When to know It's time for a new Mac Battery

On those older models, when the battery is not connected, then it makes it a bit tricky to power on the laptop. Sometimes you must press the power button multiple times, or even hold the power button in for an extra second as well.

Sometimes a bad or depleted battery will prevent the laptop from powering on. Disconnect the battery and see if it makes any difference keeping in mind what I wrote in the first paragraph.

Unfortunately the quality of third party Lithium batteries is extremely poor even when purchased from a respected vendor such as OWC or iFixIt. These two vendors would be the only ones I would trust to purchase a Lithium battery for this laptop. So many other vendors online actually sell batteries with only a single cell which is worthless except to provide a very short runtime in the event of the Magsafe connector coming loose and to prevent the system from running the fan(s) at high speed.

Apple stopped recommending battery calibration after they moved away from quick-detachable batteries about 2009. Deliberate and excessive running to zero as required by outside calibration instructions can degrade the battery.

For batteries, Apple considers 1000 cycles a life well lived. You can see your cycle count by running System Profiler/System Information in your Utilities folder and selecting "Power" in the left-hand Contents pane:

Allan Jones wrote:

Apple stopped recommending battery calibration after they moved away from quick-detachable batteries about 2009. Deliberate and excessive running to zero as required by outside calibration instructions can degrade the battery.

Yes, for Apple OEM batteries. However, third party batteries usually have a note to calibrate them. We recently had a third party battery from iFixIt where it the battery was not properly calibrated & it ended up having some issues. Hard to say if it was from not calibrating it or if it was defective from the start.

However, from my observations, I think these third party Lithium batteries do need to be calibrated if for no other reason than a gentle exercising of the cells until after the first full charge cycle is completed. I think it is worthwhile to first charge the battery to 100% and let it sit there for a few hours. Then slowly drain the battery until it reaches 0% and powers off the laptop. Reconnect the power adapter (don't let it sit for too long) and let it charge back to 100% and once more let it sit for a few hours. After that use the laptop & battery normally. Definitely the battery should not be left completely discharged for any extended length of time.

Calibrating may be a poor choice of terms here as it may not have quite the same effect as on the older NiMH batteries. I think it is the gentle exercising of the Lithium battery that is important here. I saw signs while monitoring the new third party Lithium battery that this is likely needed. I haven't seen the same behavior with an Apple OEM battery replacement.