Battery drops from ~35% to 0% instantly

[ashik762]

The J7 Prime is really old -- released in 2016, so it's 9 years old. If it's the original battery, it wouldn't be surprising that it's failing. But even if you replaced the battery, there's a good chance that replacement battery is also old and degraded, since it may have been sitting on a shelf for years.

It is own orginal

 

[B. Diddy]

That's your answer, then. It's a 9 year old battery. With normal usage, most batteries have degraded significantly by year 4 or 5, so at 9 years, it's not surprising if it can hardly hold a charge or has other odd behavior. You could look into replacing the battery (again, with the caveat that replacement batteries will probably also be old and degraded), or upgrade to a newer phone.