I cannot understand what has happened but I have a single 18650 mains operated battery charger which I've used for several years to charge the 18650 battery in a LED torch. Whenever the battery needed to be charged I would of course place the battery in the charger with the positive end of the battery towards the positive connection pad and toward the + sign in the charger and negative against negative against the negative spring.
The battery needed charging the other day so I placed the battery in the charger as I do and left it to charge but the green LED light remained on as if the battery was already charged. I tested the battery with a multimeter and the battery only had a few mVolts. So I placed the battery again in the charger. After about 12 hours and with the green light constantly on, I took the battery out but again the battery had no charge. I couldn't work this out.
I then tested the charger and the positive terminal is now negative and the negative terminal is now positive. I placed the battery in the charger the other way around and the red LED came on and after 12 hours the green LED was on and the battery is now fully charged and usable.
The charger shows about 4.2v on a multimeter.
Why has the positive and negative terminals of the charger now got themselves reversed?
The battery needed charging the other day so I placed the battery in the charger as I do and left it to charge but the green LED light remained on as if the battery was already charged. I tested the battery with a multimeter and the battery only had a few mVolts. So I placed the battery again in the charger. After about 12 hours and with the green light constantly on, I took the battery out but again the battery had no charge. I couldn't work this out.
I then tested the charger and the positive terminal is now negative and the negative terminal is now positive. I placed the battery in the charger the other way around and the red LED came on and after 12 hours the green LED was on and the battery is now fully charged and usable.
The charger shows about 4.2v on a multimeter.
Why has the positive and negative terminals of the charger now got themselves reversed?