The jailbreak itself doesn't drain the battery, it's the stuff you install via Cydia that does. Start removing things you installed until the battery returns to normal.
If you have an iPhone 4s did you restore from backup? If so that could be the problem also. Set it up as new. It's a pain bit it's good to start fresh.
If you have an iPhone 4s did you restore from backup? If so that could be the problem also. Set it up as new. It's a pain bit it's good to start fresh.