Hello,
We recently developed a charging circuit to charge a 6Ah 3.7V Li-Ion battery. The goal is to charge it at 3A. We use the BQ25303J in our circuit. The 5V power supply is provided by a 3A USB-C PD charger. Unfortunately as of today we are not able to see more than 1A being pushed in the battery. We are looking for an explanation, please find attached the schematics and the part of PCB board (note that the big via under the ic is filled with solder, for manual assembly. The battery is connected through the JST connector (J7) on the bottom left of the BQ25303J (U8). Inductor L1 ref : https://ds.yuden.co.jp/TYCOMPAS/ut/detail?pn=NRS5024T1R0NMGJV%20&u=M
JP7 is also not mentioned on the schematics but is only used to connect an external open drain output from a fault detection circuitry. It is currently opened and thus has no impact on the studied circuit.TH1 is also connected through the TH1 JST connector, it is a 103-AT-4 thermistor and its value was around 9.4k when doing our testing.
We also measured the traces of the current on our oscilloscope during charge. During this measurement a shunt resistor of 0.22ohm has been used in series with the inductor, with short wires AWG 24 of 1cm (it could have a small impact on the measurement but nothing exagerated).
The power supply itself is not the cause, we even tested once with a laboratory power supply to make sure it was not the bottleneck.
Can you please have a look at this ? Do you see a reason for this behaviour ?
Thanks in advance for your time and help.
Best regards,
Emanuel Arnold Electronics Specialist
in-Terra Switzerland
Schematic:
Current on the coil :
