Which problems can be expected by continuing to use a MacBook Pro Battery already due for replacement? I turned in my MacBook Pro 15" Late-2013 to a service shop. The battery indicator recently has said either "Condition: Replace Now" or "Condition: Service Battery" (I can't remember which).

The service shop returned a service cost proposal: after currency conversion $350 USD + VAT including work. Quite expensive.

The reason for the high price is – according to the shop – that the battery on this model is permanently attached to the so called "Top Case" (unibody case + keyboard + trackpad). To replace the battery, the Top Case assembly must be replaced.

I am inclined to reject the service offer, and keep on using the computer with the current battery. What sort of problems can be expected by doing so? Is the computer in any danger in the short or long term?



FYI, MacOS help about battery conditions:


  View your battery’s condition: Press and hold the Option key and click
  the battery icon  in the menu bar.
  
  You may see any of the following conditions:
  
  Normal: The battery is functioning normally.
  
  Replace Soon: The battery is functioning normally but holds less
  charge than it did when it was new.
  
  Replace Now: The battery is functioning normally but holds
  significantly less charge than it did when it was new. You can
  continue to use the battery until you replace it without harming your
  computer.
  
  Service Battery: The battery isn’t functioning normally, and you may
  or may not notice a change in its behavior or the amount of charge it
  holds. Take your computer in for service. You can continue to use your
  battery before it’s checked without harming your computer.
I use a similar model of MacBook Pro (15” Late 2013).

The batteries have something called charge cycle (1 charge cycle = 1 full charge and discharge). The MacBook Pro battery typically retain 80% charge holding capacity after completing 1000 cycles.

Although the advanced lithium-ion batteries in MacBook is meant to last for several years before they begin to lose their overall charge capacity, there will eventually be a time when it will need replacement.

This is reported by macOS by alerting you about battery condition. You can also view the current cycle count of the battery by going to Apple Menu → About This Mac → System Report... → Hardware → Power → Battery Information: → Health Information: → Cycle Count.

There are also various 3rd party apps which you can use to determine the current battery health status. coconutBattery is one such popular tool.

Once you are convinced that the battery need replacement, it is strongly advised to do so.

Also, the top case, keyboard, trackpad and the battery comprise of a single unit in the MacBook model you own. The entire unit will need replacement. (I got mine replaced a few months ago). That explains the hefty price tag.


  Which problems can be expected by continuing to use a MacBook Pro Battery already due for replacement?


Continuing to neglect replacement may end up damaging other components thereby leading to more expenses. In my case (pun intended :-D), the battery started swelling which could have also ended up damaging the logic board assembly.

Other obvious issues include, lesser backup than expected, random shutdown under load and possibility of reduced performance at times.

If you haven't done so in the last 5 years since you bought the MacBook and macOS is alerting you about it, it's highly recommended to get the battery replaced for extending the lifetime of your MacBook Pro.