If you need a good solid battery light for dark roads up to about 15MPH I like the Planet Bike Blaze. I’ve got the 2 watt model and it’s plenty bright for riding down a back country road. The “Super Flash” feature during the day really gets you noticed too. Runs about 50 bucks or so.
Probably the best Self-Contained light for battery use would be the Busch & Muller Ixon IQ. Not cheap, the light without Rechargeable batteries (AA) runs about 115 bucks. Super bright, rectangular beam, made by Germans to meet their laws. You can find it at PeterWhiteCycles.com.
If you want something that will really fill the road with light and are willing to go with a separate dedicated battery pack I’d say the Magicshine Lights. Are a good value for the money.
Hope this helps.