Acer Aspire A515-51G charge switches on and off while plugged in after 50% charge is done.

I'd say the problem has to do with the battery, how long have you had the laptop for?

Batteries are made of cells (commonly 3 nowadays), which is where the energy is stored, and associated circuitry. That circuitry is in charge of reporting data to the machine, making sure the cells are not completely discharged (or over charged), etc.

As they're charged and discharged, cells deteriorate and they lose capacity over time. In other words, they're able to hold less energy compared to when they're brand new (and so the battery lasts less). That's what the battery wear represents, it's a measurement of how degraded the battery is.

It may not be accurate, the circuitry inside the battery may report wrong data. For example, the machine may think the battery is still charged when it's not and suddenly power off. Calibrating a battery is a way to make the controller report more accurate data, traditionally at least, I don't know where the current best practices stand in regards to it (generally speaking, fully discharging a battery repeatedly is bad for the cells, just like extreme heat). The system would then work with that data when estimating how much time is left when running on battery or which charge % it's at.

After all this preface, a battery wear of 50% implies the battery is able to hold half the charge it could when it was new. It could be age related if that laptop has been in use for a while (say a year or two, degradation depends on usage), it could be a bad cell (the others being in good condition), maybe even a busted controller inside the battery (it's not doing what it's supposed to be, it's damaged somehow). It's hard to tell without examining the battery.

The cause of the problem you're experiencing could also be the charging circuitry in the motherboard, a short or a dying component could result in interrupted charging; but my money is on the battery because failures there are way more common.

If your laptop is still on warranty it may be interesting to contact Acer and see if they can take a look at it. If the battery needs to be replaced and the problem is not in the motherboard it may not be covered by the standard warranty, some manufacturers don't include batteries because they're expected not to hold enough energy at some point.

If it's not on warranty, an option would be to buy a replacement battery (I don't know if Acer sells them directly, cheap 3rd party alternatives are usually subpar to put it mildly, they last less) and replace it yourself. It may sound daunting, but I'm sure there are video guides for your model on YouTube for example (the general gist is unscrew the back plate, disconnect the battery connector, take it out and put the new one in). It's not difficult .

BlazinGirl said:

I said "maybe" which is probably a no...

That made me giggle

Best of luck!