BQ35100: EOS mode query

Art Mecina

Genius 16655 points

Part Number: BQ35100

Hello Guys,

Good day.

Our customer have the following inquiries on BQ35100.

1) Does EOS mode work for some use cases if the battery doesn't rest (e.g. system sleep) for >5 hours?

2) What if the system wakes once an hour. Datasheet section 8.2.2.6 says: If the system powers down for less than 5 hours, EOS operation might be compromised. Following to 7.3.4.5, does this mean if an EVM or test system does not trigger the bad OCV alert that shorter sleep cycles are ok?

Thanks in advance.

Art

over 4 years ago

0 Art Mecina over 4 years ago

TI__Genius 16655 points

Hello Guys,

Any update regarding this?

Thanks in advance.

Art

0 Vos over 4 years ago in reply to Art Mecina

TI__Genius 10370 points

Art,

In EOS mode the gauge relies on being woken during a state of OCV. If you wake the gauge with too small a rest you will compromise the impedance calculation. There is no exact formula to know if you system will work or not just by knowing the rest time. the behavior is determined by Discharge Load Amplitude, temperature, discharge duration, Cells internal impedance, and more...

I suggest using and EVM to replicate your expected load profile to see if you get accurate and stable measuredZ values as a start.

Thanks,

Eric Vos

0 Art Mecina over 4 years ago in reply to Vos

TI__Genius 16655 points

Thanks Eric.

Kindly help to clarify what the first sentence on the image below means about "10s of mS" ?

Thanks and regards,

Art

0 Vos over 4 years ago in reply to Art Mecina

TI__Genius 10370 points

Art,

i can agree the wording is odd. it is missing a few '. If i were to re-write it

The bq35100 is designed to gauge pulse with an amplitude of tens of mA (~50mA+) that last for tens of mSec (~100mS+).

The intent is the pulse should be measured in mA and the length should be measured in mSec.

Thanks,

Eric Vos

0 Art Mecina over 4 years ago in reply to Vos

TI__Genius 16655 points

Thanks a lot Eric.

In case of further inquiries, I will direct customer to this thread.

Thanks and regards,

Art

0 Brad S over 4 years ago in reply to Vos

Intellectual 300 points

Vos said:
If i were to re-write it

can someone re-write it?
its been a problem for customers well over a year

e.g. BQ35100: FAQs, profile, EOS, calibration - Power management forum - Power management - TI E2E support forums 1b
and BQ35100: EOS measurement health steps down in 2% steps to 0% and Li-SOCl2 still not empty - Power management forum - Power management - TI E2E support forums

I'm also now hitting issues which i think are also related to
BQ35100: Locating the cause of SOH_MERIT - Power management forum - Power management - TI E2E support forums

but this relationship is unclear from the docs

0 Vos over 4 years ago in reply to Brad S

TI__Genius 10370 points

Brad,

The wording while not ideal is correct. I have put in a request to have it updated, but it will be low priority for the near future. I will get more detail on the SOH_MERIT flag trigger conditions and update another E2E thread.

In the September timeframe (not in stone) we plan to update the Q&A for this device with a lot of the common questions.

Thanks,

Eric Vos

0 Brad S over 4 years ago in reply to Vos

Intellectual 300 points

I understand what you mean and certainly "tens of" rather than "10 s of" would have been easier to understand. But I can also see numerous forum posts of people like me that didnt understand it until it was explained, yet nothing was fixed

with all due respect (especially as you have the most answers on this chip of everyone), I think an update and not just a forum post is long overdue and I'd like to help

LiSoCl2 users with varying power and sleep cycles want to know in advance if EOS will correctly work for their use case. And its just sooo hard to get through right now. Many of the posts here are trying to use early SOH or impedance values to confirm things are working. If you browse most threads, its not clear that the customer ever got things working as a result of the support and in fact looks unlikely.

Having read all of the technical documents, muliple irregularities or things that weren't clear brought me here. There was a large number of posts on this gauge, but most of the author questions are hard if not impossible to find answers to. its certainly not easy for a customer - they either waste extra time trying to figure this out, or they walk away.

example :. Today the docs say SOH_MERIT. 4 years ago - SOH_MERIT should be EOS_MERIT according to https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/620859/bq35100-confirm-the-behavior-of-eos-mode/2292847#2292847

For LiSoCl2 users, neither the docs nor this forum make things clear like:
* when can a typical mcu power draw with radio be used to calculate impedance or when must the designer revert to an occasional wasted energy pulse (e.g 50mA for 100ms).
* initialisation and then readings can be affected by: battery passivation, battery relaxed / not, current or voltage drop seen by the battery due to the system while first readings are taken and after etc etc how do I avoid all the things that lead to errors.
* combine the previous 2 points - what are the conditions that must be met around and between ge high and then ge low
* SOH is really rough / unusable for most flat LiSoCl2 curves. But why do so many users see nonsensical results? How does a user get a clue that their system is set up right and EOS will trigger correctly when EOS is only expected in a few years?

0 Brad S over 4 years ago in reply to Brad S

Intellectual 300 points

and another:
(+) BQ35100: EOS accurate detection validation - Power management forum - Power management - TI E2E support forums