bqEASY Impedance Track Algorithm

Dylan,

What discharge fault bits got set? I recommend carrying out the steps manually instead of using the automated steps of bqeasy:

1. Send an IT Enable (21) command to turn ON FETs. Send a Reset command (41) to disable Ra-table updates.

2. Discharge to empty at C/5. eg, if you have a 2200mAH cell, your discharge rate will be 0.44A

3. Wait 5 hours

4. Send IT Enable (21) command to set a DOD0 reference point.

5. Charge to full

6. Wait 2 hours Qmax will be learned at this step. You should see VOK turn green after Qmax has learned. You should see Update Status change to a 05.

7. Discharge at typical low rate of target application (usually C/5 ) down to Term Voltage. Using low rate will allow to update resistance points at deep states of discharge. Rate of discharge must be higher than C/10 rate, otherwise resistance will not update.

8. Wait 5 hours for relaxation. You should see Update Status change to a 06 during the rest period.

9. Repeat steps 5-8 while running EV Software log to verify accuracy.

i hope this helps

thanks

Onyx

After sending the commands 21 and 41, The FD, RCA, R_DIS all become set, and the FETS do not turn on.

As long as no permanent failure (pf) bit was set, issuing command 41 should clear the safety statuses preventing charging. You can then issue command 21 to turn on the fets to start charging after having discharged to empty. Pls follow the intructions I stated above.

-Onyx

I can send commands 21 followed by 41 and the FETS turn on and everything is set, but then as soon as I connect a load across Pack+ and Pack- the FETS turn off and XDSG and XDSGI become set. I've tried sending the commands after connecting the load, but the FETs will not turn back on.

Dylan,

You shouldn't be applying a load as this will cause further discharge below your cell undervoltage threshold (CUV) and cause the XDSG bit to get set if the CUV threshold condition doesn't clear within the default 2 second timer window. You will need to program your data flash appropriately before carrying out the learning process. The technical reference manual of the device you are using explains what all the data flash parameters mean. You need to understand them to be able to program your device appropriately as needed by your application.

Onyx

Right, I've read it. Doesn't the bqEASY program update the data flash with the parameters you enter it? How do I discharge the batteries without a load? Is there a document that is some sort of procedure on what to do to successfully get a golden image? The documentation on how to do anything with this gas gauge is terrible, the only thing that had a y useful information was the technical reference guide, but that doesn't have any instructions on implementation. 

Its been explained quite clear what to do to get qmax updates, on the 2nd post.

you need to set up your fuel gauge accordingly, know what the parameters mean and so on.

you can discharge a pack with an electronic load attached to +/-

the learning cycle i admit takes some getting used to but it does work and qmax values do automatically update.

its important to do this uninterrupted and also the chemistry id is important also.

basically.

1) enter all the fuel gauge parameters into the flash

2) enter chemistry id 

3) enter qmax from cell data sheet, design energy etc

4) do the steps explained in the 2nd post.

5) qmax will update and then you can begin the process of getting a golden image with a unit.

i just get one good unit that has all the above steps done, and use that for a golden unit, go to bq easy and do a export dfi.

that can be programmed into other units and all they need to have done is a calibration (and set cycle count to 0), restore the update status also.

Thanks for your responses,

Eric, if you could clear up the discrepancy between no load and an electronic load.

By electronic load, do you mean a simple negative current source, or a resistive load that draws current when I2C activates an NMOS? (see diagram below)

We've tried the diagram in SLUU2780 (Figure 4) for the learning cycles (discharge). This method still throws the Smart Battery back into PRECHARGE Mode as indicated by the bit flags (based on the timeout Onyx mentioned). We've calculated the C/5 rate (800mA Capacity) / 5 = 160mA. We've tried just a resistive load.

This is what the documentation specifies, but we appear to be missing something.

Please get back,

 Dylan