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STC3100 at startup

ACHOB.1
Associate II

Hi,

I just started to use the STC3100. I can read all registers but I don’t understand how I can calculate the State of Charge at startup. I followed the application note AN3064 and apparently I need a voltage measurement to estimate the State of Charge (as a reference).

I don’t understand how I can do it because i don't have the discharge curve of my battery (which is : 18650CA-2P-3J ). I guess that there are somethings that I missed.

I really appreciate any kind of response to grow my knowledge on the battery monitoring subject.

5 REPLIES 5
GZila.1
Associate

Hi

I'm trying to solve same problem. Did you find any solution for calculate state of charge at startup? Or anyone could help us to calculate instant state of charge? I readed all documents that related with STC3100 and I didnt see any useful information to calculate state of charge.

Thanks for all help

ACHOB.1
Associate II

Hi, all I know is it won't be accurate anyway. I have read that even in our telephones there is a certain difference between the displayed percentage and the real one.

Unfortunately I don't have more information. I posted messages on different sites but no response. Maybe the battery monitoring is reserved for an elite.

Peter BENSCH
ST Employee

Without detailed information on all relevant battery parameters, it is a very difficult task to calculate the state of charge at startup. Please note that a LiIon-based cell looks like a simple battery. However, its parameters (and there are many) depend on how it was made, how old it is, what temperature cycles it has seen and so on.

Please have a look at AN3064, section 3:

  • At start-up, [the system controller] enables the STC3100’s battery monitoring functions.
  • It periodically reads the battery voltage, temperature, current and charge accumulator and uses this information to estimate the state of charge.

A microcontroller connected to the STC3100 can read this information and always keep the last state in a non-volatile memory. So over time it knows what energy has been used for charging and discharging, maybe also considering the self discharge, the time between charging/discharging and other parameters influencing the current charge.

Good luck anyway!

/Peter

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ACHOB.1
Associate II

Thank you for your reply.

The voltage measurement at start-up is interesting because the temperature has not yet had time to increase, am I correct?

The discharge curve of each Li-Ion battery is different so without it I can't make the first estimate, right? Or can I determine it with "classic" parameters that I can find in the datasheet of my battery?

Peter BENSCH
ST Employee

Well, the voltage measurement at startup will give you some idea about the status of the cell, but it is almost impossible to estimate the charge without knowing all relevant paramters. I haven't seen anybody being really successful in determining the charging status of an unknown cell without these parameters.

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.