Li-Ion battery State of Charge estimation

RE: Li-Ion battery State of Charge estimation

AimHigh — Tue, 11 Feb 2020 10:49:07 GMT

Dmitry thank you for all the information and suggestions. Our application where the accurate state of charge is not required, Sure we will go ahead with the approximation for the SOC estimation.

RE: Li-Ion battery State of Charge estimation

Dmitry — Tue, 11 Feb 2020 10:07:14 GMT

It's rather a complex task if you need an accurate results - you should take into account discharge rate, cell temperature, self-discharge, battery aging, etc. That's why I suggest to use a gas gauge chip. If you need only a rough estimation, you can monitor battery voltage and convert it to a state of charge with discharge curve found in specification for your battery.

Also take a look at this article that explains how it's implemented in Maxim chip.

RE: Li-Ion battery State of Charge estimation

AimHigh — Tue, 11 Feb 2020 05:11:47 GMT

Hi Dmitry,

Thank you for your response and suggestion.

We have designed the bidirectional using TI's op-amp to sense the current.

I have got one more question here, So what I understood is we have to gather the data of Voltage vs State of Charge for our application and then use that data to predict the state of charge for the battery or please correct me If I got it wrong.

Again for the above method, We did not consider temperature variation, So any insights on how SoC estimation would differ with temperature and other parameters?

Thank you

RE: Li-Ion battery State of Charge estimation

Dmitry — Mon, 10 Feb 2020 17:24:25 GMT

Hi,

1. Yes, it's a usual way to measure the voltage.

2. As long as you take a differential signal directly from your current sense and don't forget to calibrate ADC offset periodically. Keep in mind that you have to measure a positive (charging) and negative (discharging) voltage drop, so you need an opamp in any case. IMHO a gas gauge chip like BQ34110 would be a simpler and more reliable solution.