Apple Magsafe 18.5v?

[iamdarkyoshi]

Hello all, I've gotten a cheap chinese 3rd party macbook charger that puts 18.5v straight on the pins of the magsafe connector, and it does actually charge macbooks.

 

My question is if this is normal. The PSU is an 85W unit, rated at only 18.5v out. The genuine one says 16.5-18.5v, not sure how it switches voltages as there is only 2 wires going to the PSU. 

 

 

So in all, are ALL macbooks safe with 18.5v on their connector? Because up until now, I've always thought they were 16.5v only. Seeing as 18.5 might be a possibility, I want to add them to my universal charger...

[Mira Yurizaki]

7 minutes ago, iamdarkyoshi said:

Hello all, I've gotten a cheap chinese 3rd party macbook charger that puts 18.5v straight on the pins of the magsafe connector, and it does actually charge macbooks.

 

My question is if this is normal. The PSU is an 85W unit, rated at only 18.5v out. The genuine one says 16.5-18.5v, not sure how it switches voltages as there is only 2 wires going to the PSU. 

 

 

So in all, are ALL macbooks safe with 18.5v on their connector? Because up until now, I've always thought they were 16.5v only. Seeing as 18.5 might be a possibility, I want to add them to my universal charger...

The voltage depends on the wattage of the power supply. 18.5V is used on 85W chargers. However this is the maximum voltage, so I'm inclined to believe that plugging in an 18.5V charger into a Macbook Air, which comes with a 14.5V 45W charger, is safe.

 

If it wasn't, woo boy.

 

EDIT: So I found out how the chargers work (from http://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html):

1. The charger provides a very low current (about 100 µA) 6 volt signal on the power pins (3 volts for Magsafe 2).
2. When the Magsafe connector is plugged into the Mac, the Mac applies a resistive load (e.g. 39.41KΩ), pulling the power input low to about 1.7 volts.
3. The charger detects the power input has been pulled low, but not too low. (A short or a significant load will not enable the charger.) After exactly one second, the charger switches to full voltage (14.85 to 20 volts depending on model and wattage). There's a 16-bit microprocessor inside the charger to control this and other charger functions.
4. The Mac detects the full voltage on the power input and reads the charger ID using the 1-Wire protocol.
5. If the Mac is happy with the charger ID, it switches the power input to the internal power conversion circuit and starts using the input power. The Mac switches on the appropriate LED on the connector using the 1-Wire protocol.

[iamdarkyoshi]

4 minutes ago, M.Yurizaki said:

The voltage depends on the wattage of the power supply. 18.5V is used on 85W chargers. However this is the maximum voltage, so I'm inclined to believe that plugging in an 18.5V charger into a Macbook Air, which comes with a 14.5V 45W charger, is safe.

 

If it wasn't, woo boy.

I'll have to try this

[Mira Yurizaki]

2 minutes ago, iamdarkyoshi said:

I'll have to try this

Actually if it's a Chinese knock off, don't use it with a Macbook that uses a different wattage. If you plug in say a Macbook Pro knockoff 85W charger into a Macbook Air, you're going to blow it up because it probably won't go to 14.5V and instead feed the Macbook Air 18.5V.

 

Also if the official charger says 16.5V-18.5V, it probably won't charge a Macbook Air. It won't supply high voltage, but it can't charge it since 14.5V is not part of its spec.

[iamdarkyoshi]

2 minutes ago, M.Yurizaki said:

Actually if it's a Chinese knock off, don't use it with a Macbook that uses a different wattage. If you plug in say a Macbook Pro knockoff 85W charger into a Macbook Air, you're going to blow it up because it probably won't go to 14.5V and instead feed the Macbook Air 18.5V.

Well I've plugged a knockoff charger into a macbook air:

 

And it does appear to be charging...

[Mira Yurizaki]

2 minutes ago, iamdarkyoshi said:

Well I've plugged a knockoff charger into a macbook air:

 

And it does appear to be charging...

Hm.

 

It could also be that the label is whatever, because you know they submitted their units to the FCC and CE for certification :3

[iamdarkyoshi]

1 minute ago, M.Yurizaki said:

Hm.

 

It could also be that the label is whatever, because you know they submitted their units to the FCC and CE for certification :3

 

Alright I'm slicing the wire open and measuring voltages, brb...

[Mira Yurizaki]

2 minutes ago, iamdarkyoshi said:

 

Alright I'm slicing the wire open and measuring voltages, brb...

"WARNING: This device may not cause harmful interference"

 

Okay, thanks for warning me!

[iamdarkyoshi]

5 minutes ago, M.Yurizaki said:

"WARNING: This device may not cause harmful interference"

 

Okay, thanks for warning me!

Yup, 18.5V straight into the old ass MBA

[Mira Yurizaki]

6 minutes ago, iamdarkyoshi said:

Yup, 18.5V straight into the old ass MBA

Now I'm tempted to believe Apple should be given credit here by supplying a charging circuit that is all "eh, whatever" or they use a boost converter to ensure some maximum voltage.

[iamdarkyoshi]

2 minutes ago, M.Yurizaki said:

Now I'm tempted to believe Apple should be given credit here by supplying a charging circuit that is all "eh, whatever" or they use a boost converter to ensure some maximum voltage.

Thats what i'm wondering... But is it the same on all units?

[Mira Yurizaki]

1 minute ago, iamdarkyoshi said:

Thats what i'm wondering... But is it the same on all units?

Wouldn't surprise me.

 

Active PFC power supplies don't have a 115V/230V switch because the PFC circuitry ensures the rest of the system works with 230V. In the case of a PSU with a switch, the 115V input goes through a voltage doubler.

[iamdarkyoshi]

3 minutes ago, M.Yurizaki said:

Wouldn't surprise me.

 

Active PFC power supplies don't have a 115V/230V switch because the PFC circuitry ensures the rest of the system works with 230V. In the case of a PSU with a switch, the 115V input goes through a voltage doubler.

I'll be damned...

Newer macbook air

[Mira Yurizaki]

3 minutes ago, iamdarkyoshi said:

I'll be damned...

 

Newer macbook air

I guess it's safe to say Apple designed their charging circuit with all the bells and whistles.

 

Still, wouldn't really trust a Chinese knock off charger...

[Unimportant]

Perhaps relevant: http://www.righto.com/2016/03/counterfeit-macbook-charger-teardown.html