HCX-D167 LiFePO4 BMS strange behavior

Batteries, Chargers, and Battery Management Systems.
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rainman_v84   1 µW

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HCX-D167 LiFePO4 BMS strange behavior

Post by rainman_v84 » Apr 12 2015 6:49am

Hi everyone,
I've recently upgraded my LiFePO4 battery to 20s and used an HCX-D167 BMS.
As per supplier instructions, I've first charged the battery through the BMS and then manually balanced each cell to 3.65V.
Then I've made a test run, and found the battery capacity to be twice lower than it should have been.
I've made some measurements and found some strange BMS behavior - if I measure voltages immediately on balance leads, every cell reads as 3.3V.
However if I measure voltages above the balance resistors (see the picture) all the cells read the same 3.3V except 2 cells - 1 reads 3.7V and another reads 2.7V. So, the BMS thinks that the 2.7V cell is drained and shuts the whole battery down.
Also, when I measured the voltage drop on the resistors, there is no drop on them except two - lines 3 and 4 (~0.5V).

Does anyone know how to fix this problem?
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BMS_photo.jpg

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agniusm   10 MW

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Re: HCX-D167 LiFePO4 BMS strange behavior

Post by agniusm » Apr 13 2015 2:35am

Connect your charger and leave it for 48 hours. Then check back. Measure your cells on balancing connector before and after

rainman_v84   1 µW

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Re: HCX-D167 LiFePO4 BMS strange behavior

Post by rainman_v84 » Apr 26 2015 9:11am

I've tried leaving the battery connected to a charger for 48 hours, and have again obtained an unbalanced battery with weird readings on the same channels that were faulty before.
I have measured the resistance between the leads of all the elements located after the balance resistors and found that 2 elements marked AFTV(1X) have different resistance between their leads.
What kind of elements are those? I could not find them in any database.
BMS_4.jpg

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