IKEA SUNNAN - battery pack

Having a look at the inside. Charging at overcast conditions takes quite a while. Therefore I decided to charge the batteries externally, so I'd have a chance of observing the full LED brightness much sooner.

Solar cell data:

5.78V, about 50mA short circuit current using an artificial sun. That would take a bit more than the advertised charging time of 12h, but ideally the sun is stronger than that light bulb.

One thing I've had to find out is that not every battery fits properly. I tried the ones from my bike light, which nominally are AA as well, but they don't get proper contact. The green body of the ones in the picture is about 1mm shorter, but the distance between back and front contact is the same.