BQ27510-G3: Cannot get accurate Average Current or Instantaneous Current value

Robert Helvestine

Part Number: BQ27510-G3
Other Parts Discussed in Thread: BQSTUDIO

Hello. I'm trying to read the battery current using Average Current (address 0x14 and 0x15) and Instantaneous Current (address 0x22 and 0x23). While testing, my battery is drawing ~40mA as verified using a DMM in series. The Technical Reference Manual says that what is returned is a "signed integer value", and the units are mA. I take this to mean a 32 bit value. The bytes returned are the following:

0xd6

0xff

0x00

0xd6 is 214 decimal, nowhere near 40. If you change the most significant bit from a 1 to a 0 (1 signifying current exiting the battery), this value is now 0x56 or decimal 86, again not near 40. Incorporating the other bytes only makes the value larger. Can someone elaborate as to how to get an accurate current reading?

Thanks,

Rob

over 6 years ago

0 Onyx Ahiakwo over 6 years ago

TI__Guru* 76230 points

hi Rob

Can you make sure the device is not sealed. Then you send command 0x14 and then read back two bytes. The data will return in little endian format.

In the example below voltage was 3620 mV, and was read with bqstudio

24 0E in little endian is 0E 24 which is 3620 in decimal. Pls do the same for current. i hope this helps

thanks

Onyx

0 Robert Helvestine over 6 years ago in reply to Onyx Ahiakwo

Intellectual 275 points

Thanks Onyx. However, I'm not having any problem reading battery voltage (that is accurate). I'm having an issue reading battery current. If I can successfully read battery voltage, I assume the part is not sealed. When I read battery Average Current (addresses 0x14 and 0x15), the two bytes I receive are 0xd6 and 0xff. 0xd6ff is 55039 in decimal. The units (according to the datasheet) is mA, so this doesn't make sense. Can you show a screenshot of BQstudio reading battery current?

0 Onyx Ahiakwo over 6 years ago in reply to Robert Helvestine

TI__Guru* 76230 points

Robert
Current is a signed integer so you will have to do the signed 2's complement. So d6 ff which is little endian for ffd6 will convert to -42.

calculator below:
www.rapidtables.com/.../hex-to-decimal.html
thanks
Onyx

0 Robert Helvestine over 6 years ago in reply to Onyx Ahiakwo

Intellectual 275 points

Thank you Onyx!

Power management

Power management forum

BQ27510-G3: Cannot get accurate Average Current or Instantaneous Current value