BU-414: How do Charger Chips Work?

Examine the difference between a charger chip and a microcontroller.

When first introduced in the 1980s, charger chips simplified the design of NiCd and NiMH chargers as batteries with these chemistries were difficult to charge. Li-ion is simpler and most modern charging chips also include the protection circuits that are needed to safe charge Li-ion. These include current and voltage regulation, FET switches and may also contain charge status indicators and cell balancing. Added to most chips is a time-out-timer that halts charge if predictable symptoms do not occur as expected when charging a flawed battery.

Advanced chips also feature pre-charge conditioning (boost) to wake up an inactive battery, as well as a sleep mode that lowers the housekeeping current of the circuit while the battery is in storage. Some chips also initiate a charge if a parasitic load lowers the battery voltage below a preset threshold while residing in a charger.

Although charger chips are easy and economical to use, they have limitations. Most offer a fixed charge algorithm that does not permit fine-tuning for specialty uses. Chips are made for a given battery and may not accommodate different chemistries as requested by the user or read a battery code that may be embedded in a battery holder. Nor do most chips adjust to an optimal charge current when charging an aging battery with reduced charge acceptance.

Microcontrollers offer an alternative to charger chips. Although the design cost is higher because of the extra programming time needed, manufacturing costs are compatible to charger chips. It should be noted that the charge chip or the microcontroller only form a small part of the charger circuit; the bulk of the cost lies in the peripheral components, which include solid-state switches, signal lights and the power supply. The parts cost is directly related to wattage.

Factory-configured charger modules are available that are set to the correct voltage, current and algorithm. Some have seamless DC-DC conversion to allow charging a battery with a higher voltage than the input provides. Options include SMBus, solar charging, discharge for calibration and display. Using soft-programmable charger modules resembles the ready-made AC power supplies that became popular in the 1990s as a lower-cost alternative to building one’s own charger for each application.

Last updated 2016-02-25

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Comments (8)

On February 20, 2012 at 8:31am
Asadullah wrote:

plz tell me how much resistance is required to converts volts from high voltage to low voltage.

On February 20, 2012 at 11:12am
ResistorGuru wrote:

The answer is 2GHz.

But you might want to check out this site if you want to verify the answer: http://en.wikipedia.org/wiki/Voltage_divider…

On January 28, 2014 at 8:25am
mathavan wrote:

how to create charger with help of flyback converter without current feedback

On February 6, 2014 at 4:11pm
Alexis Pomares wrote:

Very good site. Could you comment something about some charger chips references? I mean in your so good style (referring to chemistry type, including advantages, limitations, etc).

On June 4, 2014 at 6:18am
George Mountcastle wrote:

I am making a device where I am using LI-ion batteries in a 6v pack and a 12v pack.  The 6v pack consists of 2 batteries in series and 5 of these sets in parallel. The 12 volt pack is 4 batteries in series with two sets in parallel.  The battery type is a CR123.  Does anyone make a charger or do i need to make my own?\

Please verify what I have read to be correct the max V is 4.2v/cell and current to be 1 amp.

On August 17, 2014 at 4:42am
Dave wrote:

I am making a charger which can charge 3 cell of Ni-MH cell in series and single cell Li-Ion battery, the charge algorithms should be different. Could you help how to determinate the battery type?

On June 17, 2015 at 7:23pm
Jes wrote:

any chips or MCU chip you can recommend that detects the off-the-shelf rechargeable batteries, which is the right batteries for the charging job but the user accidentally forgot to replace the non-rechargeable batteries he inserted during his trip and he plug in to recharge. Never heard of a news exploding non-rechargeable battery that were recharge but I guess the worst scenario the alkaline will leak.

I mean, any info of a chip that can detect the battery isn’t rechargeable?

On November 30, 2017 at 12:27pm
Kim wrote:

I’m a beginner and I’m dealing with zebra batteries for RW series printer. I still don’t understand the chip charger and the protection circuit. What happens if I try to recharge battery cells applying 5v on them without the circuit? It could explode? It can be done with a lower voltage? Is it even possible? I have two cells of CGR18650AF 3.6v and 2050 mah and two cells of ISR 18650 3.7v 2500mah.
I’m working to replace 4 battery cells and I would like to know more about them and if these two pairs can work together. I also tried soldering 4 of the CGR18650AF on the protection circuit and it didn’t charge anymore, I’m afraid I screwed it. I don’t understand what’s going on. What should I to do to fix these batteries?