Explorer Hat Rev 0 Charging Light Modification

This modification applies to first generation Explorer Hat boards, shipped April and June. 

Some of our first Explorer Hats have a minor problem you should be are of. This page will tell you what the problem is and what your options are to resolve it.

How do I know if my board has the problem?

If you try to charge a full battery, or leave your battery charging overnight, then the charging LED will never turn off.

What is the minor problem with the first Explorer Hats?

We designed the red charging LED to be lit when your battery is charging, and to be off when your battery is full. That's not what's happening on the first set of boards that we shipped out. While annoying, this does not effect the ability to charge a battery or the safety of the product.

Technically speaking, what is the problem?

One of the transistors (Q3) wasn't chosen properly. This transistor is distorting the LED control signal, causing the LED to stay on whenever USB is plugged in.

What is the fix? 

The Q3 transistor needs to be removed. This is a transistor that's in the corner of the board. It's a little 3-pin device near the RPi header (you should be able to spot the "Q3" label).

If removing Q3 fixes everything, why is Q3 there to begin with?

We originally planned to use Q3 to allow the RPi to tell when the battery was done charging. That would have taken some software changes that haven't been done yet. By removing Q3, the RPi will not be able to tell when charging is done. You'll have to actually check the LED.