Some time ago I attended a Remy Martin Cognac tasting and at the end of the night, we were given mini-kegs to age anything we liked in it, Cognac or another drink. The kegs were new oak and charred black inside.
The keg sat unused for quite some time, but finally I dumped a bottle of near-white dog in it. It was a rye mash whiskey from a craft distiller which had been given 3 months aging in a small cask before sale.
When I put it in, the whiskey was light yellow. I put the little keg in a straw basket (oblong, planter-type, it happened to fit snugly) and left it on the balcony from later June until now.
In the first two days, an appetizing smell arose from the keg as the liquor soaked in - very similar to a bourbon warehouse.
The temperatures probably swung between 60 F and 95 F at various times, with of course nights generally on the cool end of this.
I tasted it after a month, and now again. It has improved each time. The colour now is quite dark, like any good 8-12 year bourbon. The taste is half way to a good bourbon or rye: it still has some taste from the white dog and perhaps from the first cask it was put in. Like many craft whiskeys given some age, it had a piney, spruce-like smell, and I've never been sure if that is from insufficiently seasoned small casks or from short aging in any new charred wood no matter the size. Anyway the piney taste is diminishing, but it's still there partly. I will leave it out a couple more months but finally will have to take it in because it will get too cold in Toronto to leave it out there. It was 80 proof, so could freeze. However, a couple more months may "finish" the aging, or close enough for me. I am quite happy with this experiment, and can see that in a keg of any size, charred and new wood, you will definitely get improvement even if it won't replicate completely the slow oxidative changes of normal barrel aging.
It's pretty fair now actually.