Lithium Ion Charging: Constant Current vs Constant Voltage

[redwan hasan]

Good afternoon.

I was going to make a 4.2v Lithium ion charger circuit, but so far what i have learned is, i will be needing constant current charger, so my question is what will happen if i charge with constant voltage? Like from a regulator maybe a linear one and i give like 4/4.1 volt constant.

Any help will be highly appreciated.

 

[milesyoung]

You can charge a lithium-ion battery using a voltage source, but you have to limit the current the battery can draw to protect the battery chemistry from deteriorating (and also for safety reasons). Usually the best way is to charge it first using a current source and then switch to a voltage source at a specified level of battery voltage. You can find many easy to use solutions that handle both stages in a single package, e.g.:
http://www.linear.com/product/LT1512

You can read more here:
http://www.digikey.com/en/articles/techzone/2012/sep/a-designers-guide-to-lithium-battery-charging

 

[meBigGuy]

You must buy a lithium-ion battery charger controller. Lithium-ion batteries require multiple phases of charging and the voltage across them must never exceed 4.2V. Basically they require A> Precharge, B> Constant Current, C> constant voltage. There are no shortcuts. milesyoung's links are good, especially the digikey link.

http://www.digikey.com/en/articles/techzone/2012/sep/a-designers-guide-to-lithium-battery-charging

 

[sophiecentaur]

A thread on this topic has just been closed on the basis of safety. Charging lithium ion batteries safely is a specialised business and should be left to the experts - or you need to become one yourself.
In any case, just how expensive are those chargers?

 

[alphy]

Good afternoon,

I can provide some insight on the difference between constant current and constant voltage charging for lithium ion batteries.

Constant current charging involves supplying a steady flow of current to the battery until it reaches a certain voltage, typically 4.2 volts for lithium ion batteries. This type of charging ensures that the battery is charged at a safe and controlled rate, preventing overheating and damage to the battery.

On the other hand, constant voltage charging involves supplying a steady voltage to the battery until it reaches a certain current level. This type of charging is commonly used in fast charging methods, as it allows for a higher initial current flow to the battery. However, it can also lead to overheating and potentially damaging the battery if not closely monitored.

In summary, using a constant current charger for your lithium ion battery is the recommended and safer method. Charging with a constant voltage, especially without proper monitoring, can potentially damage the battery and affect its overall performance and lifespan. I hope this information helps with your charger circuit.

 

[alphy]

Hello,

Thank you for your question. I can provide you with some information about the difference between constant current and constant voltage charging for Lithium ion batteries.

First, let's understand how a Lithium ion battery is typically charged. When a battery is discharged, the lithium ions move from the negative electrode (anode) to the positive electrode (cathode). During charging, the process is reversed and the ions move back to the anode. This movement of ions is what stores and releases energy in the battery.

Now, onto the difference between constant current and constant voltage charging. Constant current charging means that the current (measured in amps) flowing into the battery remains constant throughout the charging process. This type of charging is typically used in the initial stages of charging when the battery is at a low state of charge. As the battery charges, the voltage increases and the current naturally decreases.

On the other hand, constant voltage charging means that the voltage (measured in volts) applied to the battery remains constant throughout the charging process. This type of charging is typically used in the later stages of charging when the battery is close to reaching its full capacity. In this stage, the current decreases even further until it eventually stops and the battery is fully charged.

So, to answer your question, charging a Lithium ion battery with a constant voltage of 4/4.1 volts may not be sufficient to fully charge the battery. This is because the current will decrease as the battery reaches its full capacity, and if the voltage remains constant, the battery may not receive enough current to reach its full capacity.

In summary, it is important to use a constant current charger for the initial stages of charging a Lithium ion battery, and then switch to a constant voltage charger for the later stages. This will ensure that the battery is fully charged and can operate at its optimal capacity.

I hope this information helps. If you have any further questions, please don't hesitate to ask.

Best,