My ASUS Transformer Book (2 in 1 Laptop/Tablet) will only charge when powered completely off. When it is plugged in, it charges DOWN very very slowly. I've been through 3 different charges and the same thing keeps happening. I've tried contacting ASUS to no avail, and I tried contacting Windows but they told me to talk to ASUS. It may be a hardware problem in which it needs to be evaluated and repaired, but I'm trying to avoid that at all costs considering it costs money. I'm hoping this is an internal problem that I can fix. But I need help.
Asus T100TA or something like this one? Your charger is fine, it is just totally wrong design of this 2in1. This 2in1 takes about 10-15 watt while running (10 watt for version without hdd, 15 with), so with 10/15 watt charger, it makes sense it wont charge. If you want to charge it and keep using it, try 9v/5v 2a charger, T100TA is officially supporting it, while it is not in description of 2in1, it is in description of 18w adapter https/www.asus.com/Notebooks-Accessory/18W_Adapter_and_Cable/specifications/
If it is not charging when turned on, but will charge when turned off, then you are going to need a new charger.
If it were the battery, it wouldn't charge no matter if it was off or on. However when a charger is going, it will often put out less power than is actually needed to both run the device and charge the battery at the same time. Leading to it only charging when turned off.