Once the battery is fully charged, you can unplug it and start using it immediately. It typically takes around 2-4 hours to charge fully.
• Avoid charging the battery for more than 8-12 hours, as this could potentially damage the battery and shorten its lifespan. While lithium batteries automatically stop charging once they're full, leaving them plugged in for extended periods could trigger a repeated charge-discharge cycle, which may affect the battery's protective circuitry and put it at risk.
• Shallow discharging and charging is generally better for lithium batteries. Deep discharges and full charges are only necessary when the device’s power management system is calibrating the battery. In everyday use, there's no need to wait until the battery is completely drained before charging—just charge it as needed for convenience.

Common Misconceptions About Lithium Battery Activation and Charging

Contrary to common misconceptions, lithium-ion batteries do not require activation through extended charging sessions. They are already activated before leaving the factory. The 12-hour charge recommendation is outdated and applies to nickel-cadmium and early nickel-metal hydride batteries, not lithium-ion. Lithium-ion batteries lack a memory effect, so prolonged charging can negatively impact their lifespan.

So how to properly charge a 48v lithium-ion battery? 

Charging a lithium-ion battery involves four distinct stages:

Stage 1: Trickle Charging — Trickle charging is used to pre-charge a completely discharged battery (also known as recovery charging). When the battery voltage drops below about 3V, a constant current of up to 0.1C is applied to begin charging the battery.

Stage 2: Constant Current Charging — Once the battery voltage rises above the trickle charging threshold, the charging current is increased to enter the constant current phase. The current in this phase typically ranges from 0.2C to 1.0C. The current does not need to be precisely constant; a nearly constant current is acceptable. In linear charger designs, the current often increases as the battery voltage rises to minimize heat generation in the transistors. Charging at currents greater than 1C does not shorten the total charging time, so it is not recommended. Higher charging currents cause the battery voltage to rise more quickly due to overvoltage on the electrode reactions and increased internal resistance. While the constant current phase may be shorter, the corresponding increase in time during the constant voltage stage means the total charging time does not change significantly.

Stage 3: Constant Voltage Charging — When the battery voltage reaches 4.2V, the constant current phase ends, and constant voltage charging begins. To ensure optimal performance, the voltage regulation tolerance should be no greater than +1%.

Stage 4: Charging Termination — Unlike nickel-based batteries, it is not recommended to continue trickle charging a lithium-ion battery. Continuous trickle charging can cause lithium plating on the electrodes, which makes the battery unstable and may lead to a sudden, rapid failure.

There are two typical methods for terminating the charge: monitoring the minimum charging current or using a timer (or a combination of both). The minimum current method monitors the charging current during the constant voltage phase, terminating charging when the current drops to a range between 0.02C and 0.07C. The second method involves starting a timer at the beginning of the constant voltage phase and terminating charging after two hours.

Completing the full charge cycle for a fully discharged battery typically takes around 2.5 to 3 hours. Advanced chargers include additional safety features. For example, if the battery temperature falls outside the specified range (usually 0°C to 45°C), charging will be paused.

Assessing Full Charge

To determine if a lithium-ion battery is fully charged, look for two indicators:

• The current has dropped to 0.01C.
• The total charging time does not surpass eight hours.

If the battery does not reach 0.01C within eight hours, it may be considered defective.

Conclusion

Whether you're charging an electric bike, an electric scooter, or any other device powered by a 48V battery, following these best practices will help you get the most out of your lithium battery for years to come.

Wishing you smooth charging and an enjoyable experience with the freedom and convenience that lithium batteries provide!