3.12.2014

This battery powered LED-light is really useful.
We use it in an old house, where appropriate light switches are rare. E.g. the entry hall with 6 doors in total has only one light switch.

Now i have 6 pieces of them installed and I have to change the batteries (3 pieces Sanyo Eneloop AAA, 750mAh) in one of the devices nearly every day. So I measured the current consumption:

Light on: 48…50mA @ 3×1.40V
Light off, approximation sensor active (in dark environment): 300uA
Light off, approximation sensor inactive (in bright environment): 60uA

When we assume a dark installation site, where the AS is active all the time, the batteries should last for about 104 days. When the Light is on 1 hour per day, it should still last 13 days. This seems to be quite realistic. I think, in the average, my devices last for about 10-14 days.

Sadly, no deep discharge protection is implemented. The Light gets weak, when one of the batteries goes below 0.9V, since the impedance of this cell increses.
Once I measured nearly 0V of one NiMH cell, wich is not good. Hopefully the cell recovers. For now, I'm measuring every cell voltage before replacing it with freshly charged ones.