Using a power adapter/supply with higher/lower output than original

[y_p_w]

I’m just curious how others have looked into this. Apple used to have its proprietary MagSafe power adapters that came in multiple output levels. The ones I’ve had were rated at 60W but the list price was the same for the 85W version, which some recommended since they were all compatible and with the rationale that it should run cooler and last longer. They also had this special version for use with an obscure power port found on some passenger airlines, but where they said it would only provide power for active use but wouldn’t charge the battery.

With USB-C, there’s a lot of flexibility. Almost too much. Some computers can deal with 5W. Others just don’t accept it at all. I know with one Lenovo laptop in my house there’s a warning. It came with a 65W power adapter that no longer works. It seems that under 45W is where there’s a message at power on in that it’s a lower power than recommended and requires a button press to continue. But 30W seems to be adequate, although it might charge slower if the battery is drained. We typically have it plugged in nearly all the time.

I’ve taken to using a USB-C power pack with an 18W rated output to at least slow down the draining of the battery.

My wife lost the rather expensive higher powered Apple OEM power adapter and cable on her Mac and just replaced it with something cheap - maybe 45W. But it’s been working fine. I occasionally use a 45W Anker power adapter on a Mac that came with a 67W USB-C power adapter and that hasn’t created any issues so far.

More recently I’ve been using a Chromebook away from home to stream video to a TV. I typically keep the 45W USB-C power adapter that came in the box, at home. So I’ve tried a variety of power adapters like a 30W Apple or a 20W generic one (label says made by Rewoda) and the status says something about the power being unreliable, although (if the battery is under 100%) it usually will still charge up to 100% while being used. I did try using the USB-C port from my Anker 321 cube power adapter and surge protector. It says it’s rated at 20W for USB-C, but the other night it was slowly dropping charge level even though it indicated that it was connected to power. I switched to the separate 20W adapter and it started charging the battery again.

 

[andrew_j]

I use my Apple Mac book 85w USB c charger on anything with usb port without issue. From cheap device, Chromebook , older tablets , iPhones etc.

 

[wag123]

What is important is the the regulated voltage and the minimum current (amps) that the device requires. Watts = Volts x Amps. If 2 power supplies have the same regulated voltage you can substitute a higher wattage power supply for a lower wattage power supply, but not the other way around. The device will only draw the current it needs from the higher wattage power supply..

 

[Hall]

The device will only draw the current it needs from the higher wattage power supply

This is the key. A power supply doesn't "push" whatever wattage it wants, it only pushes what the device it's charging "pulls" or wants.

 

[y_p_w]

What is important is the the regulated voltage and the minimum current (amps) that the device requires. Watts = Volts x Amps. If 2 power supplies have the same regulated voltage you can substitute a higher wattage power supply for a lower wattage power supply, but not the other way around. The device will only draw the current it needs from the higher wattage power supply..

USB-C is very different though. It’s got multiple voltages and current ratings that are negotiated with the device and the power supply. The 30W one I mentioned has on that’s 20V at 1.5A. But I’ve gotten some computers to accept a 5W supply using a USB-A to USB-C cable. But 5W just slows down the charge level drop

There are some oddball pairings that don’t work because of the bidirectional nature of USB-C. I can’t get a mobile computer with USB-C to charge one of my USB-C power packs with a USB-C only cable. It always treats the power pack as a supply and tries to pull power from it. But a USB-A to USB-C cable is always treated as power to the USB-C end. So use one of those and I can get a computer to charge the power pack.

 

[y_p_w]

This is the key. A power supply doesn't "push" whatever wattage it wants, it only pushes what the device it's charging "pulls" or wants.

That part I get. But there are all these permutations with USB-C. I’ve got several USB-C/USB-A power packs where USB-C is the only way to charge the pack, but also an output. And there’s no way to control it. Plug it into a mobile computer and the only way is power into the computer, even if there’s a higher powered power adapter connected and powering the computer.

 

[spackard]

They are programmable power supplies, a bit of new technology. The programming happens in the first 0.1 second connection to a device, if I recall correctly. If you want to read what the source and sink agreed upon you can use this device. The brand, ChargerLAB, has several YouTube videos testing different power supplies.

You’re safe buying the Apple 85W supply. It may be a bit larger physically. Apple in general makes high quality supplies.

I don’t particularly like the multiport USB-C chargers yet. But that’s another discussion.

 

[y_p_w]

They are programmable power supplies, a bit of new technology. The programming happens in the first 0.1 second connection to a device, if I recall correctly. If you want to read what the source and sink agreed upon you can use this device. The brand, ChargerLAB, has several YouTube videos testing different power supplies.

You’re safe buying the Apple 85W supply. It may be a bit larger physically. Apple in general makes high quality supplies.

I don’t particularly like the multiport USB-C chargers yet. But that’s another discussion.

Multiport USB anything can be odd. I have an older Mac with two USB-A ports and I can see what it "provisions" as 5V output. I can plug in an iPhone or iPad and it says 2100 mA for just that. But if I connect two, it becomes 1500 mA each.

What I've got are combined USB-A and USB-C power sources. They may or not be independent circuits, but I suspect not. I'm thinking that if there's anything USB-A connected on that Anker 321, it probably reverts to 5V, even though the specs say that the USB-C is more or less independent. And it says up to 2.4A on each USB-A port but not double that if both are used.

I do have one that's listed as 60W total with 45 to USB-C and 15 to USB-A. I believe that's using separate circuits.

 

[wrcsixeight]

Dont under estkmate the effect.of the cables, and the conditikn of their connectors, themselves, in achieving higher charge rates.

I have a 10' high quality usb c cable.
With my usb c meter at the far end of this 10' cable, it reads 4.610v and 1.021 amps.

With my usb c meter attached to 7" usb cable to power suppky, it reads 5.09v, and 1.623 amps into my well depleted phone baTtery.

Get a usb meter,
I like this one.

About 10$ on ebay.

 

[y_p_w]

Dont under estkmate the effect.of the cables, and the conditikn of their connectors, themselves, in achieving higher charge rates.

I have a 10' high quality usb c cable.
With my usb c meter at the far end of this 10' cable, it reads 4.610v and 1.021 amps.

With my usb c meter attached to 7" usb cable to power suppky, it reads 5.09v, and 1.623 amps into my well depleted phone baTtery.

Get a usb meter,
I like this one.

About 10$ on ebay.
View attachment 154830

I suspect that some of my USB-C cables don't work consistently because of excessive resistance. It might start charging for a few seconds or a few minutes and then says it's no longer charging even though it might still maintain a data connection (if connected to a computer).

I've seen a few USB-C cables listed as 2.4A rated, but as far I know, the minimum requirement is 3A. I have a few (from Monoprice) that say they're rated at 5A and there's supposed to be some sort of signaling circuit in the cable to indicate it. One is 3 feet and really thick. As in so thick that it just doesn't like to bend easily. I feel like if I try to fold it like most cables it's going to be permanently deformed so I curl it in a circle. But others say they're 5A rated but the cable (even with a fabric jacket are thinner, like one I have that's 10 ft long.

 

[Carmudgeon]

Type-C, being the holy grail of connectors, can carry data connections from the 480Mbps of USB 2, to the 40Gbps of Thunderbolt 4, and power levels from 5W or less, to 240W under the latest spec, as well as video and audio.

To do all those things, it has to be smart.

There are nine pins in a USB-A connector. A Type-C connector has 24 pins.

Two of those pins are dedicated to a communication channel, which helps determine the orientation of the plug (since it's reversible), when something is connected, what roles each connected device plays, and negotiates the level of power supplied. And more, including role switches.

Nothing happens until the connected devices talk to each other, or in the case of a "dumb" device that simply needs to draw some power, has the necessary resistors to signal to the source that there is something connected on the other end.

(Keep in mind that Type-C doesn't automatically imply the presence, or use of the PD power protocol, like most presume. There is little reason to put a PD controller inside of a simple device like a flashlight, or similar, that has onboard charging with modest draws. It simply needs to have the necessary pulldown resistors in its connector to signal an intelligent Type-C power source that something is connected, yet it's a simple and cheap step that many don't implement properly, hence dumb products that have Type-C ports, really in name only, that will only charge from Type-A sources.)

Those dumb devices will always work with Type-A sources because it is also dumb, and provides constant live voltage in the connector as long as the host is powered on. Which is why those aftermarket magnetic quick-connect or breakaway connectors with exposed contacts aren't considered to be smart ideas.

Those multi-power chargers can behave quirkily, despite having outlines of how their power is supposed to be distributed amongst the ports in different situations, and I don't believe it's something that is covered deeply, if at all, in the spec. Some who are into these kinds of hardware aren't comfortable with them either.

A 3A cable is the minimum that is spec compliant, even if it may only carry data at USB 2 speeds. That's one portion of the spec that wasn't sacrificed to cost considerations. The 240W cables defined under PD 2.1 are still only rated at 5A, but at 48V, instead of the 20V of the older 100W spec. Anything above the baseline 60W must have e-marker chips.

It's a complex recipe, and implementations can be less than perfect even from those with the intent and resources to do it properly. Those companies that are willing to bend the rules, and cut corners add to the risks.

 

[bunnspecial]

The old Magsafe Apple bricks went down as low as 45W as supplied with the MacBook Air. Realistically the 13" MBP will generally do fine with a 45W unless its really being hammered and then might either charge slowly or not charge at all while being booted.

The 15" and 17", both with the bigger screens and usually more powerful processors, can be a different beast. If you plug a 17" into a 45W brick, you probably can't power it up unless there's some charge in the battery. It probably won't charge unless it's asleep, and the battery may even drain in use(it can do that if you're really hammering on it with an 85W too, but it's difficult to do). I've run my 15" 2015 on a 45W a fair bit and it will sometimes charge slowly while I'm using it(think 1-2% an hour) or sometimes just go into power only.

The 60W will usually handle any size of MBP decently well, although the 17s still like to see some charge on the battery before they will power on when connected to one.

On my desk at work is a USB-C dock that I have a 30W brick plugged into. My 13" M1 MBP generally won't charge while I'm using it, but will slowly charge when asleep. If I start the day at say 50%, it will usually be charged all the way by the end of the day but that includes a few stretches of an hour or two away from my desk.

For the most part the biggest charger available is usually the way to go, but they do get physically larger/heavier as you move up. The old Cinema and Thunderbolt displays have 85W chargers built in even though they will work just fine with any laptop that can physically interface to them, and most USB-C PD docks with integrated chargers will be 85W.

BTW, the whole thing with draining the battery is why you always want to have a battery in your computer that can hold and supply at least some charge, at least when it comes to Macs. This has been true back at least to the G4 era of laptops. If the computer doesn't see a battery present, it will drop into "reduced performance" mode. Normal/high performance depends on using the battery to smooth out any sudden spikes in power consumption. From what I've seen, even an 11" MBA without a battery plugged into an 85W charger will run with reduced performance.

 

[y_p_w]

The old Magsafe Apple bricks went down as low as 45W as supplied with the MacBook Air. Realistically the 13" MBP will generally do fine with a 45W unless its really being hammered and then might either charge slowly or not charge at all while being booted.

The 15" and 17", both with the bigger screens and usually more powerful processors, can be a different beast. If you plug a 17" into a 45W brick, you probably can't power it up unless there's some charge in the battery. It probably won't charge unless it's asleep, and the battery may even drain in use(it can do that if you're really hammering on it with an 85W too, but it's difficult to do). I've run my 15" 2015 on a 45W a fair bit and it will sometimes charge slowly while I'm using it(think 1-2% an hour) or sometimes just go into power only.

The 60W will usually handle any size of MBP decently well, although the 17s still like to see some charge on the battery before they will power on when connected to one.

On my desk at work is a USB-C dock that I have a 30W brick plugged into. My 13" M1 MBP generally won't charge while I'm using it, but will slowly charge when asleep. If I start the day at say 50%, it will usually be charged all the way by the end of the day but that includes a few stretches of an hour or two away from my desk.

For the most part the biggest charger available is usually the way to go, but they do get physically larger/heavier as you move up. The old Cinema and Thunderbolt displays have 85W chargers built in even though they will work just fine with any laptop that can physically interface to them, and most USB-C PD docks with integrated chargers will be 85W.

BTW, the whole thing with draining the battery is why you always want to have a battery in your computer that can hold and supply at least some charge, at least when it comes to Macs. This has been true back at least to the G4 era of laptops. If the computer doesn't see a battery present, it will drop into "reduced performance" mode. Normal/high performance depends on using the battery to smooth out any sudden spikes in power consumption. From what I've seen, even an 11" MBA without a battery plugged into an 85W charger will run with reduced performance.

My battery on my 13” Unibody intermittently failed and it wouldn’t start at all, even with the battery connector pulled and the MagSafe power adapter connected and with the indicator light on. I surprisingly got the battery replaced at an Apple Store last year and it works perfectly now. They did claim that the drive (a WD Blue 1 TB SSD) was failing but I understood that failure reporting happens with any non OEM drive.

The weirdest was the MagSafe Airline Adapter that worked with 15V EmPower ports that some airlines provided. I heard that Macs would never charge the battery when one was connected and working. The power would only be used for active power needs. It also came with a lighter plug adapter so I think it only needed 12V.

I would never have trusted an aftermarket MagSafe power adapter. I heard there were a few on the market that used an actual MagSafe connector as a “donor”, but for specific setups that Apple didn’t provide.

 

[bunnspecial]

My battery on my 13” Unibody intermittently failed and it wouldn’t start at all, even with the battery connector pulled and the MagSafe power adapter connected and with the indicator light on. I surprisingly got the battery replaced at an Apple Store last year and it works perfectly now. They did claim that the drive (a WD Blue 1 TB SSD) was failing but I understood that failure reporting happens with any non OEM drive.

The weirdest was the MagSafe Airline Adapter that worked with 15V EmPower ports that some airlines provided. I heard that Macs would never charge the battery when one was connected and working. The power would only be used for active power needs. It also came with a lighter plug adapter so I think it only needed 12V.

I would never have trusted an aftermarket MagSafe power adapter. I heard there were a few on the market that used an actual MagSafe connector as a “donor”, but for specific setups that Apple didn’t provide.

I have one of those around here somewhere-on a 12V car outlet it just makes the battery drain less slowly. Never saw the plug on an airplane so have no idea.

There are a lot of counterfeit genuine-looking Magsafes out there. One 100% reliable test I've used is to plug them in. Genuine Magsafe adapters, when connected, will "handshake" with the computer for a moment before starting to charge. If you watch a genuine one, it will take a second or so for the LED to come on after plugging in. The counterfeit ones without fail will come on immediately.

 

[y_p_w]

I have one of those around here somewhere-on a 12V car outlet it just makes the battery drain less slowly. Never saw the plug on an airplane so have no idea.

There are a lot of counterfeit genuine-looking Magsafes out there. One 100% reliable test I've used is to plug them in. Genuine Magsafe adapters, when connected, will "handshake" with the computer for a moment before starting to charge. If you watch a genuine one, it will take a second or so for the LED to come on after plugging in. The counterfeit ones without fail will come on immediately.

The Mac supposedly controls real MagSafe indicator lights.

I had a really bizarre thing happen a couple of times, when I plugged in a USB cable - actually a knock-off Lightning cable. Just went completely batty. The screen turned off and the indicator light on the MagSafe connector started blinking amber until it just went out and the whole computer just locked up with no way to turn in on or off. The battery indicator light on the side didn't turn on either when I pressed the button.

I could hear a faint hum coming from board so it was powered on some way. I tried to turn off by pressing on the power button to no avail. Then I tried to go to an Apple Store and they told me I would either need an appointment or get placed on a waiting list the next day when they opened. I just got over my fear, grabbed a #0 Phillips screwdriver, and went in where I just pulled out the battery connector to the logic board and plugged it back in. It started up normally when I pressed the power button. At that point I was confident enough to change the drive or memory in the future when I saw easy it would be. The same thing happened another time (slightly different things with the lights), and by then I had no hesitation taking off the bottom and disconnecting the battery.

And I've participated on Apple's user support forums. Anyone talking about taking apart a Mac (with limited exceptions) can expect to get the discussion shut down. I've even posted a link to Apple's own public instructions on how to replaced the hard drive and my post was removed. I've even had a few suspensions where I wasn't allowed to post. Made a mistake once where I thought maybe I forgot post what I intended and I reposted. Found a long term suspension for months as a result. That can be a fun place, but they control what people can talk about when it comes to DIY repair.

 

[benjy]

good info as i have 2 older laptops with batteries that wont charge, swapped adapters around helped a while but only works on home power now, but only one laptop leaves the house for use on my car + thats the newest one i am using now a 17" HP