Full charge flag and remaining capacity problem on BQ34Z100-G1

Dear Team,

could you please help this customer?

Thanks a lot in advance for your help.


Best regards,
Massimiliano De Cristofaro
Application Support Engineer - Power Management
ASKTEXAS DiamondLane – EMEA Distribution Support
Texas Instruments Deutschland

Corentin,
Analyzing NiMH charge termination can be difficult. I could see where it reached deltaT based charge termination in one file, but I did not see charge termination in the others. The capacity variations may be affected by the Voltage Consistency Check. I would try disabling VconsEn and enable FConvEn to help gauging accuracy near the end of discharge.
Tom

Thank you for your response.



In chargetoppingtrickleBQ.log, I see charge termination because FC flag is set in sample 2123. There is a problem here because, the value in BQ34Z100-G1 are 0.8°C for NiMH Delta Temp and 240 secondes for NiMH Delta Temp Time, but the flag is set when there is a rising of 1.1°C in 240 seconds it is not in accordance with 0.8°C/4min.

There is another problem in this log, the capacity drop at the charge termination and come back at the end of discharge. It is a big error, BQ34Z100-G1 says the battery has a capacity of 1Ah, while it has a capacity of 6Ah.



In Csur20chargedecharge.log, there is not charge termination in the first charge, because the current charge is too low. So the battery is in overcharge and TrueRC continues to rise. There is three problems. When the discharge begin, the capacity fall and the soc stay at 100% for 5 hours because Remaining Cap wait to be equals to TrueRC, to decrease. When the battery is almost empty, BQ34Z100-G1 says SOC is equals to 19%.
At the end of this log I see a new fall of capacity during a new charge. In this new charge, there is a charge termination at sample 113789 and it is an error because the condition of "DeltaT" and "-DV" are not respect. The value for DeltaT condition are the same as in chargetoppingtrickleBQ.log. There is a problem because the flag is set when there is a rising of 0.2°C in 240 seconds. For this charge NiMH Cell Negative Delta Volt was equals to 2 mV and NiMH Cell Negative Delta Time was equals, so it is a slope of 0.5mV/min/cell. When the FC flag is set, tension decrease of 0.07mV/min/cell


In test12Atambiante.log, there is a charge termination at sample 2192, the value for DeltaT condition are the same as in chargetoppingtrickleBQ.log and there is the same problem because the flag is set when there is a rising of 1.0°C in 240 seconds, it is not in accordance with 0.8°C/4min.

The big problems here are the drop of capacity during discharge, SOC equals 0 too early and the drop of capacity when OCV arrived . The FCC equals 4,5Ah after a discharge of 5,5Ah, the error is bigger than 1Ah.



In test2Atamb.log, there is a charge termination at sample 2187, the value for DeltaT condition are the same as in last logs and there is the same problem because the flag is set when there is a rising of 1.1°C in 240 seconds (not in accordance with 0.8°C/4min). Another problem arrived with the OCV, the capacity drop again while the last value was good.


Today, I have 3 important problems :

- charge termination do not arrive in accordance with 0.8°C/4min.
- capacity have big jump (particulary with OCV, charge termination, or fast discharge)

- bad management of overcharge with topping/trickle charge



I would apply your advice about VconsEn and FConvEn but I have a question. Should I have VconsEn and FConvEn enable or disable during a learning cycle ?

Hi Tom,

Could you please help this customer?

Thanks a lot in advance for your support!

Best regards,
Massimiliano De Cristofaro
Application Support Engineer - Power Management
ASKTEXAS DiamondLane – EMEA Distribution Support
Texas Instruments Deutschland

I reviewed the data again and I would recommended setting the NiMH charge termination parameters to their default values and disable NiMH voltage based charge termination to verify that the temperature based charge termination is being met. I would disable VconsEn and FConvEn and also allow the pack to rest long enough for the OCVTAKEN flag to set in the rest period after charge and discharge. Gauging looked good for the 2A discharge case, but SOC reached 0 early in the 12A case. We may have to tailor the Ra table for a better fit to the typical discharge current.

Thanks for your help, now the gas gauge is better.

I set the NiMH charge termination parameters to their default values and disable NiMH voltage. There is a problem with default parameters for (ΔT/Δt) that stop battery at 1.0°C/min, our batteries can't reach this limit; you can see it in the newvalue061016.log the maximum is 0.8°C/min with an important overcharge.

I disable FConEn (and VconsEn) that permit to have better data from gas gauge.

Is it possible to have more information about these two flags (VconEn : : Enable voltage measurement consistency check, FConEn : Enable fast convergence algorithm) ? Why is it important to disable it ?

In the last reply you say that the 2A discharge case was good for you.

I think the 2A discharge case was not so good because :

-30 minutes after the begin of the charge, SOC and remaining capacity are equals to 0

-90 minutes after a discharge of 5800 mAh, Full Charge Capacity is equals to 4491 mAh.

I sent the cells, datasheet and complete Cell Characterization Request for a cell's characterization. You received all on Wednesday, October 12, 2016. 

Now, gas gauge is better at room temperature and at 50°C as you can see in toppingtrickle.log and in essai2 50.log but there are always problems at low temperature. You can see it in essai5degré2.log.
The problems are the following :

-At the start of the charge, the battery is empty but when the charge begin there is a jump of SOC (20 %) and remaining capacity (1014 mAh).

-During charge, True RC go to 8500 mAh, despite the battery capacity of 5000 mAh for this temperature. If I had discharged it just after the end of charge, SOC was equal to 100 %, for the first part of discharge of 3500 mAh. At the end there would have been an important drop of 70 %.

To do not have this problem I wait an OCV after it the data was good so I make the discharge, that was always good, I wait a new OCV and there are problem with it.

-After the OCV whose follow the discharge, True RC is equals to 4039 mAh while the battery is empty. When I begin charge, remaining capacity is equals to 4039 mAh and the SOC to 79%.

-I make a new discharge of 5 minutes to have voltage equals to Terminate Voltage and set remaining capacity to 0, Full Charge Capacity drop to 1281 mAh.

Can these problems be resolved by characterization of my cells ? Is the characterization made ?

ARTS-Energy251016.zip