Using another macbook pro charger might damage my macbook pro battery??

E999 wrote:

So just to let him be at ease, we both have macbook pros, if i use his charger and then he uses it back it WILL NOT affect negatively his battery in ANY way.. Right??

Come on please! Its just an AC power adapter. It supplies whatever voltage and wattage, up to its max output, of what is connect to it. It has no memory, does not record what unit it was connect to last and or now, will not do anything other then supply power to what is connect to it.

Kappy wrote:

Don't bet your charger on that. It's quite possible to exceed the over-current protection of a power supply (assuming it has one) and cause heat damage or part failure. There are limits in which you can drain 85 watts of power from a device designed to supply only 60 watts.

Having designed, built, and used power supplies over my last 50 years I think I understand a little about their limitations.

Perfectly designed power supplies contain both over-voltage and over-current protection, but it's more important to provide over-voltage protection for computers than it is over-current, so the latte is often if not always omitted.

Both over voltage and over current protection are mandatory, unless you want to go without UL listing, and Apple for one has UL listed supplies. While you are correct in a broad sense the issue is not an issue with properly compliant power supplies.

Having spent some years designing large RF & AF power supplies (50hz to 400hz for the big power amplifiers) I too know my way around them.

As for over voltage rather than over current protection note that all that is required to prevent over current (assuming a fixed load) is to limit the voltage across the load, it's 2 halves of the same thing.

Go with your gut, or listen to the cricket, if it sounds illogical, then it probably is. Your friend is paranoid, but you already knew that.

MacBooks and MacBook Pro are regulated, that is why you can use them all over the world. Europe even uses higher voltage sockets 210V.

even if the charger was a 65w instead of an 85w, at most it would work, at least, it would keep your MBP powered but not charge the battery. 40-60w may not even sustain the power for use...

Kappy wrote:

Don't bet your charger on that. It's quite possible to exceed the over-current protection of a power supply (assuming it has one) and cause heat damage or part failure. There are limits in which you can drain 85 watts of power from a device designed to supply only 60 watts.

Having designed, built, and used power supplies over my last 50 years I think I understand a little about their limitations.

Perfectly designed power supplies contain both over-voltage and over-current protection, but it's more important to provide over-voltage protection for computers than it is over-current, so the latte is often if not always omitted.

Sorry but a 60 watt charger will not supply 85 or 90 watts. It will supply 60 all day long. that is why it is rated at 60 watts. If it does TRY to supply a wattage above its stated wattage then there is something wrong with the charger.

Read carefully. You are thinking about battery charging alone. However, the charger and the battery may both be required to provide the power demanded under extreme CPU/GPU usage. Neither alone is able to supply the power demands at the extreme. Hence the reason why when on battery power only the CPU throttles to a lower speed in order to prevent excessive power demands from the battery alone.

My remarks have to do with what's going on inside the adaptor, and that is why Apple specifically recommends you do not use a lower-rated charger than required by your computer.

Insofar as the load resistance isn't changing nor is the voltage changing, then the only variable is current. Because wattage is the product of current times voltage as more power is used by definition more current is drained. Thus, without proper protection it's possible to exceed the currrent ratings of components making up the system in question. This results in heating and potential component damage. BTW, this is all in cooperation with Ohm's law.

E999 wrote:

So just to let him be at ease, we both have macbook pros, if i use his charger and then he uses it back it WILL NOT affect negatively his battery in ANY way.. Right??

correct

Kappy wrote:

Read carefully. You are thinking about battery charging alone. However, the charger and the battery may both be required to provide the power demanded under extreme CPU/GPU usage. Neither alone is able to supply the power demands at the extreme. Hence the reason why when on battery power only the CPU throttles to a lower speed in order to prevent excessive power demands from the battery alone.

That is because battery charging is the ONLY factor, the Mac does not run directly from the charger (unless no battery is present, or no functional battery is present) current is drawn from the battery as needed, the supply recharges the battery at a constant rate. If you are curious get an AC current clamp, pop the AC cord open and separate the positive line, pop the clamp around it and monitor current draw, there are 2 states, on, or off.

If the rate of charge is lower than the average consumption the battery will go flat, if not the battery will charge (or remain in equilibrium)

No that is not why they, Apple, recommends (and right there they do not say DON'T USE. They Recommend) not using a lower wattage adapter. It is because if you do you will only be able to either use the notebook or charge the battery but not both at the same time.

God forbid for a Mac user to have his/her MBP plugged in for 5 hours and using it for that whole time only to find out that when he unplugged it the battery was as low on charge as it was when he/she first plugged it in.

Just think of the calls to Apple Care.

Hi guys,

i have been using a non-apple charger for my late 2008 13" MacBook for about 4 years. It was the correct wattage for my model (60w MagSafe 1), but sadly conked out about a month ago.

since then I have been using a macbook pro MagSafe 1 charger that i believed was the same but the just realised the output is 18.5V whereas my previous charger was 16.5v.

The macbook pro charger has had its own issues. This one too is extremely old (also 2008 I believe), and has fraying at the wire coming out of the adapter. I have had to do the whole taping it up, keeping it in a certain position with a hair clip etc. To keep it on.

I noticed that sometimes when my mac was plugged in, it was spontaneously just switching off even thought it had a full charge and was plugged in. It would do this continuously until I unplugged, and used without charge. Then I would have to reposition the charger wire to use it again.

This happened again today, so I used up my full battery while off charge. But now when I plug the charger back in, while the green light on the connector is coming on, my laptop is not responding whatsoever. Even when I push the little battery check button on the left, it doesn't light up (on the last dot) unless I unplug the connector.

I Also do not have an original apple battery (my laptip is old and I am broke, pls dont judge me! =P)

So now I'm not sure if it's my battery and/or the charger, and whether or not it's worth trying to get a new charger or getting a new battery too (although this one is only 9 months old)

I have tried various methods of getting the laptop to come back on (removing battery etc.) but because it has no charge left in it at all, i can't be sure which is the issue!

So I don't know what to do! Please help!

And please don't tell me I just need a new laptop altogether, not an option!

I am in a similar situation! What did you do?

I had to just bite the bullet and get a new one! I don't think you can get a genuine apple for such an old model any more, so I got one from an authorised apple retailer store, and had no problems after that!

So it wasn't the non apple battery, it was just the old battered charger!