I was using 1.7 before 1.8 came out and battery usage was not great on it even though supposedly it had baked kernel #6 which was best in battery usage. When 1.8 came out I tried it and battery was the same. I then flashed #6 kernel on top of it and battery usage drastically changed. With stock 1.7 or 1.8 after taking the phone off the charger in the morning, the battery immediately drops to 99% and within a few minutes would be down to 95%. By the time I got to work (10-15 min later) the battery would be down to 90-91%. But with kernel #6 on top of 1.8, it remains at 100% when I take it off the charger and when I get to work it is at 99%. I'm going to assume flashing #6 on top of 1.7 would yield the same result. So that may be your next route.