Chrisbood has a valid point. The voltages, and their tolerance level, differ depending on the charger and the connector (cable). I have seen "dead" phones come to life when an appropriate voltage was applied via USB. It doesn't have to be USB. The point is that a computer acts as a voltage regulator in a sense. It queries the driver for device information and supplies the necessary volts. So a good first step with any phone that appears dead is to change things up. If you have it plugged into the wall and you get nothing, try plugging it into the computer with the USB cable that came with it (or another power source that supplies similiar voltage).
If that doesn't work, then your are faced with a dead phone unable to run software that people have suggested here. What do you do?
If you are planning on providing your old phone to a non-profit that will strip it apart anyway, why not pre-strip it? By this I mean that you can pull the memory chip off the circuit board. If this makes no sense to you, then please don't bother trying the next step. (unless you want to learn)
The memory chip is very obvious on most PCBs (the electronic board that all components and wires plug into). Do a Google search for your model first and foremost. With any luck, someone has already gone through the dificult stuff and laid it out in steps.
Once you find the RAM, then you can simply remove it. WARNING: This will leave your system inoperable! Only do this if you know that the recipient is going to strip it.
Once you have the RAM, it is up to you. You can put it in a safe or smash it with a hammer. Either way, when you have eliminated memory there is nothing that a computer can do, currently, to extrapolate any kind of information.