MagSafe 1

You drink (buy into) the Apple kool-aid; you live with it (keep on buying).

RL

I have a couple of those adapters - both Magsafe 1 and 2. I haven't used the 1 yet but the 2 works fine. From Aliexpress - the listing is gone but looked like this:

• Input: AC 100–240 volts (V), 50/60 hertz (Hz)
• Output: DC 14.85V, 3.05A

• Input: AC 100–240 volts (V), 50/60 hertz (Hz)
• Output: DC 16.5V, 3.65A

• Input: AC 100–240 volts (V), 50/60 hertz (Hz)
• Output: DC 20V, 4.25A

The Magsafe 1 supplies are fractionally lower voltages/higher currents:

The Macbooks will have their own independently controlled DC-DC converter to charge the battery so the battery won't care what the input voltage is. If anything a higher voltage might help as it reduces the current and makes things run slightly cooler.

I wouldn't worry about it.

Theo

According to a video (***), linked in the comments of (**), MagSafe charger detects resistance at the connection with the Mac and, if indicates charger has the minimum required power, switches on at full power. Three resistances offered by Macs according to their preferred power input.

Then the Mac reads the power adapter ID from the connector and powers the Mac.

Finally a voltage controller and proper adapter ID allows battery to be charged. It also sends commands to switch LED on/off.

To be noted I don’t really understand electrical engineering. Here I am just trying to summarize few points appearing relevant to me.

I realized USB-C to MagSafe 1/2 adapters most likely provide a proper charger ID. Otherwise nobody would buy them. Do them also translate, for the USB-C PD side, voltage controls which allow current to be extremely low for one second after first contact with the Mac charging port?

Haven’t thought about it. Thanks.

Thanks for the references. Collecting together all relevant data is useful to me to better define the problem.

I currently use a 45W charger with MagSafe 1 cable. I may later switch to a Mac laptop requiring only 30W and with native USB PD.

Following up on my previous, I just read USB PD does power negotiation with low Initial power. So if MagSafe 1/2 adapter also implements the resistance check and sends proper PD signal to ramp up power it should be as safe as the Apple old solution.

Something I noticed is USB-C chargers at 20V are not exactly delivering the current as by Apple chargers specs you noted above. If upper/lower could it become a problem?

Also some of the (second hand) charges I am considering do implement Programmable Power Supply (PPS). I don’t know if any of the adapters also implement that.

Thanks. You gave the full answer but took me a while to realize it.

I read enough to have a better understanding of the technology stack now. Most useful source was Ken Shirriff’s disassembly account of MagSafe. And the comments to it spanning over more than a decade.

My cable connector reports an 85W charger even though it is connected to a

I expect that the charging circuit is already flexible as to the voltages and currents it can accept - it has to accept 6 different chargers (3x Magsafe 1, 3x Magsafe 2) with different voltages and currents.

As the charging is likely to be run by a microcontroller, I expect it will aim to find the sweet spot in terms of power it can pull - eg before it tries to pull 5A from a power supply only capable of 3A, it will try increasing the current gradually and at say 3.5A the voltage will start to sag (ie before the PSU completely cuts off due to overcurrent). A smart charger design will then back the current off a bit until the voltage has risen to its maximum - it works out that it can only pull 3A by observing the voltage/current curve for different current values.

I don't have any visibility into Apple's power supply design but I expect the worst that can happen is it doesn't work rather than blowing something up. But your own risk etc etc. As we know there's a genuine PSU outputting

I doubt it. That's mostly for superfast phone charging, where you match the power supply output to the current battery voltage - ie skipping the onboard DC-DC converter and instead using the much better heatsinked external converter. I don't think enough chargers are doing PPS up to 20V to make it an option for these Magsafe adapters.

(I've been using my adapter on a non-standard 130W Dell PSU that only does

Theo

Found one account of a 110W , 18.5V Mac Mini charger used with a MagSafe 1 cable attached to it. It works. MagSafe 2 goes up to 20V which is the same as offered by USB PD. But not MagSafe 1. Clearly there is some leeway on voltage accepted by our Apple devices. But not too much because 29W ,

Found account of a knockoff MagSafe 1 cable, attached to an original charger, keeping voltage permanently at charging power. There is even a video of the adapter head I am considering, USB-C to MagSafe 1, sparking when in close contact with a piece of metal. Specs were never published but it still surprises me considering power ramp up should be controlled entirely by the charger. Not the connector.

With a MagSafe 2 equipped Mac I assume. My MagSafe 1 equipped MacBook Air’s battery with 1,054 cycles still shows Normal status. Uncertainty about the slight over voltage, and possible inhibition of low power detached / fully charged mode, makes me a bit nervous to try.

New USB-C travel power adapter is ungrounded and double shielded. New USB-C to MagSafe 1 cable is also very cheap. While charging the mouse pointer jitters and acts erratically. Stops if I unplug the charging cable. A first in my experience.

I have read grounding issues may cause that. To note power adapter seems not to cause any problems with other devices. Anything I can do to improve?