Lithium Battery Chargers Explained
Still widely used worldwide, lithium batteries were first introduced back in the late 20th century, and since then, they have played a pivotal role in modern day technology. But what sets lithium batteries apart from other types of batteries? Well, this type of battery has metallic lithium as an anode and are also known as lithium-metal batteries.
What sets them apart from other types of batteries is that they have a high charge density and high cost per unit, ultimately, offering an excellent level of performance in return. However, something that’s vital to note when using lithium batteries is that they must be charged correctly to avoid long-term damage.
Correctly Charging Lithium Batteries
If a lithium battery isn’t charged correctly, the functionality and performance of the battery’s operation can be affected, and in extreme cases, the battery can even become so damaged that it becomes unusable. With this in mind, it’s essential that lithium batteries are charged correctly to avoid them becoming destroyed.
The correct charging of lithium batteries enables the best performance and enhances the longevity of the life of the battery. Using a battery management system for charging, controls the level of charge, discharge and the rates at which charging occurs.
Charging lithium batteries is very different from charging Ni-Cads or NiMH batteries as lithium batteries are voltage sensitive rather than current based. When charging a lithium battery, you may find it’s like charging lead-acid batteries.
However, lithium batteries have a higher voltage per cell and require much tighter voltage tolerance on detecting full charge. In addition, once fully charged, they don’t allow or need to be trickle or float charged.
But what does trickle charging mean? It means charging a fully charged battery at a rate that is equal to its self-discharge rate. This enables the battery to remain at its fully charged level. Charging in this manner will not keep a battery charged if the current is being drawn by a load.
It is particularly important to be able to detect the full charge state accurately because lithium batteries do not tolerate overcharging, and again, can become easily destroyed.
Most consumer orientated lithium batteries charge to a voltage of 4.2 volts per cell, and this has a tolerance of around ± 50 mV per cell. Charging beyond this causes stress to the cell and results in oxidation that reduces service life and capacity. It can also cause safety issues too.
The charging and discharging of lithium batteries is key to their operation and long-term performance. Typically, battery management chips are incorporated into most lithium battery packs which manage the charging and discharging of the battery. In this way, the user can plug the battery into a charger and leave it to charge in the knowledge that it does not have to be unplugged after a particular time. The battery management chip will also ensure the battery is not discharged too far. The issue is to ensure that the battery management understands the exact state of the battery charge.