Is my MacBook battery a ripoff?
April 27, 2011 12:28 PM   Subscribe

Is this laptop battery a ripoff, and how can I be sure? I bought a third party battery for my Macbook. It looks like the original 45Wh battery, but Coconut Battery (and the appropriate ioreg command) report the 'design capacity' as lower than it should be.

The third-party battery says it is 45Wh, but it reports its 'design capacity' as 3600mAh. 45Wh at 10.8V should be ~4100mAh, and the original battery does indeed report a 'design capacity' of 4100mAh. So the new battery seems out of line.

Note that I'm not talking about the current capacity here. I'm aware that the current capacity will be different from the design capacity, and that it can be fixed by recalibration. But I would expect the design capacity to match the value stated on the package.

So, is this enough evidence to send the battery back to the seller for a refund? Is there another way to be sure whether I got what was advertised? And are third-party batteries often sketchy in this way?
posted by beniamino to Computers & Internet (10 answers total)
Third party batteries are often sketchy in this way. I had two for my late lamented MacBook Pro, and they both had weirdness when it came to capacity and reporting.
posted by infinitewindow at 12:54 PM on April 27, 2011

Is the new battery lighter than the old one? Maybe it has fewer cells, and thus less capacity.
posted by scruss at 1:01 PM on April 27, 2011

I bought a knockoff battery for my old PowerBook for $40 (as opposed to $120), and it reported as having twice the charge as it actually seemed to, and only lasted for a year. This is just anecdata; I don't know anything about the technical specifications.
posted by soviet sleepover at 1:10 PM on April 27, 2011

I don't know about technical specs, but I have yet to find someone who was actually happy with their knock-off replacement MacBook battery. I bought an Apple replacement for my recently departed Macbook, and it was three years old and at well over 700 cycles (886 sticks in my head, but I wouldn't put money on it) and 95 percent health when I finally overheated and killed the logic board.

The same goes for knock-off cell phone batteries, at least in my experience. With Li-ion batteries, it seems that you get what you pay for.
posted by rockindata at 1:20 PM on April 27, 2011 [1 favorite]

I bought a battery from OWC for my MacBookPro last year for about $45. It was part of a batch that OWC had been mislabeled or something in the firmware reporting wrong or some such. I didn't really understand but couldn't afford a new battery from Apple (or even the $100 regular price on a third party battery) so took a chance. It has been working fine so far. Fully charged it offers about 3 hours of life. I think it has fewer cells than the original, but it does work well. I see things in terms of hours/minutes and not mAh. Because of the cryptic description from OWC, I didn't even bother looking at mAh on this.
posted by birdherder at 1:23 PM on April 27, 2011

I bought a battery through Amazon that the vendor claimed was OEM. It wasn't: The labels were made up of different typefaces, making it a dead giveaway. The battery cells bulged out of the enclosure. I sent it back, gave the vendor bad feedback, and promptly bought a real laptop battery.
posted by Blazecock Pileon at 1:36 PM on April 27, 2011

Not the same but still Apple related: I bought a "double mAh capacity" battery for my 5th generation iPod classic a few years ago off of eBay. It was bigger than the stock iPod battery, and cost something like $10.00. The mAh capacity was not double (more like the same). Caveat emptor if you're planning on cheaping out your replacement MacBook Pro battery.
posted by JesseBikman at 1:41 PM on April 27, 2011

Run it until it discharges and see how long that goes. Compare to when the old battery was new.

(Also compare the voltage from the old to the new. Some computers are designed to be able to take batteries of different voltages, and that's how they sell batteries of different capacities. The standard battery might be 10v and the extended one might be 14v. Or vice versa. Depending on conversions inside the computer, you could get equal performance out of a battery that has a lower mAh rating.)

There is some confusion/lying that goes on with mAh reporting in batteries. This is partially because batteries aren't linear. If you take a 35mAh battery you should be able to draw 35mA off of it for an hour, and then it is completely discharged. (Or 70mA for a half hour, or 17mA for two hours.) But it doesn't really work like that too much.

Different manufacturers and industries test and report different ways. The fewer amps you draw, the longer it will run. So, Apple might have rated the original battery at 45Wh by running the laptop until it dies, while measuring how many watts the machine consumed during that time. Whereas the battery cell manufacturer might have a standard 2 hour test that they run. The cells might get the same ratings, but the one that had the higher drain/shorter duration test will actually power the laptop longer.

(I just bought a car battery, for example. It says it has 1000 cranking amps. But those are like amp-seconds.)
posted by gjc at 5:05 PM on April 27, 2011

> Run it until it discharges and see how long that goes.
> Compare to when the old battery was new.

I dunno why I didn't think of that before. Sure enough, the new battery actually lasts less long that the old one I was replacing. I think I will ask for my money back.
posted by beniamino at 6:38 AM on April 28, 2011

Before you give up, re-charge the battery to full and time the discharge again. The battery may not have been initially calibrated so that the first cycle was not a full charge even if the charge indicator said it was full. Discharging completely and then re-charging should recalibrate the battery.
posted by JackFlash at 9:15 AM on April 28, 2011

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