Trustfire charger humming

[SunnyMoon]

I bought a Trustfire dual multi function charger for my Trustfire 18650 batteries. I've had it for less than 2 weeks. When I plugged it in this morning it started making this high pitch humming sound, so I immediately unplugged it.

Granted this was the first time I've used it without having a fan or the AC running so it may have always made this sound but I wanted to ask everyone here if this is normal for chargers.

Just to note, I have the batteries in the charger with the correct polarity. I have 4 batteries, 2 are a few months old and 2 are less than 2 weeks old, but since they are the same kind I don't know if the old or new ones are in the charger. Which brings me to my second question, when you buy new batteries, do you mark any of them to tell the difference between the new and old? I only bought the new batteries to have more of them, I did not have an issue with the old ones.

 

[Optimo]

I bought a Trustfire dual multi function charger for my Trustfire 18650 batteries. I've had it for less than 2 weeks. When I plugged it in this morning it started making this high pitch humming sound, so I immediately unplugged it.

Granted this was the first time I've used it without having a fan or the AC running so it may have always made this sound but I wanted to ask everyone here if this is normal for chargers.

Just to note, I have the batteries in the charger with the correct polarity. I have 4 batteries, 2 are a few months old and 2 are less than 2 weeks old, but since they are the same kind I don't know if the old or new ones are in the charger. Which brings me to my second question, when you buy new batteries, do you mark any of them to tell the difference between the new and old? I only bought the new batteries to have more of them, I did not have an issue with the old ones.

This is normal for this charger...there is nothing to worry about. Mine does it all the time and has never did me wrong in 2 years.

 

[CATastrophe]

As for batteries, I keep track of mine by putting the date I received them on them. I just write it on a little bit of paper and tape it to the batts. I also meter them frequently before going on the charger and when coming off. I use an Ultrafire 139 charger and on occasion have heard a very slight high-pitched hum when charging. I've never had any trouble with it, though.

I don't plug and unplug it all the time, either. I have it on a multiplug with its own on and off switch so that is what I use to turn off the juice to it when I'm not using it. I also never leave batts to charge overnight or when I'm not home.