Even 300W is a lot to put inside a small box and expect to keep cool with a computer fan. It's just not good engineering practice to put a big heat source in an enclosure if you can avoid it, and I wonder how many other people are doing this.
If it weren't for the mental image of a house fire caused by trying to nurse a hybrid battery into better health, I wouldn't be nagging so much. But having said my piece, I'll stop and let you do what you wish. Good luck.
