Emergency Workshop Lighting - V1.0

After testing some Li ion cells I realised how useless those Chinese sourced 18650 cells can be. As the pile of cells grew I wondered what I could do with them. 

It dawned on my one evening as I closed up the workshop that there are times when a sudden power outage could leave me vulnerable when exiting the dark workshop. I had previously made my own flashlight with high intensity white LEDS for those frequent nigh-time excursions to the toilet. 

So I combined my CC/CV charging standard with a white LED driver gave me a box with plenty of light to safely exit.  I used some diode bridges so I can use any 8-30V mains derived AC or DC power source and a pass through design so lights can be daisy chained. I ended up installing three such lights across my storage bays and as soon as the power is lost the lights turn on for 10 minutes. Plenty of time in my workshop to turn everything off and exit safely. 

If the power comes back on within the 10 minutes they turn off and start recharging. Otherwise they turn off and wait with a mosfet isolating the battery from the current drain of the charging circuit when no power is present.

So in hot weather I simply turn off the power. A broad estimate is a current draw of 100mA from the battery when running. That's means even the rubbish cells I fitted will give over an hour of light knowing that the batteries will slightly discharge for 10 minutes before going into near total shutdown. The micro, being asleep most of the time, consumers very little current so I expect that the lights remain in a good to go state. 

In practice during summer I expect I will turn them on for perhaps two hours a week in the cool of the morning when I can "escape" to the shed while it is relatively comfortable to wield the soldering iron. 

The next version will have a switch fitted to allow for manually turning the light on and off during power outages when I may need a lantern. A shift to better batteries is also planned which will allow for both a longer run time and still brighter lighting. No point half-doing something.