STM32CubeIDS/STM32CubeMX bug with calculation of power consumption

[Osto]

Hi,

There is a bug since beginnings of IDE/MX with calculation of battery live calculation.

When I use one battery for operation and I define the consumtion information, I get an estimated battery life of x days. When I change the battery count in series from one to two, the battery life should be almost x*2 because I have twice power available but the estimated battery life stays the same. It changes only when I change the count of parallel batteries.

Thats wrong.

Best regards,

Osto

[Vangelis Fortounas]

Hello

>> the battery life should be almost x*2 because I have twice power available but the estimated battery life stays the same.

If use an LDO such LM1117 with two in series batteries the current flowing is the same as if use 3 or 4 batteries , so the discharge time is the same as one battery. (the extra power converted to heat.

If use a buck converter then the discharge time will almost doubled (proportional to efficiency of course)

The Calculator dont know what is the power scheme.

[Osto]

Hi,

Its also wrong when you use LiIon to power a 2.8V system.

Maybe CubeMX should give the opportunity to adjust the power loss percentage!?

Right now its not more than a eye catcher.

Osto

[Khouloud OTHMAN]

Hi @Osto​ ,

Please excuse the somewhat late reply and thank you for having reported. 

I assume that the calculation of the Battery Life Estimation is based on nominal battery capacity and the average current that a load is drawing from it.

In fact, connecting batteries in series does not increase the capacity but adds the voltage of the batteries. Hence the battery life estimation remains unchangeable since the capacity has the same value (and the current consumption doesn't vary).

In the case of parallel connection, capacity and runtime increases while the voltage stays the same.

With this said, and because your feedback is important to enhance our tools in order to satisfy our customers, could you please develop a bit more your suggestion: "Maybe CubeMX should give the opportunity to adjust the power loss percentage"

Thanks for your contribution.

Khouloud.

[Osto]

Dear Khouloud,

In my opinion is your version not correct. When you have one battery with 4.3V and 1000mAh, you have 4.3W power in your system and when you use 3.3V then you have a similar battery of 3.3V/1300mAh to empty the battery. When you have 2 of them in series then the total power is 8.6W and you have a battery of 3.3V/2600mAh. The life time is double if the DC/DC or LDO efficiency is 100%.

The efficiency is the only factor need to be added to the calculation. In my Opinion there is a need to have a global efficiency and also a power conversion efficiency for each step because specially with battery powered systems the are very often 2 different power supply which differ in efficiency and also different efficiency because of efficiency curve of an DC/DC converter which is mostly different through the current curve.

I don't want to update my calendar with the values when to change the battery. I need an realistic estimation what to write in my datasheet. Few percent up/down makes no sense. So even only a global efficiency adjustment is acceptable.

Best regards,

Osto

[Khouloud OTHMAN]

Hello @Osto​ ,

Thanks for your feedback and for the detailed description. I see your point and will bring it up to our development team and see how we can address this modification.

I'll keep you posted with updates.

Thank you for your contribution.

khouloud.

[Osto]

Thanks a lot.