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MacBooks Run Slow Without Battery

By , Amos Ngai - Source: Tom's Hardware | B 22 comments

A new "Power Saving Feature" in the unibody MacBook and MacBook Pros was inadvertently discovered by Gearlog while they were doing a routine benchmark.

Gearlog was benchmarking was to test third party RAM modules for use in the new MacBook Pros, but discovered that the notebook’s processing power significantly decreased after the battery was removed during the test. It was confirmed that Apple does indeed scale back the CPU processing speed while operating on AC power without a battery installed.

According to this support document, Apple essentially down-clocks the CPU to prevent the system from shutting down if it happens to demand greater power than the AC adapter alone can provide: "If the battery is removed from a MacBook or MacBook Pro, the computer will automatically reduce the processor speed. This prevents the computer from shutting down if it demands more power than the A/C adapter alone can provide."

Collaboration from other users can be seen on the Gearlog comments; however, since this support document was last updated in August 2008, I decided to do some independent testing on my own MacBook Pro. I wanted to see if this problem existed in late model MacBook Pros or were they limited to only the new unibody MacBook Pros. Using the same Cinebench R10 benchmarking software, I conducted the full tests three times each with the WiFi and Bluetooth radio disabled and carrying forward the best scores achieved each time.

Performance with batteryPerformance without battery
MacBook Pro performance with battery on left; performance without battery on right.

Gearlog’s own results show a decrease of 36 percent in processor speeds without a battery attached on their unibody MacBook Pro. Our own tests show a decrease of 50 percent when rendering with one CPU, a decrease of 52 percent in multiprocessor rendering, while the GPU suffered a 40 percent decrease in performance.

What does Apple have to say about this? The official statement from its support document is that “It is strongly recommended that you do not use your MacBook or MacBook Pro while the battery is removed.”

The only benefit in operating a notebook without its battery is to conserve charge cycles and thereby extending the battery life. Apple recommends that with notebook batteries, occasional power flow is necessary for its longevity. Standard maintenance is not to constantly keep the battery charged but rather allow it to discharge partially before recharging it again. If your use is infrequent, it is recommended that the battery be completely discharged and recharged once per month.

With such drastic performance decreases on a previous generation Macbook Pro, it doesn’t seem logical to remove the battery when a brand new battery can be purchased for $129 from Apple or possibly even less from other resellers. I would rather have a full powered notebook and a few months less with my battery than the alternative.

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  • 2 Hide
    Anonymous , December 1, 2008 6:48 PM
    Standard maintenance is not to constantly keep the battery charged but rather allow it to discharge partially before recharging it again. If your use is infrequent, it is recommended that the battery be completely discharged and recharged once per month.

    Another bull-shit explenation.
    Li-ion batteries need no discharge, and complete discharge is what destroys them fastest!

    I suggest the person talking about batteries knows not of what he talks.

    Otherwise, strange to see that an apple would do the clockdown.

    It can be prevented by having (or investing) in a more powerfull adaptor!
    I guess that's the cost of saving huh?
  • 1 Hide
    Anonymous , December 1, 2008 7:14 PM
    I've had my Compaq laptop for about 3 years, and the original battery has only decreased in capacity maybe 7%. I can attribute that to removing the battery and using it only so often, while enjoying full processing power plugged into AC. If used in conjunction with a good UPS, there is no reason to have this type of scaling back design. If it's because of the AC adapter's 85 watt output, they should have made a better one, it's not as if Apple makes products geared for the thrifty consumers.
  • 1 Hide
    Anonymous , December 1, 2008 7:31 PM

    So what I'm reading into this is users who happen to have a 2-3 year old battery and don't want to replace it will receive a performance penalty? That's utter crap!

    A laptop AC adapter must provide more than enough power to run (and here's the important part) *and* charge the battery simultaneously. This always leaves enough headroom to ensure there's enough power.

    I reject Apple's notion that a MacBook Pro without a battery will draw more power than the AC adapter it shipped with.

    In some *strange* case where a user has a 3rd party AC adapter, this might be helpful; and if a Mac user called Apple to complain about it, the first thing Apple Tech Support will say is "Do you have an Apple-supplied AC Adapter?" "No?" "We cannot support your configuration, let me direct you to sales so you can buy an apple-certified part."

    Any questions?
  • Display all 22 comments.
  • 0 Hide
    Nguy , December 1, 2008 7:57 PM
    battery discharge can be confirmed by Apple's own user guide found here:

    If on the other hand, you use a desktop computer at work, and save a notebook for infrequent travel, Apple recommends charging and discharging its battery at least once per month.
  • 0 Hide
    Anonymous , December 1, 2008 8:40 PM
    I wonder if the same holds true if the macbook is running vista/xp/Linux???? whether it is a software switch or built into the hardware?
  • 0 Hide
    Anonymous , December 1, 2008 8:52 PM
    For god sake! Who the hell believe that Apple only wants to prevent the computer from shutdown when not having the battery? It's a clear way to force deprecation on old notebooks as their batteries become inoperable faster. And I read about this "policy" one year and half ago. I just can't believe that Apple can't do a powerful enough adapter but prefers that the commercial clockwork keeps going.
  • 0 Hide
    nukemaster , December 1, 2008 11:00 PM
    So if the power adapter can not run the notebook on its own, how the hell does it change it? Does encoding a video on it have to draw into the batter eventually killing it? Something is not right.

    The macbooks should not even need that much power.
  • 0 Hide
    resonance451 , December 1, 2008 11:01 PM
    Keep in mind that li-ion batteries are not the same as the older nickel-based batteries.
  • 0 Hide
    brendano257 , December 1, 2008 11:51 PM
    I think it was a legitimate concern when building and programming the laptop, but I think the editor could have possibly made a better title, I read this because I looked at the title and though "Really does it now?"
  • -1 Hide
    lbjack , December 2, 2008 12:53 AM
    The CPU power is cut because the AC adaptor can't support it? The CPU needs both AC AND battery power to fully work? There is either super incompetence here or some kind of ridiculous battery scam going on, as suggested by another post. This is the most assinine thing I've ever heard!
  • -1 Hide
    raider37 , December 2, 2008 4:20 AM
    Yeah something is up, an adapter should be able to provide more than sufficient power to keep ure laptop going at full load AND charge ure battery at the same time, if not, then while ure using your macbook for whatever purpose, the battery would only be charged intermittently while attached to the laptop and hence significantly increasing charging times.

    I'm guessing apple decided to make a lower powered adapter in order to increase profits while cheating the consumer. Its a shame, dell, toshiba, Hp and the rest making good adpators that charge ure laptop's battery while plugged in and do it pretty darn quickly (even if ure using your pc at the time).

    They (however) do get very hot in the process so i'm guessing the components used in them are cheap as well. Either way, i'd rather have a laptop running at full power with or without the battery rather than castrated performance cause the battery was missing when i decided to use my laptop. Crazy stuff!
  • 0 Hide
    Anonymous , December 2, 2008 9:20 AM
    'i-savings' HAHAA they - like in late 90's Toshiba - used battery as buffor. If battery isn't fully charged (or its dead) some Toshiba notebooks was unable to turn on on power supply. ...savings , savings ...
  • 0 Hide
    zodiacfml , December 2, 2008 10:53 AM
    i agree with all people here. we know that an AC adapter should be more than capable of charging and operating a notebook at the same time.
    also on the part, we know that a complete discharge will destroy a lithium ion battery faster, i think its also the same with NiMH.
    the only advantage of a complete discharge is avoidance of memory effect which is not present in lithium ion batteries.

    i could have believed one comment here that it forces depreciation faster but i DON'T think an old battery will force the macbook slower.
    one thing good though with having a battery always on the notebook is avoiding loss of data during power failures.
  • -2 Hide
    aj28 , December 2, 2008 11:22 PM
    I find it really hard to believe the conspiracy theorists who think Apple is doing this to force decreased battery life upon the masses as a method of selling more replacement hardware. I mean, their logic makes sense, and frankly I'd prefer using Apple's compact 85W adapter with this type of functionality to them pushing a larger, bulkier adapter for those rare times that the entire system is running at full capacity. Adapter efficiency under extreme heat also factors in...

    The point of this article is not that Apple notebooks are constantly sucking on the battery even when plugged in. It is that occasionally when your 2.8Ghz processor, 15" screen (brightness cranked), 9600 GT, and 7200RPM HDD (the Macbook Pro's top configuration) are all running at max capacity, you may need to use a bit of the batteries power, and Apple has taken steps to ensure your system doesn't shut down. What other notebook fits that kind of capacity into an 85W envelope anyway? Most others, comparably configured, would ship with a bulky-as-hell 120W which, believe you me, is not something you want to travel with, a fact which entirely eliminates the advantage of the Macbook Pro's design.

    Yes, Apple could have designed the functionality better. Spikes in power demand are certainly hard to detect in time to prevent a shutdown, but not so hard that this functionality should be turned on all the time, regardless of load. However...

    While a lot of you may not like Apple, that shouldn't spur you to stretch every bit of negative press into a conspiracy based on ignorance.
  • 0 Hide
    WiSatman , December 3, 2008 12:07 AM
    Simulated conversation that I would have with myself if I had an Apple Macbook.

    "Hey sweet I gonna play (insert 3D game here)."

    "Oh damn I left my Macbook in standby and only have 25% battery. I guess that means I can only play (3D game) for 30 minutes or so before my battery runs out and my Macbook goes into cripple mode."

    "Guess I shouldn't have gotten that 9600 GT, or maybe that 2.8 Ghz processor, or it could be that 7200 RPM hard drive draining my battery."

    "Actually I guess I shouldn't have bought a Macbook, because it is incapable of sustained full load use and charging itself.
  • 0 Hide
    Anonymous , December 3, 2008 12:57 AM
    I can understand Apple's using the battery as buffer,however if you're running a processor intensive task (EG: Video encoding,or frame rendering) the battery will lose it's charge.

    On normal conditions this should not be an issue, since most programs only require a small cpu or GPU loadtime,and the majority of the time the processor is running at low speed,saving power which can be directed to charging the battery.

    Apple's computers aren't really made for gaming anyways, but that they advise to run a Li-ion battery totally empty I find weird.

    It is so, that a Li-ion battery can be destroyed (can never reach the voltage needed to start charging) when being completely empty.

  • 1 Hide
    kamkal , December 3, 2008 4:34 PM

    this is because apple's ac adapters are garbage.

    why do people continue to buy this overpriced junk??
  • 0 Hide
    razor512 , December 3, 2008 4:44 PM
    It is a marketing scam that apple has going on. Make the batteries die faster rather you use them or not that way users are forced to buy more batteries

    the adapter gives enough power

    my friend has a mac book pro and when running a 3d modeler, he left the PC rendering for over a week

    if the adapter didn't give enough power, then the battery would have dies within hours

  • 0 Hide
    nukemaster , December 3, 2008 9:13 PM
    It is a marketing scam that apple has going on. Make the batteries die faster rather you use them or not that way users are forced to buy more batteries

    the adapter gives enough power

    my friend has a mac book pro and when running a 3d modeler, he left the PC rendering for over a week

    if the adapter didn't give enough power, then the battery would have dies within hours

    Or it just clocked back when the battery got too low.
  • 0 Hide
    razor512 , December 4, 2008 5:32 PM
    nukemasterOr it just clocked back when the battery got too low.

    nope, he uses the laptop a lot while rendering as his college courses require him to do a lot of work

    the battery stays fully charged all the time no matter what the cpu load

    he runs maya 3d and to get better results, I thought him how to make more realistic metal by combining the DGS material (not commonly recommended especially by professors as it is nearly impossible to do animation using a single pc), with the dielectric material to allow a shiny metal look with a nice detailed gloss look

    the problem with this is that it can turn a 4 hour mental ray render task, into a 4-5 day render task
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