Hi team,
The phenomenon:
1. The device cannot turn on and the battery is fully charged in a low temperature (10°C) environment.
2. The charge through the bq27520 is 0 and the temperature is 3 degrees.
3. Scope: Jiangxi province, Jiangsu province, etc. and the most of the Chinese provinces.
Issue: the problem is in the fuel gauge. Batteries, external NTC resistors, etc. are excluded. And the power count data is analyzed in the following table:
| Turn on the wire brush | Do not turn on the wire brush | |
| Low temperature -10°, external NTC resistance | 27K | 25K |
| Low temperature LK log temperature | -9.2 | 26~27 |
| The low-temperature battery charge corresponds to the power-on condition | 90% on, 60% on | 90%, no power on; 60% no power on |
| Normal temperature, external NTC resistor value | 10K | 11K |
| The fuel gauge TS pin (on the board) is to ground | 11K | 11K |
| Single-chip TS pin to ground impedance | 3M | 3M |
| Power on | 90% corresponds to 90% | 90% corresponds to 45% |
| 4.1-V battery, 90% charge, normal temperature performance | NTC 12.9K, power on, TS voltage 0.9 V high pulse | NTC 12.9K, no power on, TS voltage 0.9-V high pulse |
As can be seen from the table above： devices that do not turn on at a low temperature do not have the right values for temperature acquisition at a low temperature, do not display the power level, and do not turn on at full charge.
Circuit diagram：
Could you please help check this case?
Thanks!
Best Regards,
Cherry
