12 volt adapter for macbook pro?

Discussion in 'Misc' started by tom koehler, Feb 22, 2011.

  1. tom koehler

    tom koehler Guest

    My wife and I have a macbook pro which we take with us in our teardrop
    trailer. The trailer has a 12 volt electrical system. Usually we use a 120V
    inverter to power the mac. I am thinking there is a lot of wasted power here,
    going from 12VDC up to 120VAC and then back down to mac voltage whatever it
    is coming out of the (magsafe) power supply.

    I know the magsafe plug is patented and not licensed to any non-Apple
    manufacturers. I also believe that the only cable that mac makes is an
    airline adapter - said to be able to run the mac but not recharge the
    battery. About $50. Why won't this cable work for recharging the battery? Is
    the airplane voltage too low for battery charging but maybe high enough for
    just running the computer?

    Okay, I'm steamed about a lot of little things in life and maybe this is one
    of them. I can deal with this cable being a bit overpriced, but then it does
    not seem to have an automotive-type plug on it. Rather, the plug is for
    airline application and a different plug. I can deal with that. A wire cutter
    and a few minutes soldering to an automotive style 12 volt plug, and I'm
    goodŠ But - there's the issue of voltage. What diet is the mac on? I can dope
    out the polarity, and I could very likely measure the output voltage of the
    macbook's power supply. If I really wanted to, I have no doubt that I could
    manufacture my own darned magsafe plug, too.

    First, try the usenet folks and see if others have dealt with this. Maybe I
    don't have to reinvent the wheel.

    Has anyone else dealt with running their macbook pro on 12 volts - without
    also using a 120 volt ac inverter first?

    tom koehler
    --
    I will find a way or make one.
    tom koehler, Feb 22, 2011
    #1
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  2. tom koehler

    nospam Guest

    In article <>, tom
    koehler <> wrote:

    > My wife and I have a macbook pro which we take with us in our teardrop
    > trailer. The trailer has a 12 volt electrical system. Usually we use a 120V
    > inverter to power the mac. I am thinking there is a lot of wasted power here,
    > going from 12VDC up to 120VAC and then back down to mac voltage whatever it
    > is coming out of the (magsafe) power supply.


    it's a waste to convert twice.

    the macbook pro adapter is 85 watts, and you'll only get about 60-70
    watts continuous from a typical inverter that plugs into the cigarette
    lighter. if you want more power, you'll need one that is hardwired to
    the battery. plus, inverters generally give the peak output (not
    continuous) because the number is bigger, so read the fine print.

    you can also use a macbook 60w adapter to run the macbook pro to keep
    under the limit of the inverter. it will just charge slower (and if the
    macbook's battery is fully charged, you won't notice any difference).

    > I know the magsafe plug is patented and not licensed to any non-Apple
    > manufacturers.


    yep, which is incredibly annoying, especially for people who fly.

    > I also believe that the only cable that mac makes is an
    > airline adapter - said to be able to run the mac but not recharge the
    > battery. About $50. Why won't this cable work for recharging the battery? Is
    > the airplane voltage too low for battery charging but maybe high enough for
    > just running the computer?


    it's because it was designed by someone who doesn't fly and has no
    interest in providing a product that is useful to those to do. it's
    junk.

    it doesn't even provide enough current to run a macbook pro (it might
    be ok for a macbook air though). the battery will slowly discharge,
    just not as fast as if it was on battery only.

    > Okay, I'm steamed about a lot of little things in life and maybe this is one
    > of them.


    if you haven't noticed, i'm steamed about it too. i fly a lot and
    apple's magsafe adapter is worthless and a complete waste of money.

    > I can deal with this cable being a bit overpriced, but then it does
    > not seem to have an automotive-type plug on it.


    yes it does.

    the magsafe airline adapter comes with an empower plug and a slide-on
    cigarette lighter adapter because airline seat power uses both types of
    plugs. despite that, it does not work in a car.

    there is also no locking mechanism for the cigarette adapter piece
    (other than friction and it's polished plastic, so not much) which
    means it slides off way too easy. if you fly a lot, you might find one
    stuck in the seat power outlet from a previous passenger. i've found a
    couple.

    > Rather, the plug is for
    > airline application and a different plug. I can deal with that. A wire cutter
    > and a few minutes soldering to an automotive style 12 volt plug, and I'm
    > goodŠ


    no need. see above. plus, you can buy empower-cigarette adapters
    anyway, for either direction.

    > But - there's the issue of voltage. What diet is the mac on? I can dope
    > out the polarity, and I could very likely measure the output voltage of the
    > macbook's power supply. If I really wanted to, I have no doubt that I could
    > manufacture my own darned magsafe plug, too.


    it's more difficult than you think because there's an id chip in the
    magsafe plug itself that identifies the adapter to the computer.

    anyway, the macbook runs on 24v and airline seat power provides 15v.
    the adapter is basically a straight wire (no step-up) and it tells the
    computer to disable charging.

    > First, try the usenet folks and see if others have dealt with this. Maybe I
    > don't have to reinvent the wheel.


    you don't have to reinvent anything.

    > Has anyone else dealt with running their macbook pro on 12 volts - without
    > also using a 120 volt ac inverter first?


    get one of the chinese magsafe auto/air adapters on ebay. they're 20-30
    bucks or so, and unlike apple's p.o.s., it actually charges the
    computer, it works on a plane and in a car, as well as any 12v supply.
    i have one and it works *very* well. i should have bought it long ago.

    newer planes now have 110vac plugs so you can use the standard ac
    adapter and not deal with any of this. the only problem is there are
    still a lot of planes that use the older dc seat power, so you still
    need to carry an airline/auto adapter too.
    nospam, Feb 22, 2011
    #2
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  3. tom koehler

    Jolly Roger Guest

    nospam <> wrote:
    > In article <>, tom
    > koehler <> wrote:
    >
    >> My wife and I have a macbook pro which we take with us in our teardrop
    >> trailer. The trailer has a 12 volt electrical system. Usually we use a 120V
    >> inverter to power the mac. I am thinking there is a lot of wasted power here,
    >> going from 12VDC up to 120VAC and then back down to mac voltage whatever it
    >> is coming out of the (magsafe) power supply.

    >
    > it's a waste to convert twice.


    Wasteful or not, with a DC - AC converter we can use the MacBook Pro (andr
    lots of other AC devices) on the road for hours on end without issue.
    Nothing you can say changes the fact that it works very well.

    --
    Posted from my iPhone.
    Jolly Roger, Feb 22, 2011
    #3
  4. tom koehler

    nospam Guest

    In article
    <>,
    Jolly Roger <> wrote:

    > >> My wife and I have a macbook pro which we take with us in our teardrop
    > >> trailer. The trailer has a 12 volt electrical system. Usually we use a
    > >> 120V inverter to power the mac. I am thinking there is a lot of wasted power
    > >> here, going from 12VDC up to 120VAC and then back down to mac voltage whatever
    > >> it is coming out of the (magsafe) power supply.

    > >
    > > it's a waste to convert twice.

    >
    > Wasteful or not, with a DC - AC converter we can use the MacBook Pro (andr
    > lots of other AC devices) on the road for hours on end without issue.
    > Nothing you can say changes the fact that it works very well.


    suit yourself, but the fact remains that a dc-ac-dc conversion is a
    waste. you can't avoid physics.

    i fussed with inverters on planes for a few months. what a pain in the
    ass that was.

    what tom needs is one of the chinese magsafe auto/air adapters.
    nospam, Feb 22, 2011
    #4
  5. In article
    <>,
    Jolly Roger <> wrote:

    > nospam <> wrote:
    > > In article <>, tom
    > > koehler <> wrote:
    > >
    > >> My wife and I have a macbook pro which we take with us in our teardrop
    > >> trailer. The trailer has a 12 volt electrical system. Usually we use a
    > >> 120V
    > >> inverter to power the mac. I am thinking there is a lot of wasted power
    > >> here,
    > >> going from 12VDC up to 120VAC and then back down to mac voltage whatever
    > >> it
    > >> is coming out of the (magsafe) power supply.

    > >
    > > it's a waste to convert twice.

    >
    > Wasteful or not, with a DC - AC converter we can use the MacBook Pro (andr
    > lots of other AC devices) on the road for hours on end without issue.
    > Nothing you can say changes the fact that it works very well.


    You ignored the OP's point that he does that now, but wants a more
    energy-efficient system:

    > My wife and I have a macbook pro which we take with us in our teardrop
    > trailer. The trailer has a 12 volt electrical system. Usually we use a 120V
    > inverter to power the mac. I am thinking there is a lot of wasted power here,
    > going from 12VDC up to 120VAC and then back down to mac voltage whatever it
    > is coming out of the (magsafe) power supply.



    Tom/OP: Google is your friend. I found the following by Googling
    "airline adapter voltage". There seem to be two solutions here, one that
    allows charging and one that does not.

    <http://pangea.stanford.edu/~schmitt/magsafe/>

    I suspect that this <http://mikegyver.com/> is the for-fee site that
    Stuart Schmitt mentions. Or, it's the site he suggests as the place to
    buy the pre-assembled version.

    YMMV. No warranty expressed or implied. All offers made only by the
    prospectus. Dog ate my homework.

    Steve

    --
    steve <at> w0x0f <dot> com
    "Life should not be a journey to the grave with the intention of
    arriving safely in an attractive and well preserved body, but rather to
    skid in sideways, chocolate in one hand, sidecar in the other, body thoroughly
    used up, totally worn out and screaming "WOO HOO what a ride!"
    Steve Fenwick, Feb 22, 2011
    #5
  6. tom koehler

    tom koehler Guest

    On Tue, 22 Feb 2011 1:00:47 -0600, nospam wrote
    (in message <220220110200476642%>):


    >
    >> I can deal with this cable being a bit overpriced, but then it does
    >> not seem to have an automotive-type plug on it.

    >
    > yes it does.
    >
    > the magsafe airline adapter comes with an empower plug and a slide-on
    > cigarette lighter adapter because airline seat power uses both types of
    > plugs. despite that, it does not work in a car.


    aha - okay that is a start
    >
    > there is also no locking mechanism for the cigarette adapter piece
    > (other than friction and it's polished plastic, so not much) which
    > means it slides off way too easy.


    I could easily deal with that

    if you fly a lot,

    I'm not a flyer. would prefer a self administered root canal with a beer can
    opener

    >
    >


    >
    > it's more difficult than you think because there's an id chip in the
    > magsafe plug itself that identifies the adapter to the computer.


    arrgh!
    >
    >


    >
    > get one of the chinese magsafe auto/air adapters on ebay. they're 20-30
    > bucks or so, and unlike apple's p.o.s., it actually charges the
    > computer, it works on a plane and in a car, as well as any 12v supply.
    > i have one and it works *very* well. i should have bought it long ago.


    I will investigate this. thanks
    >
    >


    tom koehler

    --
    I will find a way or make one.
    tom koehler, Feb 22, 2011
    #6
  7. tom koehler

    tom koehler Guest

    On Tue, 22 Feb 2011 1:55:41 -0600, Steve Fenwick wrote
    (in message <>):

    >
    > Tom/OP: Google is your friend. I found the following by Googling
    > "airline adapter voltage". There seem to be two solutions here, one that
    > allows charging and one that does not.
    >
    > <http://pangea.stanford.edu/~schmitt/magsafe/>
    >
    > I suspect that this <http://mikegyver.com/> is the for-fee site that
    > Stuart Schmitt mentions. Or, it's the site he suggests as the place to
    > buy the pre-assembled version.
    >
    > YMMV. No warranty expressed or implied. All offers made only by the
    > prospectus. Dog ate my homework.
    >
    > Steve
    >


    thanks for the info. I have tried google but got bogged down in dozens fo
    variations on the same 2 themes, neither of which involved the stanford link.
    I just gave that link a brief look and much of it is either promising or
    educational - re Apple's efforts to protect its proprietary turf. Will now go
    study more closely. Am encouraged.
    tom koehler



    --
    I will find a way or make one.
    tom koehler, Feb 22, 2011
    #7
  8. tom koehler

    David Lesher Guest

    There are multiple issues:

    A) The aircraft jack will only furnish 75 watts. Laptop power consumption
    exceeds that in many cases.

    B) In some aircraft, they can't manage even that; and a circuit
    breaker trips; taking out a row of seats.

    C) You'd think a smart company like Apple could design an
    adapter that always drew less than that, but...

    D) Charging NiMH and Li batteris is far less straight forward
    than older NiCad's and lead-acid ones.

    E) There's lots of concern on charging batteries mid-flight given how
    sometimes they catch fire...


    --
    A host is a host from coast to
    & no one will talk to a host that's close........[v].(301) 56-LINUX
    Unless the host (that isn't close).........................pob 1433
    is busy, hung or dead....................................20915-1433
    David Lesher, Feb 22, 2011
    #8
  9. tom koehler

    tom koehler Guest

    On Tue, 22 Feb 2011 10:51:06 -0600, tom koehler wrote
    (in message <>):

    > On Tue, 22 Feb 2011 1:55:41 -0600, Steve Fenwick wrote
    > (in message <>):
    >
    >>
    >> Tom/OP: Google is your friend. I found the following by Googling
    >> "airline adapter voltage". There seem to be two solutions here, one that
    >> allows charging and one that does not.
    >>
    >> <http://pangea.stanford.edu/~schmitt/magsafe/>
    >>
    >> I suspect that this <http://mikegyver.com/> is the for-fee site that
    >> Stuart Schmitt mentions. Or, it's the site he suggests as the place to
    >> buy the pre-assembled version.
    >>
    >> YMMV. No warranty expressed or implied. All offers made only by the
    >> prospectus. Dog ate my homework.
    >>
    >> Steve
    >>

    >
    > thanks for the info. I have tried google but got bogged down in dozens fo
    > variations on the same 2 themes, neither of which involved the stanford
    > link.
    > I just gave that link a brief look and much of it is either promising or
    > educational - re Apple's efforts to protect its proprietary turf. Will now
    > go
    > study more closely. Am encouraged.
    > tom koehler
    >
    >
    >
    >


    I did some more google-ing (googleage?) and came up with this:
    http://www.amazon.com/Charger-Laptop-Adapter-Power-
    Apple/dp/B002U242WI/ref=pd_rhf_p_t_1

    I ordered one and we shall see what we sahll see. No doubt made in China...
    almost everything sold in the US is. It promises me that it will run and
    charge and is rated at 85 watts. Price was around $30 and another few for
    delivery.

    Oddly enough, when I set out to do some more searching - on one of my
    searches the first thing that popped up was the entire thread here on this
    usenet board, item by item, and the electrons hadn't even cooled off yet,
    from my last psoting here. It was on some mac-specific discussion forum. heh.
    Gotta love them harvester ants, or spiders, or whatever it is that "they"
    use.
    Will keep you posted on initial results of this unit, when I get it.
    tom koehler

    --
    I will find a way or make one.
    tom koehler, Feb 22, 2011
    #9
  10. tom koehler

    nospam Guest

    In article <ik12ei$okl$>, David Lesher
    <> wrote:

    > There are multiple issues:
    >
    > A) The aircraft jack will only furnish 75 watts. Laptop power consumption
    > exceeds that in many cases.


    however, a macbook pro can run on a 60w macbook adapter (and probably a
    40w macbook air adapter but i don't have one to try).

    > B) In some aircraft, they can't manage even that; and a circuit
    > breaker trips; taking out a row of seats.


    nope, it only takes out the single port. i've popped it a couple of
    times when i was messing with inverters (because the magsafe airline
    adapter is garbage). i have a 75w inverter and plugged in a 60w adapter
    and it pops every once in a while. it comes right back.

    > C) You'd think a smart company like Apple could design an
    > adapter that always drew less than that, but...


    the magsafe airline adapter draws around 30-40 watts, well within the
    limit for an airline, and it is insufficient to *run* a macbook pro.
    you would think they could make an adapter that worked with their own
    products.

    > D) Charging NiMH and Li batteris is far less straight forward
    > than older NiCad's and lead-acid ones.


    apple hasn't used nimh for about 10 years and nimh is not that
    difficult (it's similar to nicad).

    > E) There's lots of concern on charging batteries mid-flight given how
    > sometimes they catch fire...


    the only concern is from idiots who don't fly.

    if the battery is going to catch fire, it's better if it happens while
    the user is sitting in front of it (or their seatmate if the user took
    a bathroom break), ready to extinguish any fire. they will probably
    notice the smoke *before* it catches fire. plus, there are fire
    extinguishers on board, along with a trained flight crew who can put
    out any fire. the risk is nowhere near what some might want you to
    believe.

    it might cause a flight diversion due to smoke, but a small fire won't
    compromise the aircraft. plus, only apple products are not charging.
    all the *other* products *are* charging.

    it would be a *lot* worse if the battery caught fire on the ground
    while someone was sleeping in another room, only to wake up to the
    entire house being on fire. or maybe they went out to dinner and came
    home to a house fire. and how many people have a fire extinguisher
    ready to use? not many.
    nospam, Feb 22, 2011
    #10
  11. tom koehler

    Bruce Gordon Guest

    In article <>,
    tom koehler <> wrote:

    > My wife and I have a macbook pro which we take with us in our teardrop
    > trailer. The trailer has a 12 volt electrical system. Usually we use a 120V
    > inverter to power the mac. I am thinking there is a lot of wasted power here,
    > going from 12VDC up to 120VAC and then back down to mac voltage whatever it
    > is coming out of the (magsafe) power supply.
    >
    > I know the magsafe plug is patented and not licensed to any non-Apple
    > manufacturers. I also believe that the only cable that mac makes is an
    > airline adapter - said to be able to run the mac but not recharge the
    > battery. About $50. Why won't this cable work for recharging the battery? Is
    > the airplane voltage too low for battery charging but maybe high enough for
    > just running the computer?
    >
    > Okay, I'm steamed about a lot of little things in life and maybe this is one
    > of them. I can deal with this cable being a bit overpriced, but then it does
    > not seem to have an automotive-type plug on it. Rather, the plug is for
    > airline application and a different plug. I can deal with that. A wire cutter
    > and a few minutes soldering to an automotive style 12 volt plug, and I'm
    > goodŠ But - there's the issue of voltage. What diet is the mac on? I can dope
    > out the polarity, and I could very likely measure the output voltage of the
    > macbook's power supply. If I really wanted to, I have no doubt that I could
    > manufacture my own darned magsafe plug, too.
    >
    > First, try the usenet folks and see if others have dealt with this. Maybe I
    > don't have to reinvent the wheel.
    >
    > Has anyone else dealt with running their macbook pro on 12 volts - without
    > also using a 120 volt ac inverter first?
    >
    > tom koehler


    What I did was build my own out of a Targus AC/DC 90 Watt Switching
    Power Supply that I purchased at a computer store, years ago. This has
    two input Power cords One is 120Vac and One is 12Vdc. then you have a
    single DC Output Cord, that has various interchangeable Tips that fit
    most every bodies Laptop, Notebood, Cellphoone, Palmtop, or portable
    whatever. Each tip has a Sensing Resistor that sets the output DC voltage
    to whatever the unit, the tip is for, requires. I took the tip for my
    WallStreet G3 and measured its resistor, and then cut the MagSafe
    connector off a DEAD Apple 85 Watt AC Adapter, and built my own Output
    Power Cord Tip. Been using it for about three years now, with NO ISSUES.
    Battery charging and operating my Black MacBook.... Works for "Me"....

    --
    Bruce in Alaska add path before the @ for email
    Bruce Gordon, Feb 22, 2011
    #11
  12. tom koehler

    David Lesher Guest

    nospam <> writes:


    >> B) In some aircraft, they can't manage even that; and a circuit
    >> breaker trips; taking out a row of seats.


    >nope, it only takes out the single port. i've popped it a couple of
    >times when i was messing with inverters (because the magsafe airline
    >adapter is garbage). i have a 75w inverter and plugged in a 60w adapter
    >and it pops every once in a while. it comes right back.


    You have flown on every model of aircraft made; and tested the breakers
    on them all? Wow.

    >> E) There's lots of concern on charging batteries mid-flight given how
    >> sometimes they catch fire...


    >the only concern is from idiots who don't fly.


    I fly; and I'm concerned. There's a lot of stored energy and
    NO inflight fire is trivial. You have a limited extinguishing
    capacity; and the aircraft is built of two things; aluminum and
    processed crude oil....

    And assuming diverting is possible, much less fast & easy, is
    reckless & naive. Even if we assume all aircraft are twins on
    ETOPS routes; that's up to one hundred and twenty minutes. Not
    to worry, you'd be dead long before then. Ask the folks on Air
    Canada Flight 797; those who survived.

    That said; I'm not sure there's been a correlation proven
    between fires and *charging* laptop batteries. We'll be learning
    lots about battery fires with the coming electric cars.

    --
    A host is a host from coast to
    & no one will talk to a host that's close........[v].(301) 56-LINUX
    Unless the host (that isn't close).........................pob 1433
    is busy, hung or dead....................................20915-1433
    David Lesher, Feb 22, 2011
    #12
  13. tom koehler

    nospam Guest

    In article <ik1a7m$jr0$>, David Lesher
    <> wrote:

    > >> B) In some aircraft, they can't manage even that; and a circuit
    > >> breaker trips; taking out a row of seats.

    >
    > >nope, it only takes out the single port. i've popped it a couple of
    > >times when i was messing with inverters (because the magsafe airline
    > >adapter is garbage). i have a 75w inverter and plugged in a 60w adapter
    > >and it pops every once in a while. it comes right back.

    >
    > You have flown on every model of aircraft made; and tested the breakers
    > on them all? Wow.


    did i say that? i've flown on 6 types of boeing aircraft with seat
    power, two of which have had it disabled due to a supposed wiring issue
    (757 & 767).

    each outlet is independent and can source 75 watts and every time its
    popped, the other outlet was fully operational. one thing i have
    noticed is that the planes with 110vac outlets like to pop more easily.
    apparently the initial surge from plugging in a new device can trigger
    it, even if it's under 75 watts (which mine all are). i once had it
    reset when plugging in an iphone charger, which is about a tenth of the
    limit, yet it still cycled.

    > >> E) There's lots of concern on charging batteries mid-flight given how
    > >> sometimes they catch fire...

    >
    > >the only concern is from idiots who don't fly.

    >
    > I fly; and I'm concerned.


    i'm *far* more concerned about an airline mechanic who makes a mistake
    that isn't caught or some part fails prematurely or is installed wrong.
    there have been a number of crashes due to that.

    i'm also more concerned about pilot/atc error and even weather issues.
    there was a recent near-collision (a month or two ago, if i'm not
    mistaken) where two planes were within 200 feet of each other. that's
    *way* too close.

    meanwhile, i've yet to hear about a laptop battery fire at all, let
    alone one that caused a diversion.

    > There's a lot of stored energy and
    > NO inflight fire is trivial.


    they used to allow smoking and even provided cigarette lighters in
    every seat, so there is obviously a level at which fire (and smoke) is
    considered trivial.

    > You have a limited extinguishing
    > capacity; and the aircraft is built of two things; aluminum and
    > processed crude oil....


    there's much more to a plane than that, but regardless, planes aren't
    as fragile as you think and pilots and flight attendants are well
    trained to handle all sorts of emergencies.

    probably the best example is aloha airlines 243, the flight in which a
    portion of the roof tore off. it landed safely. the only death was a
    flight attendant who was standing in the area where the roof came off.

    > And assuming diverting is possible, much less fast & easy, is
    > reckless & naive.


    it's not reckless or naive. flights divert for a lot of reasons. i've
    been on two diversions (within a month of each other, no less). one was
    mechanical, we landed, got on another plane and took off again. the
    other was weather related and once that cleared, we continued on. it
    happens, and it's normally not that big of a deal.

    > Even if we assume all aircraft are twins on
    > ETOPS routes; that's up to one hundred and twenty minutes. Not
    > to worry, you'd be dead long before then. Ask the folks on Air
    > Canada Flight 797; those who survived.


    that was nearly 30 year ago, and because of that, airplanes are far
    more resistant to fires.

    > That said; I'm not sure there's been a correlation proven
    > between fires and *charging* laptop batteries. We'll be learning
    > lots about battery fires with the coming electric cars.


    it's extremely rare. i am unaware of *any* fire in the cabin due to
    charging a battery.

    the lithium battery fires so far include a ups jet in philadelphia a
    few years ago, but that was with batteries in the cargo hold and not
    even in use, let alone plugged into anything. another was in los
    angeles, again, in the cargo hold.

    if there really was a risk of battery fire, they'd be banned and seat
    power outlets removed on all flights everywhere. same with cellphones
    and leaving them powered up. that hasn't happened, so obviously the
    risk is not particularly high.
    nospam, Feb 23, 2011
    #13
  14. tom koehler

    nospam Guest

    In article <>, tom
    koehler <> wrote:

    > Will keep you posted on initial results of this unit, when I get it.


    please do. that's not the one i have, but it's always good to know how
    well other units work.
    nospam, Feb 23, 2011
    #14
  15. tom koehler

    Clark Martin Guest

    In article <220220110200476642%>,
    nospam <> wrote:

    > In article <>, tom
    > koehler <> wrote:
    >
    > > My wife and I have a macbook pro which we take with us in our teardrop
    > > trailer. The trailer has a 12 volt electrical system. Usually we use a 120V
    > > inverter to power the mac. I am thinking there is a lot of wasted power
    > > here,
    > > going from 12VDC up to 120VAC and then back down to mac voltage whatever it
    > > is coming out of the (magsafe) power supply.

    >
    > it's a waste to convert twice.


    Yes it is one inverter I have draws .5 A @ 12V (6W) on idle. That's a
    fair amount of power. The 12V laptop adapters i've tested draw very
    little when plugged in and the laptop is fully charged and sleeping.
    This is nice as I can leave it connected and not worry about running
    down the battery.

    >
    > the macbook pro adapter is 85 watts, and you'll only get about 60-70
    > watts continuous from a typical inverter that plugs into the cigarette
    > lighter. if you want more power, you'll need one that is hardwired to
    > the battery. plus, inverters generally give the peak output (not
    > continuous) because the number is bigger, so read the fine print.


    You can easily pull 200W from a car cigarette lighter outlet, you just
    need a larger inverter.

    >
    > you can also use a macbook 60w adapter to run the macbook pro to keep
    > under the limit of the inverter. it will just charge slower (and if the
    > macbook's battery is fully charged, you won't notice any difference).
    >
    > > I know the magsafe plug is patented and not licensed to any non-Apple
    > > manufacturers.

    >
    > yep, which is incredibly annoying, especially for people who fly.
    >
    > > I also believe that the only cable that mac makes is an
    > > airline adapter - said to be able to run the mac but not recharge the
    > > battery. About $50. Why won't this cable work for recharging the battery?
    > > Is
    > > the airplane voltage too low for battery charging but maybe high enough for
    > > just running the computer?

    >
    > it's because it was designed by someone who doesn't fly and has no
    > interest in providing a product that is useful to those to do. it's
    > junk.


    I believe it was designed to not charge the battery due to the
    unwarranted) panic over exploding LiON batteries.


    >
    > the magsafe airline adapter comes with an empower plug and a slide-on
    > cigarette lighter adapter because airline seat power uses both types of
    > plugs. despite that, it does not work in a car.


    The voltage is too low. The airline adapter works with about 20V which
    is well above what a car puts out.

    >
    > > But - there's the issue of voltage. What diet is the mac on? I can dope
    > > out the polarity, and I could very likely measure the output voltage of the
    > > macbook's power supply. If I really wanted to, I have no doubt that I could
    > > manufacture my own darned magsafe plug, too.


    You don't need to measure it, it's printed on the case, 24VDC

    >
    > it's more difficult than you think because there's an id chip in the
    > magsafe plug itself that identifies the adapter to the computer.
    >
    > anyway, the macbook runs on 24v and airline seat power provides 15v.
    > the adapter is basically a straight wire (no step-up) and it tells the
    >


    > get one of the chinese magsafe auto/air adapters on ebay. they're 20-30
    > bucks or so, and unlike apple's p.o.s., it actually charges the
    > computer, it works on a plane and in a car, as well as any 12v supply.
    > i have one and it works *very* well. i should have bought it long ago.
    >



    That's what I did. I've used mine a lot plugged into a battery pack I
    built and haul out to the field to use. It uses solar panels to charge
    it (or an AC adapter).

    --
    Clark Martin
    Redwood City, CA, USA Macintosh / Internet Consulting

    "I'm a designated driver on the Information Super Highway"
    Clark Martin, Feb 24, 2011
    #15
  16. Clark Martin wrote:

    > I believe it was designed to not charge the battery due to the
    > unwarranted) panic over exploding LiON batteries.


    It took years for Apple to recover from the burning Wallstreet (2nd generation
    G3 laptops) and other brands, e.g. Dell suffered from the same problem.

    While many (as in more than a few) laptops caught fire, AFAIK none were
    on airplanes at the time.

    About once a year there is an exploding battery story in the press, which
    keeps it in people's minds. AFAIK it has not happened on an Apple laptop since
    the release of the Wallstreet PDQ (the replacment for the original one).

    The cost of the battery fires was very high for Apple. They paid for a big
    product placement deal with the producers of the movie "Independence Day".

    Jeff Goldblum used a Wallstreet to save the world, and there were many shots
    of him holding the laptop and the Apple logo.

    Because of the fires, those shots were edited out of the released movie,
    and unless you know what to look for you won't see it at all.

    Geoff.


    --
    Geoffrey S. Mendelson N3OWJ/4X1GM
    Those who cannot remember the past are condemned to misquote it.
    Geoffrey S. Mendelson, Feb 24, 2011
    #16
  17. tom koehler

    nospam Guest

    In article
    <>,
    Clark Martin <> wrote:

    > > the macbook pro adapter is 85 watts, and you'll only get about 60-70
    > > watts continuous from a typical inverter that plugs into the cigarette
    > > lighter. if you want more power, you'll need one that is hardwired to
    > > the battery. plus, inverters generally give the peak output (not
    > > continuous) because the number is bigger, so read the fine print.

    >
    > You can easily pull 200W from a car cigarette lighter outlet, you just
    > need a larger inverter.


    200 watts would be just under 15 amps (ignoring any losses in the
    inverter). good luck on not blowing a fuse. a car's cigarette lighter
    is *not* designed for that.

    here's a typical car inverter. it's 90w peak, 75w continuous.
    <http://us.kensington.com/html/13884.html>

    > > the magsafe airline adapter comes with an empower plug and a slide-on
    > > cigarette lighter adapter because airline seat power uses both types of
    > > plugs. despite that, it does not work in a car.

    >
    > The voltage is too low. The airline adapter works with about 20V which
    > is well above what a car puts out.


    airline seat power is 15v and a car is 13.8v (while running). that's
    not a huge difference. had it been designed properly, it would have
    worked with both.
    nospam, Feb 24, 2011
    #17
  18. tom koehler

    tom koehler Guest

    Re: 12 volt adapter for macbook pro? Redux

    I got the cable. It is 1
    "Car Charger Dc Laptop Adapter Power Cord for Apple Mac"
    $29.90

      Sold by: PWR+

    with shipping, it came to about $36. Works like a charm. Run the computer.
    Idle the computer. Charge the computer. Lights turn orange or green,
    according to the state of the charge. Just like it was done the regular way.
    Made in China.
    I'm happy. Momma is happy.
    tom koehler

    --
    I will find a way or make one.
    tom koehler, Feb 27, 2011
    #18
  19. tom koehler

    David Lesher Guest

    Re: 12 volt adapter for macbook pro? Redux

    tom koehler <> writes:

    >I got the cable. It is 1
    >"Car Charger Dc Laptop Adapter Power Cord for Apple Mac"
    >$29.90


    >  Sold by: PWR+


    >with shipping, it came to about $36. Works like a charm. Run the computer.
    >Idle the computer. Charge the computer. Lights turn orange or green,
    >according to the state of the charge. Just like it was done the regular way.
    >Made in China.
    >I'm happy. Momma is happy.
    >tom koehler


    Comment seen:

    "The charger only maintains the current charge of the of the
    laptop battery. My MacBook Pro correctly indicates the charger
    does not charge the battery."
    --
    A host is a host from coast to
    & no one will talk to a host that's close........[v].(301) 56-LINUX
    Unless the host (that isn't close).........................pob 1433
    is busy, hung or dead....................................20915-1433
    David Lesher, Feb 28, 2011
    #19
  20. tom koehler

    tom koehler Guest

    Re: 12 volt adapter for macbook pro? Redux

    On Mon, 28 Feb 2011 13:39:09 -0600, David Lesher wrote
    (in message <ikgtkt$egs$>):

    > tom koehler <> writes:
    >
    >> I got the cable. It is 1
    >> "Car Charger Dc Laptop Adapter Power Cord for Apple Mac"
    >> $29.90

    >
    >>   Sold by: PWR+

    >
    >> with shipping, it came to about $36. Works like a charm. Run the computer.
    >> Idle the computer. Charge the computer. Lights turn orange or green,
    >> according to the state of the charge. Just like it was done the regular
    >> way.
    >> Made in China.
    >> I'm happy. Momma is happy.
    >> tom koehler

    >
    > Comment seen:
    >
    > "The charger only maintains the current charge of the of the
    > laptop battery. My MacBook Pro correctly indicates the charger
    > does not charge the battery."
    >


    My communications skills may not be as good as they should be. Your remarks
    are a minor puzzle to me, as I am not sure if they are intended to relate to
    mine.
    The charger unit I got works for me. It successfully charged the computer.
    When the computer indicated full charge, the indicator light on the charger
    unit also turned green, indicating completion of charge.
    I am not trying to refute or disagree with anything you have posted. I am
    only relating and reiterating my experience with my own situation.
    Respectfully,
    tom koehler


    --
    I will find a way or make one.
    tom koehler, Mar 1, 2011
    #20
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