Lithium-ion battery chargers: how do they work

Whether laptops, cell phones, or electric or hybrid cars, you can use lithium-ion technology to power all these devices.

The primary reasons are high energy, recharging capability and lightweight nature.

If you want long life and optimal performance from your lithium-ion batteries, choose the battery charger carefully; for example, use chargers designed explicitly for lithium-ion batteries.

Understanding lithium-ion batteries:

Lithium ions move between positive and negative plates and generate electricity in lithium-ion batteries.

These batteries do not have liquid electrolytes, so they have a tremendous boost over lead-acid batteries.

Lithium-ion batteries vary depending on the size, construction and application.

New technology has been introduced in lithium-ion batteries, which are of lithium ferrous phosphate (LFP or LiFePO4), known as the best battery technology.

How do lithium-ion batteries work?

The lithium-ion batteries have five main components. These are:

  • Cathode
  • Anode
  • Electrolyte
  • Separator
  • Container

All these components have their specific role and work together in each cell to store or emit energy.

Lithium-ion batteries mostly have graphite anode, which holds lithium ions released during charging.

Sometimes, the anode is also made of silicon carbon.

On the contrary, the cathode is made of lithium metal or any lithium-rich material based on the type of lithium cell, including:

  • Lithium Cobalt Oxide or LCO battery
  • Lithium Iron Phosphate LFP or LiFePO4
  • Lithium Manganese Oxide or LMO battery
  • Lithium Nickel Manganese Cobalt Oxide or NMC battery

As the batteries are named after cathode, you can understand how vital cathodes are in lithium-ion batteries.

Let’s read about their role.

During charging: At this stage, the lithium-ion cathode emits positive lithium ions, reaching the anode after traveling through the electrolyte and the separator.

On the other hand, the free electrons released by the lithium ions travel to the anode through the device’s external medium.

During discharging: At this time, the cathode returns the released li ions and electrons from the anode plate.

The charging and discharging of li-ion batteries help transfer lithium ions across the two electrodes.

On the other hand, the separator blocks the free electrons’ movement across the electrodes through the electrolyte.

Further, it helps prevent short circuits if electrolyte evaporates by chance.

The last component, i.e., case or container, securely holds all the above components in a single unit.

Also, the inner components remain insulated and protected from outer influences in the case.

li-ion batteries for e-bike

li-ion batteries for e-bike

How to charge a lithium-ion battery?

There are three types of lithium-ion battery chargers you can use.

Use a power outlet and a compatible AC to DC battery charger:

One of the best lithium ferrous phosphate solar battery chargers is the 12V 20A AV-to-DC LFP Portable battery charger.

You can use it to refill the battery’s charge and to reactivate your li-ion battery shut down by the BMS (battery management system).

Use solar panels and a compatible MPPT charge controller:

Suppose you want to charge your LiFePO4 batteries with a solar panel; use MPPT charge controllers designed explicitly for LFP batteries only.

In that case, a few examples are Rover 60 Amperes MPPT solar charge controller, Rego 12 Volts 60 MPPT charge controller, and other similar MPPT charge controllers.

Using your RV’s or car’s alternator and a compatible Dc to DC onboard battery charger.

You can charge your lithium-ion battery through the vehicle’s alternator in two ways:

  • Using a Dc to DC onboard battery charger: you must prioritize using an onboard battery charger because it charges your house batteries first instead of a starter battery.
  • Using a Dc to DC MPPT charge controller: if you have installed solar panels, use a 12V 30A dual input Dc-Dc onboard battery charger with MPPT, as it not only acts as a power source but also refills your house batteries in no time.
Charging li-ion batteries

Charging li-ion batteries

Can I use a standard charger to charge a lithium-ion battery?

Then, can you use a  lead-acid battery charger to charge the lithium-ion battery?

How do battery chargers work?

The voltage of the lithium batteries is higher than the lead acid batteries with similar specifications.

Also, these batteries have a narrow window for operating voltage.

During charging, lithium-ion batteries receive a continuous flow of current, and once they are fully charged, they cut off automatically.

You will not experience any trickle or float charge with a lithium-ion battery charger.

Further, a lithium-ion battery charger works best during fast charging.

Such chargers supply current rapidly until the battery’s charge becomes full and reduces the charge in the end as the battery becomes full.

On the other hand, lead acid battery chargers follow three steps during charging.

These are 

  • Bulk
  • Absorption
  • Float

In the bulk phase, the battery receives charge faster until it reaches an 80 percent charged state.

At this stage, the battery’s internal resistance does not accept charging at such a fast rate.

Thus, it becomes slower, and the battery goes into an absorption stage.

Finally, the float stage comes when the current received by the battery reaches the trickle stage, or the charger remains in the absorption stage for four hours.

It mainly happens when the charger needs to be better for the battery if it has charged many batteries simultaneously.

Several SMART chargers can test the battery before charging and determine which stage to begin.

As a result, the battery is charged much faster and remains protected from damage.

Is using the wrong type of battery charger safe?

If you use a  lithium-ion battery charger for a lead acid battery, it can charge it for as long as it provides constant voltage; however, it may damage the battery over time if you can control the voltage and the charging time.

If you can’t control this, using a lithium battery charger with a lead-acid battery is not advisable.

On the other hand, use a lead-acid battery charger for a lithium-ion battery if the charger is set at a maximum voltage and its automatic equalization mode is disabled.

If this feature is turned off, it is safe to use the lead-acid charger for li-ion batteries; however, you must turn off the battery as soon as it gets fully charged.

Using the correct charger for its specific battery type is always recommended.

You can also use multi-mode chargers to charge any battery and protect and prolong its life.

AC to DC battery chargers

AC to DC battery chargers

Charging your lithium-ion batteries: expert tips for a longer lifespan

Remember these tips and suggestions when you charge or discharge lithium-ion batteries to extend the battery’s life.

Respect a CCCV charging process, especially during the floating mode:

Always pick a specific charger for charging your lithium-ion batteries. Lithium-ion batteries get charged in two steps.

Firstly, it is Constant current charging; here, current is applied until the battery reaches its end-of-charge voltage level.

After this, the constant voltage (CV) process starts, wherein the current decreases when the battery becomes full.

The battery capacity depends on the end-of-the-charge voltage, so the battery capacity will also reduce if you use a lower voltage.

Don’t leave the battery permanently charged in the floating current mode that starts after the CV mode.

Be mindful of the temperatures at which the battery is being charged: 

A battery gets primarily affected by the temperature it is operating.

At extremely high temperatures, the electrolyte expands too much and has no optimal shape to allow the free exchange of lithium ions.

On the contrary, in extremely low temperatures, the electrodes contract, making extracting the ions difficult.

Further, the conductivity of the electrolyte also decreases, leading to slow movement of ions.

Thus, try to maintain optimal temperature while the battery is in use.

Favorite a partial depth of discharge (DoD)

A battery’s complete charging or discharging cycle is called its depth of discharge, i.e., where 100% of the energy stored is delivered as output. A 65% DOD means that 65% of the battery’s full capacity is delivered, while 35% is in reverse.

Repeated charging and full discharging, i.e., 100% DoD, lessen the battery’s cycle life.

The battery faces stress in both states of full charge and discharge, and such repeated encounters lead to its faster aging.

By restricting the li-ion battery’s DoD in the intended application, one can increase the number of cycles of that battery to a great extent.

Lower your charging C rate:

The speed of charging and discharging a battery relative to its capacity is called its C rate. 1 C rate of a battery shows that the rated discharge current shall remove the battery in one hour.

We can calculate the C rate of any battery by dividing the charge/discharge current in amps by the battery’s capacity in Amp-hrs.

When a battery is charged or discharged at higher C rates, the total amount of energy stored/produced reduces drastically due to increased internal loss in heat, which is proportional to charge/discharge current.

Secondly,m at lower C rates such as C/2 or C/5, Li-ions have enough time to intercalate themselves in Graphite sheets properly.

With the increase in C-rate, this intercalation becomes harder and harder.

Li-ions start depositing on the surface of Graphite electrodes rather than penetrating. It leads to faster aging of the battery.

Depending upon the application time available for the intended use of a Li-ion battery, a proper balance between the C-rate and aging of the battery has to be decided.

Keeping the charging/discharging current near the manufacturer-recommended C rate is better.

li-ion batteries for laptops

li-ion batteries for laptops


Battery cables also play a significant role in the functioning of the chargers.

So, if you need help, contact Cloom, as we manufacture superior cable assemblies and wiring harnesses.