Some android devices support changing the charge rate via files in /sys, slow charging prolongs battery life (and the user probably won't be inconvenienced at all for overnight charging).

Would be good to offer option to limit charge current where supported (perhaps offering option to reduce current when very empty or near target fill).

Charge rate could be automatically limited based on Android "quiet hours" setting and also device temperature (or battery temperature if available).

Charging fast towards when near full and completely empty impacts battery life (more so with some cell chemistries than others I believe).

The same goes for charging batteries which are at high temperatures or very low temperatures. Some built-in chargers will be sufficiently intelligent to compensate for these factors on their own, but most aren't.

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

https://www.digikey.com/en/articles/techzone/2016/sep/a-designer-guide-fast-lithium-ion-battery-charging

^^^ also see "Fast charging trade-off" section in the digikey article...

http://teslapedia.org/model-s/tesla-driver/understanding-charging-rates/

^^^ section on charging speed vs. temperature

Cheers,

Tim.