Dear Sir,
Using MC33771B driver in our BMS board calculated using coulomb count method.
Case 1, constant current source, I = 0.1A
average Isense value = 241510817 / 28443 / 0.1ohm = 84.9 mA
"ISENSE : 101 mA" & "average Isense : 84.9 mA " , the data does not match !
Case 2, constant current source, I = 1A
average Isense value = 134598805 / 1609 / 0.1ohm = 836 mA
Best regards.
Dear William,
please try to use the formula from the section 9.15 in the MC33771B datasheet.
If the result is still incorrect, please conduct the Current measurement diagnostics described in the section 9.14 in the MC33771 datasheet.
With Best Regards,
Jozef
Hi Jozef,
Thanks for the reply.
We are using "sw499711 MC33771BMC33772B-Battery-Cell-Controllers" for "Monitoring_Diagnostics Examples".
We are observing log for this output like image below.
Multimeter (1.01A) and MC33771 (ISENSE : 1003mA) is consistency, but i am getting Coulomb Count measurement result as 134598805.
What is the relationship between COULOMB_CNT with ISENSE?
How to calculate values?
Average Isense = COULOMB_CNT * V2RES / CC_NB_SAMPLES / RSHUNT !!!
Thanks,
WJ
Hi William,
please check if the FAULT pin is activated. The coulomb count value is impacted if the overflow occurs. I suspect this is the reason for incorrect current result.
In the event an overflow occurs in either COULOMB_CNT or CC_NB_SAMPLES, the
CC_OVR_FLT bit is set and, when unmasked, the FAULT pin is activated. The coulomb
count value is impacted by conversions performed during diagnosis of the current
measurement chain.
The COULOMB_CNT is an integer whose associated resolution is V2RES, therefore,
COULOMB_CNT·V2RES gives μV. If the shunt resistance RSHUNT is expressed in μΩ,
then COULOMB_CNT·V2RES / RSHUNT gives μA.
With Best Regards,
Jozef
