IP2326 from Injonic is a highly efficient boost converter that takes 5V USB input and boosts it to 8.4 (2S) or 12.6V (3S). It includes balancing for 2S batteries and can charge 2S or 3S batteries from USB power supplies.
Since at its heart it is a boost converter, it may also be used to power 12V devices from 5V USB power (at a maximum of 10-12W).
Overview
IP2326 is a highly efficient synchronous boost converter with a 500kHz switching frequency and a built-in power MOSFET.
The efficiency is 94% at 8V/1A output, and drops slightly to 92% at 1.5A. With its pin CON_SEL, it can be switched from 2S to 3S configuration.
Pin LED connects to an optional charging indicator LED, and BAT_STAT provides a digital signal for the charging state.
The enable pin EN can be pulled to ground to temporarily disable the charger:
| State | Power Consumption |
|---|---|
EN=LOW |
3uA |
EN=HIGH |
20mA |
Input
The charger works most efficiently when the input and output voltage differences are small.
It is a strict boost converter, so the input voltage always needs to be lower than the output voltage. The recommended input voltage range is 4.5-9.5V.
Fast Charge Input
If you connect a USB power source with fast charge capabilities, IP2326 will request higher voltages in these scenarios:
| Battery Voltage | Configuration | Action |
|---|---|---|
| <6.2V | 2S | use 5V |
| <6.8V | 2S | request 5.4V input |
| <7.8V | 2S | request 6V input |
| <7.8V | 2S | request 6V input |
| >7.8V | 2S | request 7V input |
| <9V | 3S | use 5V |
| <10.5V | 3S | request 7V input |
| >10.5V | 3S | request 9V input |
When IP2326 is powered on, it first tests the input power supply for fast charge capabilities. This is why there is a delay of 3-4 seconds before IP2326 starts charging. If the supply does not respond to fast charge protocol requests, IP2326 uses the supplied input voltage as-is.
Over-Current Protection
If the input voltage drops (i.e. due to a weak 5V power source), IP2326 intelligently reduces the output current to prevent overloading the 5V adapter. It also includes over-voltage and shortcut-protections.
Output
IP2326 provides a main output to connect the battery string. Via pin CON_SEL, the output voltage can be adjusted to match LiIon 2S or 3S.
The maximum output current is 1.5A, however this current is limited by the maximum input power (15W). So you may be able to yield 1.5A in 2S configuration, however in 3S configuration it is closer to 1A.
Battery Balancing
In 2S configuration, IP2326 can add battery balancing through a sensing port (VBATM) that measures each of the two battery cell voltages. In 3S configuration, you cannot use balancing and need to add your own balancing BMS.
Slow Balancing
Keep in mind that battery balancing is typically in the milli-Ampere region and designed to equal out small charge imbalances. The balancing current is determined by Rcb (should be >100 Ohm). Icb = Vcb / Rcb.
In typical scenarios the maximum equilibrium current is less than 40mA.
So if you use two batteries with grossly different state of charge, or if you connect different-sized battery packs in series, balancing will work (eventually) but take a long time.
If you i.e. use a fully charged and an empty 18650 battery cell with 2.500mAh capacity, even when balancing is set to its maximum, it would take many days until equilibrium is established.
Fake Schematics
Fake schematics flood the Internet showing IP2326 breakout boards (like LX-LISC) in 3S configuration with balancing. These schematics are wrong and dangerous.
Occasionally you may come across YouTube videos claiming that IP2326 balancing does not work. That’s of course nonsense and often due to user error, either trying to balance 3S configurations, or trying to balance completely different battery cells with grossly different state-of-charge and capacity.
Temperature Protection
The chip monitors its own temperature and turns off when it exceeds 135C.
NTC Probe
An additional 100K NTC thermistor can be connected to monitor the battery pack temperature.
- If no thermistor is used,
NTCis pulled low via a 51K resistor. - If a suitable thermistor is connected, IP2326 sends a 20 µA sensing current and analyzes the voltage drop:
NTC pin voltage |
Action |
|---|---|
| <0.43V | stop charging, high temperature |
| <0.56V | hot battery, reduce charging rate by 50% |
| <1.32V | normal |
| >1.32V | stop charging, freezing |
To enable an external NTC thermistor, the default 51K resistor must be replaced with a resistor that matches the thermistor in use, i.e. 100K thermistor (B=4100) requires a 82K replacement resistor.
Adjustments
IP2326 can be adjusted via external resistors:
| Adjustment | Pin | Default (floating) | Adjustments |
|---|---|---|---|
| CC Current | ISET |
120K-60K= 0.75A-1.5A |
|
| CV Voltage | VSET |
8.4/12.6V | 1K-120K= 8.1/12.3V-8.3/12.5V |
| Charging Voltage Range | CON_SEL |
2S | 1K to GND for 3S |
| Input Undervoltage Threshold | VIN_UVSET |
4.65V | 120K-1K= 4.45-4.25V |
| Input Overvoltage Threshold | VIN_OVSET |
8.75V | 120K-68K= 8.4-8.0V 1K=disabled |
| Charging Timeout | TIME_SET |
24h | 68K=4h 120K=12h 1K=no timeout |
2S / 3S-Charging
CON_SEL |
Mode | Output Voltage |
|---|---|---|
| floating/unconnected | 2S | 6.0-8.2V |
via a 1K resistor to GND |
3S | 9.0-12.4V |
Charging
| Battery Configuration | Dead Battery | Undervoltage | Constant Current (ISET) |
Constant Voltage |
|---|---|---|---|---|
| 2S | <3.7V | <6V | 6.0-8.3V | 8.4V (VSET) |
| 3S | <3.7V | <9V | 9.0-12.5V | 12.6V (VSET) |
| Charging Mode | Charging Current |
|---|---|
| Dead Battery | 50mA |
| Undervoltage | 100mA |
| Constant Current | ISET |
| Constant Voltage | <200mA: pauses 30s, then tests whether stop charging voltage is reached |
If the charger is left connected to the battery after it is fully charged, the charger automatically resumes charging when the battery voltage drops below 8.0V (2S) or 12.0V (3S).
Efficiency
Conversion efficiency is in a range of 91-94%, depending on charging current, voltage difference, and state of charge:
- The higher the voltage difference between input and output, the lower the efficiency.
- The higher the output current, the lower the efficiency.
Even at 5V input and 8.2V/2A (16.4W) and 12.4V/1.2A (14.9W) output, the efficiency remains better than 90%. That is quite remarkable.
With higher input voltages, efficiency raises:
| Input Voltage | Output | Efficiency |
|---|---|---|
| 5V | 12.4V/1.0A | 90.5% |
| 7V | 12.4V/1.0A | 93% |
| 9V | 12.4V/1.0A | 94.5% |
The datasheet provides detailed graphs.
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(content created Aug 17, 2025)