replace batteries with power supply using USB cable / smartphone power supply

I am trying to replace the 4 AA batteries inside an IKEA STOTTA motion detection light with a power supply in order to make it more stable actually. Batteries tend to slip out of place and it doesn't work when needed. Plus the fact that my dog makes it go off every now and then wearing out the batteries.

Since 4 AA's are 6V i figured it was worth the while to try if it would work with an old iPhone USB charger plus USB 1.0 cable and it worked! Now I only need to figure out how much current this needs so that I do not blow up the charger. Is there a way to measure or assume by the 4 AA's how many milliAmps the USB power supply should be rated at? The only thing I know about the LED itself is that it is 30 lumens / IP44 / 2700K / 25000 hours as per the e-shops' product description.

Any help would be greatly appreciated.

Hi!

I think you have nothing to worry about. The current your light needs will most likely be around 100mA. Any USB charger should deliver that. Also don't worry about overloading them. Chargers are by law required to be overload-proof. I tested this with 3 very cheap chinese USB chargers, and each of them lowered the output voltage when I approached the rated current.

Agreed. If the LED is only 30 lm, it won't even be close to overloading the charger.

I've had a very positive experience with these.

No batteries/special adapter required!

Thank you all for your feedback! You gave me enough to go ahead with this. Once I get some mains voltage close to the mounting spot, I will let you know how it performs.