BQ34Z100-G1: BQ34z100-g1. Cell termination voltage

Gorka Lorea

Expert 1620 points

Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ34Z100

Hi,

I am using a BQ34z100-g1 with an 8s2p LiFePO4 batteries. I have one doubt about the Cell Termination Voltage.

¿What are the condictions that mus be met in the BQ for the SoC to go to 0%?

I have done two tests:

- Discharge the battery from 100% to this voltage (Cell Termination Voltage x 8 (number of cells)). Then the SoC falls to 0% (regardless of the SoC it had before reach this point)

- With battery at a high SoC(for example 70%) quit the battery (but not quit the BQ34z100-g1 power supply). Then the BQ shows voltage of 0mV but the SoC remains at 70%.

Is there any current consideration in addition to the Cell Voltage Termination that must be met for the SoC to go to 0%?

Best regards,

over 5 years ago

0 Bryan Kahler over 5 years ago

TI__Mastermind 25955 points

Hi Gorka,

The first test sounds successful. If this isn't the case, please tell me what value you expect. Are you seeing a hard drop? If so, from what % to 0%?

If you like the fall to be gradual, please enable SMOOTHing in the gauge. The device will update capacity.

When the quit the battery, is it still connected and giving a voltage to the gauge, or has it been disconnected from the circuit and is therefore contributing 0 V to the system? If the battery is physically disconnected, the gauge will lose the capacity estimate and a simulation will need to be run after the battery is connected once more. To force the simulation, please issue a reset command to the gauge. The SOC estimation may include some error as it is based on the OCV, but will be corrected with cycling of the cell.

Sincerely,
Bryan Kahler

0 Gorka Lorea over 5 years ago in reply to Bryan Kahler

Expert 1620 points

Hi Bryan,

The first test is what I expected. Going to 0% when Cell Termination Voltage is reached.

The second test is what I do not understand. I quit the battery but maintain the supply of the bq34z100-g1 so the bq34z100 is reading 0mV of battery voltage (obviously this voltage is < Cell Termination Voltage). However, although Cell Termination Voltage has been reached the SoC does not go to 0%.

Why is happening this? why is the SoC not going to 0% if the battery voltage is < Cell Termination Voltage?

Best regards,

0 Bryan Kahler over 5 years ago in reply to Gorka Lorea

TI__Mastermind 25955 points

Hi Gorka,

I apologize, I believe something is being lost in translation with the word 'quit'.

When you quit the battery, are you disconnecting the battery from the gauge while still powering the gauge with some other voltage rail?

If so, how long do you leave the battery disconnected?

Is the device under load when the battery is removed?

Do you have a gauge settings file (gg.csv) and a log file of the event that we may review? Thanks!

Sincerely,
Bryan Kahler

0 Gorka Lorea over 5 years ago in reply to Bryan Kahler

Expert 1620 points

Hi Bryan,

Here you have the log

6327.BQ_LiFEPO4.log

Data Log

TimeStamp,Voltage,Current,Temperature,State Of Charge,Max Error,Full Charge Capacity,Remaining Capacity,Cycle Count,State Of Health,
2018-05-28 03:01:35,28128,-14,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:38,28128,-13,24.1,100,1,6557,6552,1,100,
2018-05-28 03:01:39,28128,-14,24.1,100,1,6557,6552,1,100,
2018-05-28 03:01:42,28128,-13,24.1,100,1,6557,6552,1,100,
2018-05-28 03:01:43,28128,-17,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:46,28128,-19,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:47,28136,-18,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:50,28128,-18,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:51,28136,-18,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:54,28128,-18,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:55,28128,-18,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:58,28128,-13,24.0,100,1,6557,6552,1,100,
2018-05-28 03:01:59,28128,-13,24.0,100,1,6557,6552,1,100,
2018-05-28 03:02:02,28136,-13,24.0,100,1,6557,6552,1,100,
2018-05-28 03:02:03,28128,-13,24.0,100,1,6557,6552,1,100,
2018-05-28 03:02:06,28136,-13,24.0,100,1,6557,6552,1,100,
2018-05-28 03:02:07,28136,-13,24.0,100,1,6557,6552,1,100,
2018-05-28 03:02:10,28136,-13,24.0,100,1,6557,6552,1,100,
2018-05-28 03:02:11,28128,-13,24.0,100,1,6557,6552,1,100,
2018-05-28 03:02:14,28136,-12,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:15,28136,-12,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:18,28136,-14,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:19,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:22,28128,-14,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:23,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:28,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:31,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:34,28128,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:35,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:38,28128,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:39,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:42,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:43,28128,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:46,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:47,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:50,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:51,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:54,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:55,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:58,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:02:59,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:02,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:03,28136,-14,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:06,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:07,28128,-14,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:10,28128,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:11,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:14,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:15,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:18,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:19,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:22,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:23,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:26,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:27,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:30,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:31,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:34,28136,-12,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:35,28136,-12,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:38,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:39,28128,-14,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:42,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:43,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:46,28136,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:47,28136,-19,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:52,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:54,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:55,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:58,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:03:59,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:02,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:03,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:06,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:07,28128,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:10,28136,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:11,64,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:14,32,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:15,24,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:18,16,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:19,16,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:22,8,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:23,8,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:26,8,-15,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:27,8,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:30,8,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:31,8,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:34,8,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:35,8,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:38,8,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:39,8,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:42,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:43,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:46,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:47,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:50,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:51,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:54,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:55,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:04:58,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:00,0,-14,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:02,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:03,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:06,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:07,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:10,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:11,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:14,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:15,0,-13,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:18,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:19,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:22,0,-13,24.0,100,1,6557,6551,1,100,
2018-05-28 03:05:23,0,-13,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:26,0,-13,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:27,0,-13,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:30,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:31,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:34,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:35,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:40,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:42,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:43,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:46,0,-5,24.1,100,0,6557,6551,1,100,
2018-05-28 03:05:51,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:54,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:55,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:58,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:05:59,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:02,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:03,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:06,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:07,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:10,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:11,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:14,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:15,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:18,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:19,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:23,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:23,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:26,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:27,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:30,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:31,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:34,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:35,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:38,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:39,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:42,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:43,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:46,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:47,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:50,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:51,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:54,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:55,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:58,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:06:59,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:02,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:03,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:06,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:07,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:10,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:11,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:14,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:15,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:18,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:19,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:22,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:23,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:26,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:27,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:32,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:34,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:35,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:38,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:39,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:42,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:43,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:46,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:47,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:50,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:51,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:54,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:55,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:58,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:07:59,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:02,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:03,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:06,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:07,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:12,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:14,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:15,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:18,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:19,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:22,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:23,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:26,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:28,0,-6,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:30,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:31,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:34,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:35,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:38,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:39,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:42,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:43,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:46,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:47,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:50,0,-5,24.1,100,1,6557,6551,1,100,
2018-05-28 03:08:51,0,-6,24.1,100,1,6557,6550,1,100,
2018-05-28 03:08:55,0,-5,24.1,100,1,6557,6550,1,100,
2018-05-28 03:08:55,0,-5,24.1,100,1,6557,6550,1,100,
2018-05-28 03:08:58,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:08:59,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:02,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:03,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:06,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:07,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:10,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:11,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:14,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:15,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:18,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:19,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:24,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:26,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:27,0,-5,24.0,100,1,6557,6550,1,100,
2018-05-28 03:09:30,0,-5,24.0,100,1,6557,6550,1,100,

You can see how battery voltage falls from 28136 mV to 0 mV (< Cell Termination Voltage) but the SoC remains at 100%.

When you quit the battery, are you disconnecting the battery from the gauge while still powering the gauge with some other voltage rail? Yes.

I have left the battery more than an hour in this state and the SoC does not drop to 0%.

Here you have also the gauge setting file

IED_LiFePO4.gg.rar

Best regards,

0 Bryan Kahler over 5 years ago in reply to Gorka Lorea

TI__Mastermind 25955 points

Hi Gorkea,

Thank you for the files. After analysis of the logs:

To immediately have the gauge update SOC to be 0% upon removal of the battery, please reset the gauge either via HW or command.

Otherwise, the gauge will update in up to 5 hours or when a temperature threshold is crossed.

Sincerely,
Bryan Kahler

0 Gorka Lorea over 5 years ago in reply to Bryan Kahler

Expert 1620 points

Hi again Bryan,

I do not want to update SoC to be 0%, I just wanted to know why in test 1 SoC falls to 0% and in test 2 it does not happen.

In accordance to bq34z100 datasheet, SoC should drops to 0% when reaching Cell termination Voltage. It happens in test 1 but it does not happen in test 2.

I just wanted to know why is bq34z100 is behaving in different ways.

Best regards,

0 Bryan Kahler over 5 years ago in reply to Gorka Lorea

TI__Mastermind 25955 points

Hi Gorka,

Thank you for the clarification.

For test #1:

Yes, by discharging in test 1 to termination voltage, the gauge is able to update FCC, RemCap and SOC (over time) during the discharge of the cell to the cell termination voltage (and thereby determine the capacity of the cell), with a net result of 0% SOC upon reaching the cell termination voltage (0% capacity left).

For test #2

When removing the battery, as shown in the logs sent, RemCap does not change appreciably, FCC remain at 100% and therefore SOC does not change. The net result when removing the battery, even though the voltage is now 0 mV, is 100% SOC. The gauge has not been able to coloumb count the discharge and update RemCap, FCC and SOC. RemCap x 100 / FCC = SOC

For more information on the IT gauging algorithm, with respect to the calculation of SOC, please refer to Section 2.7 Update of RemCap and StateOfCharge Values in this app note: www.ti.com/.../slua450

Sincerely,
Bryan Kahler

Power management

Power management forum

BQ34Z100-G1: BQ34z100-g1. Cell termination voltage