Rechargeable batteries for sensor light

[Ian Osborne]

My partner and I have bought a sensor light, the sort that comes on when it's dark and movement is detected, then switches itself off 30 seconds after everything is still again. The cheapo batteries that came with it lasted around three weeks, which isn't bad, but when we tried rechargeables in it they barely worked. We used Ni-Mh AA batteries, 1300 mAh. Is this the best sort? It's not a powerful light and it's only on for a minute or two an evening. The light itself recommends 'UM-3' batteries. Is this a specific type, or just the American term for 'AA'-sized cells?

 

[richardm]

UM-3 is the same as AA. Is it a halogen bulb? Perhaps you need beefier batteries to get that fed. You might actually do better asking this in the Science forum, it gets a bit more traffic.

 

[Charlie in Dayton]

All men are created equal, but all batteries aren't...I've recently been working with some equipment where battery life is a factor, so I already had most of this looked up and bookmarked...

Alkaline batteries at full charge deliver 1.5 volts. NiMH (Nickel Metal Hydride) batteries at full charge deliver about 1.25 volts.
Alkalines are designed for long shelf life (anywhere from 3-5 years), and low current constant drain applications (radios, LED lamps).
NiMH's are designed for high current intermittent applications (camera flashes, CD players), and have a short shelf life (1-2 months before recharge is required).

Alkalines are not readily rechargeable. NiMH and NiCd (Nickel Cadmium) are designed to be recharged.

See here and also here for further info.