Hello,
We are currently working on MAX17320G20+T based circuit for cell protection and fuel gauge of a 2 cell series LiPo battery. I've made a arduino library to read/write registers via I2C and able to get the fuel gauge registers working (BATT, PKP, VCELL, CELL1, CELL2 etc.).
But now I'm trying to implement the battery balancing function of the IC. The cell balancing is not happening.
We are enabling the zener for cell balancing with 80mV difference but the higher voltage cell is not going down. We have connected a small load too (LED) at the circuit output. Both cells are draining in the proportional way.
Cell 1 voltage = 3.5V
Cell 2 voltage = 3.9V
So ideally Cell 2 voltage should be 3.58 to 3.6V via the zener drop if the balancing is happening.
But nothing is happening.
Schematic and test code is attached
#include <Wire.h>
#include "MAX17320.h"
//uint8_t r_sense = 1;
void setup() {
Wire.begin(DEVICE_ADDRESS);
Wire.begin(NVM_ADDRESS);
Serial.begin(9600);
}
void loop() {
// read_cell1();
delay(1000);
// Serial.println(MAX17320::read_cell1());
MAX17320::set_cell_balancing(ZenerEnable, mV800, 11.7, 100);
}Function call
void set_cell_balancing(BatteryBalancingZener zener_enable, CellBalancingConfig bal_cfg, float r_mismatch, uint8_t imbalance)
{
r_mismatch = 32 * r_mismatch / 125;
uint16_t RMismatch = round(r_mismatch) << 5;
imbalance = round(imbalance / 10);
if (imbalance <= 31 && r_mismatch <= 31)
{
uint16_t code = zener_enable | static_cast<uint16_t>(bal_cfg) | static_cast<uint16_t>(RMismatch) | static_cast<uint16_t>(imbalance);
unlock_write_protection();
write_named_register_nvm(RegisterNvm::NBalTh, code);
lock_write_protection();
}
}Cell balancing function
enum BatteryBalancingZener
{
ZenerDisable = 0,
ZenerEnable = 1 << 13,
};
enum CellBalancingConfig
{
Disable = 0,
/// For 2.5mV
mV25 = 1 << 10,
/// For 5mV
mV50 = 2 << 10,
/// For 10mV
mV100 = 3 << 10,
/// For 20mV
mV200 = 4 << 10,
/// For 40mV
mV400 = 5 << 10,
/// For 80mV
mV800 = 6 << 10,
/// For 160mV
mV1600 = 7 << 10,
};config file
Ref : Datashet : https://www.analog.com/media/en/technical-documentation/data-sheets/MAX17320.pdf (Page 70, Battery Balancing section)
Pls suggest a solution for this. And let us know if you need more information on the test results.
Best regards
