BQ34Z100-G1: Self-Discharge Rate configurable?

Hello Mathias,

Where is the error appearing in the self-discharge estimation? Is the SOC incorrect? The gauge uses a voltage based correlation while there is little or no load, so any error during this period would be from a bad chemistry ID match.

Can you share any diagrams of how the circuit is setup with the gauge?

Sincerely,

Wyatt Keller

We had an strange effect after the battery was charged and possibly was self-discharged beforehand.

So:

1) Pack was stored without maintenance for approx. 4 month

    1.1) EDIT: In any case, it was a mistake and shouldn't have happened. But now we have to deal with it.

2) Pack was charged

3) Pack was discharged in application (170W)

As you can see the SOC stays at 100% for nearly a hour - this is half the total run time.

At the end we had en error of approx 30%-35%.

Same for the remaining capacity (in Ah). 

In my opinion, the error at the end is exactly the part that is not deducted at the beginning.

After a full cycle, the pack worked as expected again. It passed with a few minutes error at the end.

My fear is that the 1mA maximum supply current of the TPS2493 will increase the self-discharge to such an extent that it can no longer be correctly

calculated:

For this reason the question, is there a way to configure the current consumption of the circuit in the BQ34Z100-G1?

Chemestry ID:

We are using the Panasonic LC-P1220 cells in combination with the ChemID 0803. In our tests this ChemID fit the best. But in our experience, a bad ChemID is more likely to cause Time to Empty or SOC errors at the end of a discharge cycle of a few min / %, rather than such a large deviation.

Regards

Mathias

Hello Mathias,

The gauge will probably not sense 1mA due to the deadband current, so it will rely on the chem ID match to correlate the voltage. I checked the battery chem ID and the OCV is not that flat, so as long as there is very little load on the battery and the OCV of your battery and the chem ID match closely there should be very little error over time.

What was the DOD max error when you submitted your logs to the GPCCHEM tool?

Sincerely,

Wyatt Keller

Hi Wyatt,

I didn't manage to get the ChemID analysis from back then. We are in the process of repeating this test. I think I can make a statement here in a few days.

Hello Mathias,

Let us know when you have collected some data from your tests we can review.

Sincerely,

Wyatt Keller