Not properly an issue: understanding when battery must be replaced

[Davefries1966]

Hi all,

I'm using a Sparkfun AssetTracker development kit with MicroMod ESP32 add-on. The deployed device works in a unmanned environment and communicates via MQTT, as per closed issue #34 (thanks Paul!). All is working fine now, I just would implement some diagnostics on the device, to be reported through special MQTT topics (e.g., overtemperature, exhausted battery and so on...).

I ran the example AssetTracker_Example4_MAX17048 which helps extracting a lot of information about battery status. I don't understand how to interpret the above information to exactly establish when the battery is DEAD and MUST be replaced (usually a good indicator would be when charger is ON and the charging current is NEGATIVE).

There are several alerts that can be triggered on the example, I'm trying to figure out which could be applicable to my use case but those are not completely clear to me.

Thanks for everyone could give me any hints.

David

[PaulZC]

Hi David,

Please clarify. When you say DEAD, do you mean: discharged and requires charging; or that the battery is no longer holding charge?

You should be able to infer either by monitoring the battery voltage, State Of Charge, and Change Rate?

Best wishes,
Paul

[Davefries1966]

Hi Paul

happy to meet you again here, and thanks for your prompt support ! :-)

I mean DEAD when the battery is no longer holding charge, that is, it is completely exhausted.

I was able to run the example and read all the above information, but it is unclear to me how to match them one to each other.

Cheers
David

[PaulZC]

Hi David,

There is some useful information in this application note: https://www.analog.com/en/technical-articles/battery-gauge--maxim-integrated.html

I wonder if the following would work? Similar to the stepped-discharge test:
Ensure your system is running from the battery
Use the D0 or D1 breakout pad to control a small external circuit: a transistor or FET low-side switch which connects a 33 Ohm load to 3V3 (adding 100mA to the current draw)
With the external load enabled, check the increased discharge rate matches a known good battery. If the discharge rate is higher, the battery may require replacement?

Or, sample and average the battery voltage with the load turned off. Then repeat with the load turned on. The voltage drop from a failing battery will be higher than a new battery?

I hope this helps,
Paul

[Davefries1966]

Hi Paul

I will take a look there!

Cheers
David

[PaulZC]

Hi David,

Closing... Please re-open if you need more help with this.

Best wishes,
Paul

[Davefries1966]

Hi all,

re-opened this because I would need more help. :-)

I keep running Sparkfun example "AssetTracker_Example4_MAX17048.ino", and getting the following info when the battery is completely charged:

I cannot understand why the 2 voltage alert flags, i.e. high and low voltage, are both set to "1". I mean, at the beginning when the battery was almost completely discharged (2-3% of SOC, and voltage below 3.9 V), just the alert "voltage low" was "1".
After a certain time the voltage exceeds the 3.9V threshold and "voltage high" turns to "1", but "voltage low" didn't turn to "0".

Maybe I am confused about these alerts, or maybe the alerts should be reset in some way after each reading ?

Actually I would need to understand also the following:

1. "Hibernating" means that the fuel gauge is not currently charging the battery ?
2. More in general, when the battery is fully charged, is the AssetTracker powered by the connected 5V USB-C port (battery bypass) or, the AssetTracker is always powered by the battery which is continuously discharging/charging ?
3. how the "SOC 1% Change Rate Alert" can be interpreted ?

Thanks anyone!

Cheers
David

[PaulZC]

Hi David,

Please have a look at the examples in the MAX17048 library repo: https://github.com/sparkfun/SparkFun_MAX1704x_Fuel_Gauge_Arduino_Library

Also the MAX17043 Hook-Up Guide: https://learn.sparkfun.com/tutorials/lipo-fuel-gauge-max1704x-hookup-guide#example-4-max17048-kitchensink

Also the MAX17048 datasheet: https://cdn.sparkfun.com/assets/5/2/7/6/6/MAX17048-MAX17049.pdf

Hopefully they can clarify things for you?

Best wishes,
Paul

[Davefries1966]

ok thanks Paul ! :-)