I have an old (ca. 10 years old) 6V lead-acid battery and a mains charger for it and I know the combination worked years ago.
Now I tried to recharge the battery and the charger's LED turns on during charging, but when I use the battery with a LED bicycle light (for dynamo use) the bicycle light doesn't illuminate. Of course the light might be defective, so my question is:
How can I check whether the lead-acid battery and its charger are still working?
I do have a simple digital multimeter and after charging the battery over night it gives me a voltage of 4.5V at the battery (no other load attached,) but at the plugged-in charger I see strangely only 0.15V (no other load attached.)
I have no idea what's going on. Is all of this normal and the bicycle light is the problem?
The battery is a DiaMec SLA battery. Here a picture of it:
And the brand of the charger is PowerTech:
Update II / Resolution:
Finally, after reading all the great tips and comments, I did get a new battery (exactly same make and model) and the old charger works perfectly with it and the lamp works as well. So indeed, as people told me, it was the battery which was defective.