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(This post is for legacy bq20zXX fuel gauges. A future post will cover newer gauges like bq40zXX.)
1) NEW TO GAS GAUGES Quick Start GuidesThe Quick Start Guide and Impedance Track Gas Gauges for Novices are helpful resources for first time users that explain the basic operation of the part. Additionally, two other documents, EVM user's guide which can be found in each device's EVM product folder (e.g. bq20z65EVM-001 Impedance Track Technology Enabled Batt Mgt Solution from bq20z65EVM product folder) and Gas Gauging Basics Using TI's Battery Monitor ICs are recommended to understand the evaluation modules and general purpose of the parts respectively.Common Terms and AcronymsAttached to the post is a file titled Common Terms and Acronyms (in the .zip file) that contains common terms users should be familiar with.What needs to be done before evaluation?The part needs to be calibrated and configured before evaluation. Additionally, you must select a chemistry and run a learning cycle.For newer users we recommend using bqEASY, when available, to perform the necessary pre-evaluation steps; bqEASY software is a plug-in in the device EVSW. 1. CalibrationThe calibration screen in the EVSW provides instructions to correctly calibrate the gas gauge before use. There are a few things to consider when calibrating.
a) To calibrate each setting, users should check the box for the measurement they are trying to calibrate and click the calibrate button. Before calibrating the next measurement, the previously calibrated setting needs to be unchecked.b) Voltage calibration must be done with an external measurement across each cell voltage or pack voltage, as specified. NOTE: this measurement must be done when the cell is in rest. c) Board offset calibration requires no current flowing, therefore it is good practice to do current calibration before the board offset calibration. The most precise way to calibrate current is to go straight through the sense resistor. When the current is being applied directly through the sense resistor, 「off bypass」 should be unchecked when given the option to do so.
Here is the document for Calibration of bq20zxx using EVSW
Here is the document if the customer want to develop software for calibration
2. ConfigurationIn addition to bqEASY, more experienced users can use the Data Flash screen in EVSW to configure the part manually. Please refer to the Data Flash section of the TRM (see section below) or the app notes such as Configuring the bq20z40/bq20z45 Data Flash. Similar app notes can be found for other parts.3. Chemistry SelectionUsers can select the chemistry of their battery through bqEASY or bqCHEM. If the battery's chemistry is not one of the chemistries in our database, bqEASY and bqCHEM automatically match for the best ChemID, reporting the top 3. If a chemistry matches within 3% error, it is an acceptable ChemID. For chemistries that do not match within 3%, you will need to have TI create a custom ChemID.
Alternative method to match for ChemID is documented here using MathCAD tool.4. Learning CycleUsers must run a learning cycle for the gas gauge to learn the characteristics of the battery. Running a chemistry selection cycle performs the same function so only one cycle will be necessary. This can be done by following the steps in bqEASY or by charging the battery to full, relaxing for 2 hours, discharging the battery at >C/10 (e.g. C/5) until termination, and relaxing for 5 hours.Running a learning cycle is necessary for the board to update Qmax and Ra tables.
Here is the application note describing the detail of the learning cycle. Where do I find the Technical Reference Manual (TRM) for my part?1) Go to www.ti.com2) Use the search by part number feature in the top right corner of the page to find your gas gauge.3) Click on the desired version of the part.4) Look for technical reference or TRM either under Datasheet or Technical Documents.
PROGRAMMING DATA FLASH File ExtensionsAttached is a document named File Extensions (in the .zip file) that addresses the uses of various file types. These include:1) The four types of files bqEASY uses to configure a fuel gauge:a) .ENCR filesb) .CHEM filesc) .DFI filesd) .EZY files2) Other important file extensions:a) .SENC filesb) .ROM filesc) .GG files
TROUBLESHOOTING How to find information It is always useful to search keywords and functions in the device TRM. For specific applications, there are some common technical documents for most parts such as the Circuit Design Guide, Layout Guide, and Configuring the Data Flash. For specific questions, try searching the E2E forum: and KnowledgeBase. See the last section about posting to the forum General Hardware TroubleshootingIf you believe you may be having hardware problems, follow the attached document (in the .zip file) to debug your part. The checklist is useful for solving common hardware issues.CommunicationThe EVM can be connected to a computer with the EV2300. Make sure that you have downloaded the EVSW that corresponds to the part you are connecting. The gas gauge must be powered and correctly jumpstarted in order to communicate properly with the EVSW. When the device is plugged in and the EVSW is started, the EVSW should automatically detect the default firmware on the device and open the correct version of software.If this does not happen:
Another possible communication problem is not being able to program firmware to the part. Things to check:
ProductionA good strategy for production is the following seven step flow. Also check out the Battery Pack Production Flow document.
More details can be found in Data Flash Programming and Calibrating the bq20z80 Family of Gas Gauges. This document applies to all bq20zxx product family.
TI also offers a tool called the bqMTester to help streamline this process. The bqMTester user's Guide has detail description of the software and bqMTester board. Common Issues and SolutionsAttached is a PowerPoint that addresses many common questions and issues called Common Issues and Solutions. These include:
Further Actions…If you are unable to find an answer to your question from past forum posts, the TRM, through knowledgebase, or in the FAQ, please post your question in the forum.When you are ready to post, please refer to Information to Provide When Reporting a Problem. Additionally, provide the schematic, layout, and a scope capture of the SMB clock and data lines when applicable.
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