Replacing battery on MacBook Pro mid-2012
After 5 years, you expect to change the batteries and the operating system even gave a warning that the batteries were wearing out.
Ordered my battery from another firm initially, but used the iFixit tools and directions.
All went smoothly in the disassembly until the part where you remove the batteries themselves, which are glued in for this model. That's when we discovered the new batteries we received were defective (first time we opened the package). So we carefully photographed the defective unit for documentation and called the vendor. They kindly gave us a full refund after looking at our photos. We promptly ordered an overnight rush on the battery from iFixit because we didn't want to chance another bad unit. That's when we learned that Lithium batteries can no longer be delivered overnight (ground only) due to new airline regulations. So we had to wait 4 days for delivery.
Removing the old batteries was a pain (expected). One surprise was that we didn't have the removal fluid that iFixit supplies, but we learned that a $0.93 bottle of acetone from the drug store plus a $1.75 syringe was a good replacement. [Note: we did the ungluing while waiting for the iFixit shipment. When the iFixit shipment arrived, we discovered it came with the acetone and other tools (superfluous to our existing toolset).
It took quite a bit to get the glue to come loose. We were very concerned about getting acetone in the wrong places. Despite our fears it went well.
Also the some aspects of the replacement batteries did look identical to the old ones (some bits of plastic that were somewhat superfluous in the original). That had us wondering about the parts or instructions for a few minutes.
Order your replacement batteries early and check the contents upon arrival. I would also highly recommend using iFixit for your source.