Using MacBook power adapter with MacBook Pro

On 05/03/08 11:26 AM, "Niall O Broin" <niallmakalumedia.com> saith :

> I came back from a trip but my MBP's power adapter didn't. I've
> connected my MBP to my son's MB power adapter and it works just
> nicely, has fully charged the battery, and is not noticeably warmer
> than it ever was. Is there something I'm missing in terms of
> potential problems?

What are the ratings on son's MB power adapter:
V in
V out
Mv
Amps

MacBook Pro adapter:
V in 110/240
V out 18.5
Mv
Amps 4.6
V out 16.5/3.6A

    Max Manshel, Esq.

On 5/3/08 at 8:26 AM, niallmakalumedia.com (Niall O Broin) wrote:

>I came back from a trip but my MBP's power adapter didn't. I've
>connected my MBP to my son's MB power adapter and it works just
>nicely, has fully charged the battery, and is not noticeably warmer
>than it ever was. Is there something I'm missing in terms of
>potential problems?

No, there should be no problems with what you are doing.

>> I came back from a trip but my MBP's power adapter didn't. I've
>> connected my MBP to my son's MB power adapter and it works just
>> nicely, has fully charged the battery, and is not noticeably warmer
>> than it ever was. Is there something I'm missing in terms of
>> potential problems?
>
> No, there should be no problems with what you are doing.

How about the other way around?

John

Sent from my iPhone (so don't blame me for spelling mistakes)

On Sat, 3 May 2008, Niall O Broin wrote:

> I came back from a trip but my MBP's power adapter didn't. I've
> connected my MBP to my son's MB power adapter and it works just
> nicely, has fully charged the battery, and is not noticeably warmer
> than it ever was. Is there something I'm missing in terms of potential
> problems?

In theory, the 60 watt charger for a Macbook isn't adequate to properly
charge & run a MBP, which comes with an 85 watt adapter.

In practice, as you say, it seems to be fine for at least short term
use, though I'm not sure if under-powering it causes long term issues.

(By way of comparison, the DC airline adapter only has 45 watts of
power. It's claimed to be enough to run the computer indefinitely, but
doesn't provide enough power to replenish the battery. Performance with
the Macbook Air charger should be similar, as it also has 45 watts. I'm
guessing you'll see something similar with long term use of the Macbook
charger with a MBP, but again, I'm not sure if long term use will put
too much stress on the adapter, the battery, or the computer itself.)


--
Chris Devers

On Sun, 4 May 2008, John Massengale wrote:

> How about the other way around?

That's fine, the 85w from the MBP to a MB (or MBA) is more power than it
needs, but shouldn't hurt anything.

Likewise, the 65w Powerbook adapter is fine for the iBook, but the
inverse with the iBook 45w adapter to charge a Powerbook works short
term, but could cause problems long term.



--
Chris Devers

On 5/4/08 at 2:39 AM, johnmassengale.com (John Massengale) wrote:

>>>I came back from a trip but my MBP's power adapter didn't. I've
>>>connected my MBP to my son's MB power adapter and it works just
>>>nicely, has fully charged the battery, and is not noticeably
>>>warmer than it ever was. Is there something I'm missing in terms
>>>of potential problems?

>>No, there should be no problems with what you are doing.

>How about the other way around?

The key to using MB charger in place of a MBP charger is the
battery voltage that should be the same for both. The
characteristic of the two chargers that will differ is the
maximum power they can supply.

Using a charger that has a lower power rating means longer times
to fully charge a battery. The way to make this most noticeable
would be to use the machine for some CPU intensive task while
attempting to charge the battery.

Using a charger with a higher power rating will not shorten the
time to charge the battery since the charging current is
determined by the circuit design of the computer. That design
determines the maximum charge current for the battery. Having a
more capable charger cannot change this.

So, there really should be no problem with using a MB charger in
place of a MBP charger or vice versa.

On 5 May 2008, at 12:55, Bill Rowe wrote:

> Using a charger that has a lower power rating means longer times
> to fully charge a battery. The way to make this most noticeable
> would be to use the machine for some CPU intensive task while
> attempting to charge the battery.
>
> Using a charger with a higher power rating will not shorten the
> time to charge the battery since the charging current is
> determined by the circuit design of the computer. That design
> determines the maximum charge current for the battery. Having a
> more capable charger cannot change this.
>
> So, there really should be no problem with using a MB charger in
> place of a MBP charger or vice versa

The curious thing here is that the MB charger's rating is 16.5V/3.65A
while
the MBP is rated at 18.5V/4.6A AND 16.5V/3.65A. The MBP's battery is
10.8V
so 16.5V should be a more than adequate charging voltage. The bottom
line is
that without more detailed information about the MB's/MBP's circuitry
than is
available it's hard to assess why they have different voltages, but
what can
be said with certainty is that in empirical testing, an MBP both runs
and charges
just nicely with an MB charger and the charger does not appear to get
excessively
hot in use.


Kindest regards,



Niall O Broin