Those 3 blue blinking lights

Why are you trying to stop charging at 50%? I have never checked the blinking lights and level of SOC while the car is being charged, but I don't think blinking lights can be adjusted. If you want to stop[ the SOC level less than 100%, the better way is to just stop at certain time after the start. About 2.5hours after start charging, the SOC should be approximately 50%.

 

Why not look at the time to full charge prior to leaving the car, then head back at the fraction of time that you think you want it to stop at.

Do that a couple of times to judge the actual charge level versus the time to get to that point.

Or do the reverse if you do schedule charging end times.

 

The phone APP shows charge level and estimated EV distance:

 

I believe that the blue lights visible from outside the car are intended to inform other people waiting to use a public charger as to the status of your Prime's charging process. For example, all three blue lights means it's OK to unplug your car and make use of the charging station. This would make more sense if the blue indicators were standard across manufacturers, but apparently they are not.

Along this same line is the feature that you can set your Prime to lock the charging cable in place until the vehicle is fully charges and then allow it to be automatically unlocked so that someone else can use it.

Of course, this probably make more sense in Japan where respectful social behavior is more integral with the culture.

Meanwhile, please see my earlier post about becoming overly obsessive about the process of charging your Prime.

 

This is what the owners manual states for the LED behavior while charging.

 

My 3 blue lights have been accurate on my 2021 Prime. I’ve found the easiest way to charge is to set the timer to charge on off-peak times so I have a full charge in the morning just before I head out the door. You could also set it to just after you would be scheduled to leave if you are avoiding a full charge.

 

I’ll bet that you saw this page when you looked in the 800 page manual. It would be clearer if they changed “charging” to “charge” in the table heading.

 

Just curious: it’s not possible to program the car to charge to a partial level and stop?

 

Unfortunately there isn’t any way to do this that I’m aware of.