MathCAD compensated end of discharge voltage (CEDV) tool
MATHCAD_CEDV_SOFTWARE
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MATHCAD_CEDV_SOFTWARE:
MathCAD Compensated End of Discharge Voltage (CEDV) Tool



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Description

Math calculation and simulation tool that helps the battery designer to obtain matching CEDV coefficients for the specific chemistry in the battery pack using one of TI’s CEDV algorithm based fuel gauge. It accepts 3 pairs of log files that can be created by using TI’s bq Smart Battery Builder software with a CEDV Evaluation board connected through USB. For accurate calculations it will also require some additional parameters of the battery pack setup. The downloadable output file contains the CEDV coefficients that can be programmed into Data Flash to create a golden image that can be used in mass production of battery packs.

 

An EV2300 or EV2400 PC interface board is required to interface to the gas gauge, and a PC USB cable is required for communication with a PC. Both can be ordered online at http://power.ti.com. Windows™-based PC software is available online as well. With the EV2300 or EV2400 interface board and software, the user can read the data registers, program the chipset for different configurations, log cycle data for further evaluation, and evaluate the overall functionality of the solution under different charge and discharge conditions

Features

Accepts 6 log files and configuration data and calculates best CEDV coefficients

    Generation of log files

    Procedure Summary

  • Continuous discharge at 2 different rates, from fully charged state until termination voltage is reached.
  • Time, voltage, current and temperature (directly on the cells) must be recorded and stored as separate columns. Any text should be removed from files prior to calculations. Voltage is in mV, current in mQ and temperature in degree Celcius.
  • Easy recording method is to use our EV software/bq Smart battery builder that reads data directly from our fuel-gauge.
  • Make sure to set over-temperature limits in the fuel-gauge higher than expected cell temperature during the test.
  • First rate should be average typical, and second should be average high for your application. Note that high rate should NOT be maximal peak current, but maximal average sustained rate that can practically occur in the application.
  • Discharge does not have to be constant current. It can be any load pattern typical for your application, including constant power.
  • Battery should be fully charged prior to application of test pattern.
  • Test at both rates has to be performed at 3 different temperatures. Typical temperatures for the test are 5, 30, 50 C. Note that cells heat-up during high rate discharge, so if your max spec temperature is 70, you can use chamber temperature 50.
  • As result of all tests you will obtain 6 files.
  • As result of all tests you will obtain 6 files.

Output data from tool:

  • File that contains the best matching CEDV data flash coefficients for the input cell data. These values can be programmed to data flash for mass production
  • EMF, EDVC0, EDVC1, EDVR1, EDVR0, EDVT0, EDVTC, VOC75, VOC50, VOC25

    Configuration Data

    The following data is input to the tool in addition to the log files:

  • Numbers of serial cells: Number of cells in battery stack
  • Logging interval adjustment: If logging is at very small intervals then recommend to use every Nth sample to speed up calculations.
  • Cell termination voltage: The threshold voltage below which system may not operate as expected
  • EDVTC constant : The temperature compensation constant used to find the best match. Default is 9.
  • Fit EMF data: Yes/No value. Select this box if using the script to get around invalid values generated on previous runs
  • Type of chemistry: Pick the type of chemistry that the cells use. One of LiCoO2(default), Lithium on Nickel-Manganese-Cobalt(NMC), Lithium-ion with nickel-cobalt-aluminum(NCA), LiFePO4
  • Numbers of parallel cells?
  • Any Other?

Software (1)


TI Devices (1)

Part Number Name Product Family
BQ28550  Single cell Li-ion battery gas gauge and protection  Battery management 

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