Hi all,
I've recently been faced with the same dilemma about what to do to keep an old MacBook Pro powered when not near a wall socket. Mine's the last 17" model produced (2011), souped-up with maximum RAM, a fast SSD, a dGPU bypass, dual-boot with Ubuntu, etc. etc. It's still a great machine with a fantastic selection of ports that I still find useful… but urgh isn't trying to source a reliable replacement battery a pain?!
So I thought I'd share my experiences in case they help anyone else. In August 2016 the original OEM battery started swelling, so I paid Apple to install a new battery, which of course worked great for several years. However, in 2022 I started to get a bit nervous about the potential for the battery to fail so when I saw a UK supplier had a NewerTech battery in stock for a good price I grabbed one to have in hand ready for when I decided the 2016 Apple battery was no longer usable.
That time came late 2023 when the laptop started conking out randomly when running on battery power – I guess the ageing battery was no longer able to supply the right level of power consistently so if the laptop needed to draw a bit more for a few seconds, the battery would struggle and the whole system would switch off with no warning. So I swapped in the NewerTech battery and… hmm. Not great. Several observations struck me during installation and after subsequent use:
- The plastic battery casing was thicker than the OEM battery, causing the bottom body panel of the MBP to bulge slightly when screwed back on, and causing the trackpad to feel and sound slightly different.
- The battery was completely dead on installation – not even a blinking single green light on the battery gauge.
- Probably connected to that, when calibrating or otherwise draining the battery, it would never safely shut down or hibernate when the battery was low – it would just die, like pulling the plug on a desktop, and even the computer's clock would reset if left too long without plugging in.
- After calibration the battery would work well down to about 20/30% but then speed down to under 10% before collecting its thoughts and dropping more slowly again. Severe CPU throttling would kick in around about this point too. I never like to use the laptop 'til the battery's that low so that meant I was only effectively using three quarters of its capacity. (This, incidentally, has shades of the OP's iFixit problem and others who've observed batteries dropping quickly to 7%…)
- After a few months that problem problem would get worse (e.g. it would start dropping quickly from 40% rather than 30%) and would have to be resolved by recalibration.
- The battery's controller was clearly not actively measuring the usable mAh capacity, because it stayed at the same value for a long time and then would drop precisely 5mAh every time another cycle was added to the tally. (Compare with an OEM battery, whose usable capacity fluctuates up and down constantly.)
The one positive to say is that if successfully working around all of the above, the battery did seem to provide a good amount of total usable capacity… it just wasn't very easy to use reliably. (By the time I realised its various flaws it was too late to request any help via the warranty, unfortunately.)
Anyway, fed up with all of those niggles and having read a number of good reports here and elsewhere about 2-Power batteries, I decided to try one of those recently, ordering from Duracell Direct. Sadly, there's no great news to report from that either. The plastic casing is identical to the NewerTech, the battery still exhibits the same behaviour around the 10–30% mark, and the mAh reporting is still untrustworthy. It does die gracefully however, so that's something. It is also, interestingly, much lighter (by about 100g!) than the OEM and NewerTech batteries, so maybe it's made with newer, lighter-weight cells similar to more modern laptops.
I have decided to give 2-Power another chance though, by requesting an RMA and a replacement – partly because being in the UK, this seems to be the easiest recognisable brand to obtain on an ongoing basis. Duracell Direct have been very apologetic and seem keen for me to have a properly working battery (which I will define as being one that drops from 100% to 0% evenly and consistently without much throttling), so we'll see how my next go on the battery lottery plays out. If it's still not satisfactory I'll request my money back and try one of the other battery brands
f54da's research highlighted.
Finally before everyone's completely bored to sleep, I'll add that I've produced a very rudimentary shell script which I run in Mac OS X Recovery to calibrate and test/log the battery's performance whilst calibrating. It works by cycling between a few seconds of a simple single-core CPU process (a specific number of iterations of ‘echo y > /dev/null’) and several more seconds of idling, timing how long it takes to do this for each cycle so it's possible to see when throttling has kicked in (because the time to do the ‘echo y’ CPU work increases). These are the results for the three batteries in my possession:
| Brand | Purchased | Manufactured | Capacity | Full perf. time | Throttled time | Total time |
|---|
| Apple | 2016 | 2016 | 85% | 4h 26m | 0h 17m | 4h 43m |
| NewerTech | 2022 | 2020 | 94% | 4h 13m | 1h 18m | 5h 31m |
| 2-Power | 2025 | 2024 | 102% | 4h 11m | 1h 09m | 5h 20m |
| 2-Power | 2025 | 2024 | 102% | 4h 47m | 0h 38m | 5h 25m |
So the battery providing the longest unthrottled performance is… the 9-year-old OEM battery!!
Edited 2025-04-29 to add manufactured dates, and results from second 2-Power battery.
