Bought a new battery and OSX started showing Service Battery already! How to solve

Try a SMC reset:

https://support.apple.com/en-us/HT201295

Many third party batteries are very inferior counterfeit knockoffs and you might be a victim of one of them. The only third paryt batteries that I can recommend based on actual experience by others and myself are Nupower and Anker.

Sometimes a battery is simply defective, regardless of the source.

Ciao.

What does System information (SI) say about the new battery. Access SI from the "About this Mac" window's "System Report..." button, When SI opens select "Power from the left-hand contents pane. It wll show numerous data point for the battery.

For your battery, copy and paste the lines I've highlighted in the image and paste your results in a response to your own thread.

Did the battery come in a Apple-branded box? If so, its a fake; Apple has never sold replacement batteries for notebooks like yours whose battery that consider "non-user serviceable" except to authorized service providers who install them. Apple expects you to have them replace the battery at an Apple Store. If the battery came in Apple packaging I would notify Amazon of their trade partner's fraudulent practices.

Many bogus batteries have the same serial number: 0123456789ABC. The serial number may appear in the SI report.

It is possible that a third party new battery can be bad, if it has been sitting in a warehouse for the past several years. With batteries for older devices, that is often the case - the battery is retail new in that it was never sold, but it has been sitting on a shelf for years, steadily decaying as it sits. Lithium batteries die whether used or not.

Did the battery itself have a date of manufactur on it? You should be able to get a refund or exchange through Amazon if it's faulty. But it is always problematic buying lithium batteries for old equipment off the web. As Ogelthorpe says, many are just plain poorly made batteries to begin with. And many others are simply very old warehouse stock that some seller picked up cheap.

That battery is simply a dud. Since it is not even a year old, you should contact the seller.

1guilopes wrote:

And after I turn back on the date and time become a mess and I have to reset all over again.

If the date and time on the MBP is being reset, that is a sign that there is a disconnect occurring with the battery. That is unacceptable. I would be looking for a replacement from a different source.

Ciao.

The issue that you are dealing with is not going to be defined by coconutBattery. There was an electrical disconnect either in the battery or in the MBP (evidenced by the date/time reset). Perhaps an Apple Hardware Test will provide a clue:

https://support.apple.com/en-us/HT201257

Note that an error free AHT is not conclusive.

Ciao.