low FPS when battery is low ( unity android )

Question

i make a simple 2d scene in unity 2017.3.1f1 (only 5 sprite renderer). I realized that when my Android device's battery is under 20 %, the frame rate will be 60 to 30. I did all the optimizations I heard, like:

DynamicBatching, Sprite Atlas , Quality Setting , sprite Texture Comprestion Override for Android And I emphasize that my scene contains only 5 sprite (one background and several buttons)

i use Application.targetFrameRate = 60; because if don't , all time The motions are stuttering Whether the battery is over 20% or not.

And when the vsync is off, the frame is locked to 30 and when it's turned on, it changes for about half a second between 30 and 60

according to profiler (on my android device) Gfx.WaitForPresent start growing!!! (if you want to say it is GPU bound , i think render time don't grow And scence is very simple)

In all these modes, The motions are stuttering.

I tested two kinds of moves

1: Moving camera in the update method by the following code:

void Update () {
    if(startMvCm){
        if (cam.position.y > EndCm ) {
            cam.Translate(0f,(speedCm*Time.fixedDeltaTime),0);
        } else {
            cam.position = new Vector2(0,EndCm);
            startMvCm = false;
        }
    }
}

2: An animation of moving an image in canvas (simple UI menu with 5 button) using Animator.

And this low FPS see more in low Battery on my Huawei Mate 10 Lite

Answer 1

It's likely this is an issue largely outside of your control.

If it is true that the only variable in your tests is your phone's battery percentage, then this is almost certainly the result of your phone trying to throttle itself to conserve battery or (indirectly) to say within a certain thermal profile (depending on how you are getting the phone to 20% battery).

The Android PowerManager API has methods to tell if your application is on the whitelist for ignoring battery optimizations, and suggests how you can prompt the user to put your application on that whitelist. It's not something you can do unilaterally, however. You will have to ask the user for permission because the user is in control of the device. Google also has requirements about what is and isn't considered an appropriate request. And unfortunately I don't see that this is directly exposed through to the Unity API, you may have to write some sort of plugin or whatnot, as this user did for iOS.

Furthermore, nothing you can do is really going to stop the OS or hardware from throttling your CPU or GPU down if it thinks it needs do, e.g., due to thermal conditions.