Does nPM1300 Fuel Gauge consider Battery Degradation?

RE: Does nPM1300 Fuel Gauge consider Battery Degradation?

Ben_S — Wed, 24 Apr 2024 14:09:42 GMT

FYI (and for information for anyone else working with the device), it appears that the update rate is indeed important, at least while providing SoC estimates during discharging.
In testing in my application with a constant (500mA) current draw, I've seen significant differences with an update rate of 1 second vs. 30 seconds. With the faster update rate, the estimate is more accurate, as expected. At a 30s update rate, the estimate was not accurate enough for our application (e.g., SoC estimate was 60% vs. 30%, when 30% was closer to accurate). I'd love to know if there were best practices for update rates vs. states.
Also, FWIW, in informal testing, the algorithm does not appear quite as sensitive when running charging calculations 🤷

RE: Does nPM1300 Fuel Gauge consider Battery Degradation?

Michal — Tue, 26 Mar 2024 13:49:47 GMT

Hello Ted,

I got some answers from our expert:

[quote user="Tyekuhn"]Does the FGA take into account the number of charge/discharge cycles in its estimates of State of Health (SoH) of the battery? Along the same lines, does the FGA adjust the estimated battery capacity based on the number of charge/discharge cycles, and/or the age of the battery?[/quote]

We are still running battery aging testing, so no news on this topic.

We have made a clarification in the fuel gauge user guide on this topic: "The calculated state of charge is relative to the battery's present maximum capacity and always shows 100% when the battery is fully charged, even if the actual capacity has reduced due to aging." link: nPM1300 fuel gauge overview (nordicsemi.com)

[quote user="Tyekuhn"]Does the FGA "expect" to start with a fresh battery? What if the FGA was started when the system was mated to a battery that had already gone through half of its useful life (for example, say 200 charge cycles), would it be able to recognize this automatically by estimating battery-impedance, or would the user need to somehow inform the algorithm that the battery has already been cycled many times?[/quote]

FGA does not need to start with a fresh battery, it will use battery voltage, current and temperature to calculate the state of charge once initiated. From the user guide: "The nPM1300 fuel gauge algorithm incorporates internal adjustments to correct any initialization errors resulting from an unrested battery and unexpected reset conditions. These errors typically have a minor impact, and the predictions will converge to the accurate value within a few minutes of normal operation." link: Guidelines for battery profiling (nordicsemi.com)

[quote user="Tyekuhn"]Does the FGA take into account the age of the battery...that is, how long the FGA has been running with the attached battery?[/quote]

This one wasn't directly answered, but I think the previous answers should be enough.

[quote user="Tyekuhn"]Is there any way to get the estimated battery capacity, in absolute units (e.g. mAh) out of the FGA? I only percentage SoC in the return of nrf_fuel_gauge_process(). Is that percentage the percentage of a fresh battery, with a 100% SoH, or the percentage of what the battery is currently capable of, possibly less than 100% SoH?[/quote]

FGA does not have an option to output estimated battery capacity in mAh. As mentioned above the calculated state of charge is relative to the battery's present maximum capacity.

Best regards,

Michal

RE: Does nPM1300 Fuel Gauge consider Battery Degradation?

Michal — Mon, 25 Mar 2024 07:59:56 GMT

Hello Ted,

I have asked the experts for their insight about it.

Just so you know, we are currently in the Easter period and any answers may be severely delayed.

Best regards,

Michal

RE: Does nPM1300 Fuel Gauge consider Battery Degradation?

Tyekuhn — Wed, 20 Mar 2024 18:22:43 GMT

Hello,

I have questions concerning the same subjects discussed here, and I'm wondering if there have been any updates to the Fuel-Gauge Algorithm (FGA).

Does the FGA take into account the number of charge/discharge cycles in its estimates of State of Health (SoH) of the battery? Along the same lines, does the FGA adjust the estimated battery capacity based on the number of charge/discharge cycles, and/or the age of the battery?

Does the FGA "expect" to start with a fresh battery? What if the FGA was started when the system was mated to a battery that had already gone through half of its useful life (for example, say 200 charge cycles), would it be able to recognize this automatically by estimating battery-impedance, or would the user need to somehow inform the algorithm that the battery has already been cycled many times?

Does the FGA take into account the age of the battery...that is, how long the FGA has been running with the attached battery?

Is there any way to get the estimated battery capacity, in absolute units (e.g. mAh) out of the FGA? I only percentage SoC in the return of nrf_fuel_gauge_process(). Is that percentage the percentage of a fresh battery, with a 100% SoH, or the percentage of what the battery is currently capable of, possibly less than 100% SoH?

Thank you!

Ted

RE: Does nPM1300 Fuel Gauge consider Battery Degradation?

Michal — Wed, 22 Nov 2023 14:57:42 GMT

This is the information I got from our expert:

Battery degradation will affect the battery resistance and battery capacity parameters in the battery model. But because of the internal compensations of our fuel gauge algorithm the effect may not be significant specially during discharging. We are still assessing how well the internal compensation effect is when dealing with battery degradation. This is a process that takes time, so for now this is the best we can say.

Battery datasheets states expected cycle life, which typically is >=80% after 500 charging/discharging cycles (at 25C and 0.5C discharge rate). We are looking into ways to track this and for the user to update a battery capacity factor based on number of charging/discharging cycles. This is something the user can implement themselves today, given they have the battery degradation details for their battery.

This is common knowledge for most people working with batteries, but it's always important to check battery manufacturer specified standard charging currents and voltage limits to configure the charger. Typically higher charging currents will make the degradation faster.

Best regards,

Michal

RE: Does nPM1300 Fuel Gauge consider Battery Degradation?

Michal — Mon, 20 Nov 2023 14:32:11 GMT

I have asked the experts and I will get back to you when I'll have more information.

Best regards,

Michal