Making Charcoal

Much of the time is related to scale - a one gallon paint can in the barbeque might well get done in under an hour, and a gigantic killer pile might take 3 days or more.

Your basic small-scale method is to put the wood to be charred in an almost-sealed can and cook it. Your smarter or more efficient methods arrange the non-sealed portion to vent the steam, and eventually gas, in such a manner that once the gas (from the cooking wood) gets going you don't need any more external fuel to cook it - the gas coming off the wood is used to cook it.

Here is a nice explanation on a slightly larger scale - scale down to fit your needs...

I make my charcoal in 45 gallon barrel. The time it takes to make it ranges from 3 to 5 hours from start to finish depending on how green or wet the wood is. I average between 2 1/2 and 3 buckets full of good charcoal per burn.

I'll second the method Ecnerwal posted.

I've used it, although not to that scale.

If your wanting to make charcoal, make as big a batch as you can stand each time. I'm guessing your wanting to burn it in your forge? If so you can go through it quite quickly.

For small batches I've used an old cookie tin with afew holes punched in the bottom. just fill it pretty tight with some small pieces. I stacked mine vertically. set it in/over a good fire for afew hours.

I've used the smaller batches for charcoal "fuel" for small fireworks.