ASUS Transformer TF-101 design flaw
The original Transformer laptop-style Android table from ASUS was the TF-101, and its clip-on keyboard is being copied today by other vendors. It's a design that makes a lot of sense.
But the TF-101 had a severe design flaw: its battery system could drain the tablet to the point of being unrecoverable. A battery drain itself? Yes. Over the years that I've owned the TF-101, I finally figured out why the problem exists, and how it is cured.
The problem is so severe that when I first bought the tablet from the local Staples outlet, the manager ended up sending his entire stock back to ASUS, because it seemed like they all were dead. The one I ended up with had a peep of life in it.
(I don't know if the flaw exists in today's Transformer-style tablets, but I suspect it does. I'll explain why later.)
This tablet has two batteries: one in the tablet and one in the keyboard. The battery in the keyboard is a second, full-size battery, giving this tablet a remarkable running life. In fact, I use it to recharge my phone on my travels.
The dual-battery system works like this:
1. The wall charger charges the battery in the keyboard.
2. The keyboard battery then charges the battery in the tablet.
Problem: The design flaw is that the battery housed in the keyboard keeps charging the battery in the tablet, even when the tablet is turned off. As the tablet's battery slowly drains, the keyboard's battery recharges it until it too is drained. Brilliant: two drained batteries.
When we plug in the wall charger, it first charges the keyboard battery. Once the keyboard battery has sufficient charge, it begins charging the drained tablet battery. The problem is when we want to turn on the tablet: when its battery is too drained, it cannot start.
Solution: The solution is to detach the keyboard, and plug the charger directly into the TF-101 tablet. (The TF-101 uses the same proprietary connector for the charger as for the laptop-keyboard connection.) Wait for the tablet to be mostly charged before reattaching the keyboard.
Might the problem exist with other Transformer-style devices that have a battery equipped, detachable keyboard? I think so. I have a Surface-class Sony tablet with keyboard. The keyboard is separate from the screen (poor design decision) and so needs its own battery to operate and to communicate via Bluetooth.
When we want to recharge the keyboard's battery, we need to stick the keyboard onto the tablet facedown with magnets; no using the tablet when the keyboard needs charging! Three small pins connect power between the two.
When I leave the keyboard switched on when the tablet is off, the keyboard slowly drains its battery, causing the tablet to recharge it, causing the tablet's own battery to drain.
In this case, the design is one level better than on the ASUS, as the power supply plugs into the tablet, instead of the keyboard. The tablet get recharged before the keyboard.
However, this means that when the keyboard is dead, and so when I need access to a keyboard, I have to use the on-screen keyboard or plug in an external keyboard.