A good charger provides the base for batteries that perform well and are durable. Charging correctly is very important for lithium batteries to get them to perform well. If the lithium battery is not charged in the proper manner, the working of the battery can be impacted or the battery can get damaged. The correct and proper charging of the battery results in a long operation life. In today’s market, chargers are not given the priority that they deserve.
Lithium-based chargers operate on constant current constant voltage (CCCV). This means that the charge current is constant and the voltage is capped when it reaches a set limit. As the voltage limit is reached, the battery saturates and the current drops until the battery can no longer charge. It is important to keep in mind that each battery has its own low-current threshold.
Types of chargers
Commonly, chargers are identified by their charging speed. The most basic charger is the overnight charger, which is also known as the slow charger. Slow chargers do not have a full-charge detection. To fully charge an empty battery using a slow charger takes anywhere between 14 to 16 hours.
Then there is the rapid charger. It falls in between the slow and fast charger and is most commonly used in consumer products. A rapid charger takes around 3 to 6 hours to fully charge an empty battery. Temperature sensing is included in most rapid chargers to safely charge a faulty battery.
Then comes the fast charger. As the name suggests it takes the shortest time to charge a battery. A fast charger can charge a battery in a little over an hour. However, though these fast chargers seem appealing, it is not recommended to use them frequently on lithium batteries as they might damage the battery.
It is also important to remember that lithium batteries have minimal losses during charge. At 1C, the battery charges to 70 percent state-of-charge (SoC) in less than an hour; the extra time is devoted to the saturation charge. It is better not to fully charge lithium batteries. It will make the batteries last longer, but the run time will be a little less. Of all the chargers available in the market, Li-On is the simplest.
Things to keep in mind while buying a charger
- It is important to use the correct charger for the intended battery chemistry. Most chargers available in the market serve one chemistry only. It is necessary to mek sure that the battery voltage agrees with the charger.
- Charging a battery is effective when the State of Charge (SoC) is low. The charge acceptance of a battery decreases when the SoC of the battery reaches 70% or higher.
- Filling a battery beyond its full SoC turns the excess energy into heat and gas. In lithium batteries this can result in a deposit of unwanted materials. Over charging the battery too much can result in permanent damage. ‘
- A fast charger or a charger with high wattage does shorten the charge time but there are limitations to how fast a particular battery can be charged. Fast charging can case stress to the batteries.
- Chargers should have a temperature override to end the charge on a faulty battery.
- One must observe the charge temperature. Lithium batteries should not rise more than 10ºC above ambient when reaching full charge.
- One should charge the batteries at room temperature. The charge acceptance of the battery drops when it is cold. Lithium batteries cannot be charged below freezing.