[Q] [ION and possibly others] Phone loosing charge while charging via car charger
I use my Xperia Ion (running rooted stock JB) as a navigation and dashcam unit. So naturally I want it plugged in while I have it in my car. However I have noticed a slight "bug". The way I understand how the charging works is that the phone will charge at full power (1-1.2A) until a certain point (% of battery) and then go into trickle charge mode (300 to 600mA). When using my phone the following function are in use:
This will all need power. And while the phone does seem to charge in the car if the battery is low (>50%), it will stop at 70ish %. Depending on the charger I use it will stay at 70% or start draining again. With some chargers the phone only drains power and will never charge unless I keep power use to a minimum. I.e. not use it.
I have tried many power sources. These include:
Motorola dual port charger (for Motorola Atrix car dock)
Quality brand universal USB charger
Sony Xperia charger
Laboratory power supply with different configurations on the USB data pins
(shorting D+ and D-, voltage divider 2.1V on both pins, 2.5V on one and 2.1V on the other pin) the last config offered fast charge (1A)
The Phone does not seem to be smart enough to know that it needs more power and should therefore not enter slow charging mode if the power drain is higher that the power input. I have measured the current while the phone is charging and have determined that the phone indeed does charge with high current in the beginning but then lowers the current as the battery voltage increases.
My Question is then as follows:
Do other people suffer the same problem with their phone when trying to use it a lot while charging with a car charger like me? Does the phone also discharge while "charging" with a car charger? Does the phone only charge to the certain point and then stay there or even discharge again?
And the most important question:
Is there a way to make the phone stay in full fast charge mode?