Is this my imagination? Charging/battery life

[BlackZeppelin]

I'm just wondering am I imagining things or not? I have one 15W fast charger and a whole bunch of slow chargers, some from my Galaxy S5.

And although I love the snappy charging speed from the fast charger, it seems to me that the battery lasts less than charging with the slow charger.

What I mean is that if I charge to say 80% using a fast charger and then again to 80% using a slow charger, the battery lasts longer after charging to the same amount from the slow charger. And actually, considerably longer.

Do any of you notice this or am I just on crack?

 

[Mooncatt]

This article gives a clue.

https://batteryuniversity.com/index.php/learn/article/charging_lithium_ion_batteries

Increasing the charge current does not hasten the full-charge state by much. Although the battery reaches the voltage peak quicker, the saturation charge will take longer accordingly. With higher current, Stage 1 is shorter but the saturation during Stage 2 will take longer. A high current charge will, however, quickly fill the battery to about 70 percent.

Part of the state of charge calculation uses voltage. When the current is increased and voltage is raised quickly, my guess is that throws off the calculation, making the phone think the battery has more of a charge than it actually does.

If you were to let the battery fill completely (though not recommended as a general practice), the voltages come back in line between the two chargers and you should get the same run time either way.