STC3100 at startup

[ACHOB.1]

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.

[GZila.1]

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]

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]

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

[ACHOB.1]

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]

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