BQ20Z95 Max error 145%

Max Error of 145%:

This error happens when there is a discrepancy between `Cycle count` constant in SBS Configuration data-flash and hidden constant (Number of cycles where last Qmax was updated).

When a GG file with data-flash constants is imported and written to a pack that have already been cycled (i.e. a pack with a non-zero value of the hidden constant). This process changes the `Cycle count` but does not change hidden constant, causing an error when calculating Max Error. Did you create your *.senc file by updating GG file to a cycled pack?

To avoid this problem when updating GG file to a cycled pack, you can:

1. Before writting a new GG file into a target pack that have been cycled, alwaysre-write the default firmware first. This will make sure that hidden constant is zero.

2. Update chemistry data to the target pack.

3. Make sure in the GG file, the The SBS parameter "cycle count" = 0

4. Program the GG file to the target pack

Note that even if this error happens, it will clear itself after first Qmax reading is taken (which requires one relaxation/discharge/relaxation cycle). MaxError will than get reset back to 1%. That's why you saw the max error drops from 145% to 1%. Also note that none of these affects actual accuracy of the gas-gauge, but only the reporting of MaxError is wrong.

Max Error of 5%

This means the battery pack has not finished it learning cycles. Only Qmax is learned and resistance is not.

Run another cycle (charge to full - rest for 2hr, discharge to terminate voltage, rest for 5hr)  and Max Error should drop to 1%.

Please refer to application book slua404 (ch11) for information on "Preparing Optimized default Flash Constants"

This problem occurs in a non-cycled pack. The cycle count is 0 in the GG file and senc file. Does the raw IC unprogrammed have a hidden cycle count that is not 0. I have the Update Status = 02 is that wrong value for the senc file? I don't load a gg file I load a senc file. I thought that will clear any hidden constants to zero.

The default senc comes from the IC has the hidden constant = 0. You can do the following to recreate a good senc file:

1. Extract the dataflash image from your current senc file (use bqEASY to read out a dfi file). This will reserve all your DF configuration, calibration data, chemistry, learned R/Qmax (if you done a learning cycle).

2. Download the default senc file from the device product page (under "Tools and Software"). Program it to a device

3. Program the dfi file from step 1 to the device.

Now you should have a good senc file to use.

Is there a command to turn off the Impedance Tracking once it is turned on.?

You can change "Update Status" to 0 or 02, follow by a reset command (0x41 to MAC) .

FYI.

Update Status = 0: this is the default setting from the factory, when the DF parameters are not setup, Qmax/Ra are not undated

Update Status = 2: this is setting in a golden image DFI

I cannot find the senc file for the Z95, on the product's web page. PLease forgive me if I have overlooked something.

I need the senc file for the Z95

Gratefully,

MABanak

OK. I found it.

There are TWO(2) Chemistry Updaters that appear on the product WEB page. The one with the pink font hyper-link "gag Gauge Chemistry Updater" is NOT want I want.

The senc file is accesed by downloading the  "bq20z95 Chemistry Updater" link.

- MB