Custom Charging

Lithium ion batteries have charging voltage and current limits. They must use the "constant current/constant voltage (CC/CV)" charging method. The battery is first charged by a set constant current until it reaches a set voltage, then charged with this constant voltage until the current falls below a set value. If charging exceeds this limit, the battery will be permanently damaged and there is a risk of fire or explosion. The charging system also affects battery performance such as runtime and cycle life. Therefore, charging must be strictly controlled. Special consideration is required when designing a charging system to ensure the battery is both fully charged and not over charged. Modern charge ICs apply a few more steps to the process to increase safety. These ICs monitor the cell temperature and have a programmable cut-out function that stops charging the cell after a pre-set period.

When designing a charger, pay attention to the battery voltage, capacity, maximum charging current, and charging temperature conditions. Then consider the power constraints and whether you want to use a linear or switch-mode charger. Linear chargers are generally more cost-effective and smaller, which makes them ideal for simple circuits and charging currents of less than one amperere. Switch-mode chargers are more efficient and ideal for fast charging.

At low charging current C rates (0.5C or less), lithium ions are smoothly embedded in the graphite sheet without damaging the electrodes. As the charging rate increases, this embedding becomes stiffer and stiffer. If the charging rate is too high, the lithium ions will not have time to penetrate the electrodes properly and will only be deposited on the surface of the electrodes, which will cause the battery to age prematurely. Depending on how long your application needs to be charged, you will need to find the right compromise between the necessary charging time, speed, and battery aging. It is recommended to lower the maximum charging current C rate and limit the charging rate to 0.5C or less.

Most lithium ion batteries use a graphite type material in one electrode. The increase in charging temperature can cause the graphite flakes to peel off, accelerating the permanent capacity loss of the battery. A high charging current rate increases temperatures and accelerate battery capacity loss. High temperatures cause electrochemistry to produce gases within the battery, which accelerates chemical aging. Depending on the cell structure, high temperatures can also cause cells to swell. When the battery housing or device position can not support it, this deformation can pose a safety hazard risk. Lithium ion batteries do not like extreme temperatures. Most lithium ion batteries can only withstand a maximum temperature of 60°C, and it is recommended to charge at a maximum temperature of 45°C under a charge rate of 0.5C or less. Very few batteries can be charged below 0°C. Lithium deposits may be generated, resulting in permanent capacity loss. It is recommended to charge the battery at a very slow rate of 0.05C at temperatures below 0°C.

A proper charging system is critical to battery performance. We use the world high precise circuit components to monitor and control the current and voltage statues. The chargers are compact, portable, universal and safe. It can be customized with various outputs, to meet different demands. With CPU control and PWM technology they have the advantages as high efficiency, good stability, low-carbon and energy saving. Three section charging modes can control the charging current and voltage automatically and precisely and both ensure that battery is charged fully and not over charged.