BQ34110: Learning load parameters

Michael Schulze

Part Number: BQ34110

We plan to use the bq34110 in a high capacity/ high cell count application: 6...12 NiMH cells/ 6...30Ah. Because the maximum power dissipation of the learning load is limited in this application we are looking for the lowest discharge current usable in the learning phase to 1..2% discharge the battery. In the datasheet I only found C/100...C/10 as a general recommendation, but how to determine the optimum value for a certain battery pack?

Another question I have: because in our application the BMS system has to support several types of battery packs it is necessary to adjust the learning load resistance according to the pack type. Is it possible to do it by using a PWM modulated fixed resistor load? And if yes, what the optimum PWM frequency range would be?

over 6 years ago

0 Bryan Kahler over 6 years ago

TI__Mastermind 25955 points

Hi Michael,

With respect to the sizing the learning load, please review the following training videos, with extra focus on the end service determination algorithm video linked below.

training.ti.com/overview-bq34110-rarely-discharged-battery-applications-introduction
training.ti.com/bq34110-and-bq34210-q1-battery-gas-gauges-rarely-discharged-applications
training.ti.com/end-service-determination-algorithm

With respect to the learning load for EOS determination, the load would need to be a fixed size with respect to the pack. Accuracy may be critical for the DRD and RSD calculations. With a high precision configurable constant resistance load, parameters with respect to the EOS determination algorithm would still need to be configured with the device in an unsealed state, for that particular pack.

If SOC is a concern (where the CEDV algorithm is utilized instead of the EOS determination algorithm), parameters with respect to the CEDV algorithm would need to be configured with the device in an unsealed state, for that particular pack.

Sincerely,
Bryan Kahler

0 Michael Schulze over 6 years ago in reply to Bryan Kahler

Prodigy 20 points

In the training videos I cannot find how to size the learning load in respect to the pack. It is more an explanation, how EOS algorithm works in general but not a clear description what happens inside the bq34110 during the learning phase and what are the limits for load current and time interval. Are there any other technical resources available, especially for NiMH battery applications?

0 Bryan Kahler over 6 years ago in reply to Michael Schulze

TI__Mastermind 25955 points

Hi Michael,

The load will be determined by the capacity of your battery and the duration of the pulse required to drop 1-2% of the battery capacity.
Size the load to discharge somewhere in the range of C/10 to C/100. One of the best resources for information describing the EOS feature is this video: training.ti.com/end-service-determination-algorithm

Sincerely,
Bryan Kahler

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BQ34110: Learning load parameters