Refer Silicon Chip Magazine January 2008
This easy-to-build project is designed to automatically supply power for 12V emergency lighting during a blackout. The system has its own 7.5Ah SLA battery which is maintained via an external smart charger. The system includes a manual override switch and automatic protection to prevent over-discharge of the battery. Build your own emergency lighting system so you won't have to search for candles or your torch in the event of a blackout. Kit supplied with all electronic components, screen printed PCB, front panel and case. Charger and SLA battery available separately.