Does anyone understand the failure mechanism of magsafe type power connectors?  - Page 1
Forum section: electronics / projects

author: e100
author_rank: Frequent Contributor
timestamp: May 25, 2018, 08:33:19 am
content: Magsafe is a proprietary electrical connector popularised on Mac computers and according to wikipedia derived from the magnetic breakaway connectors used on fat fryers in Japan.https://en.wikipedia.org/wiki/MagSafeIt uses a series of pogo pins with a magnet to hold the two connector halves together. To make the connector reversible it has two power pins surrounded by two ground pins. There's a signal pin in the middle which is used to drive the LED indicator. There are only two wires in the actual cable that runs to the power supply.Over a period of years or months the plug gets progressively hotter while charging, presumably because of increased electrical resistance. Visible charring only appears on the two outer ground connectors. The two inner power connectors look fine. I've seen this problem twice with the same characteristic burn marks only on the ground connectors. Does anyone know why this is so?

author: abyrvalg
author_rank: Frequent Contributor
timestamp: May 25, 2018, 08:55:01 am
content: This is a pure speculation, but: I suspect a spring inside one of the gnd pogos is weared and broken resulting in two things: 1.higher resistance through this pin (so higher temp), 2. higher current through the other gnd pin (so higher temp there too)

author: Electro Detective
author_rank: Super Contributor
timestamp: May 25, 2018, 09:05:49 am
content: AFAIK it's usually dust and gunk that starts it, if you keep the contacts clean the problems disappearIIRC...I use contact cleaner lubricant on those connectors, it cleans and lubes the springy Magsafe contacts so they don't seize upThe crappy Magsafe cables on Macs are another 'failure' story...

author: bd139
author_rank: Super Contributor
timestamp: May 25, 2018, 09:08:02 am
content: Seen this numerous times before. The connector is NOT durable at all. It can get hot enough to melt the plastic in the connector.I suspect it's oxidation or change over time in the properties of the metal leading to increased resistance and power dissipation. At some point, no amount of decrudding improves it so it's IO board swap and new charger time.I actually had one circa 2008 MBP where the left IO board was badly burned from the heat transfer through the connector. I think that was coffee related though because it smelled funny.Charger cable strain releif. Now that's a turd. They should have reserved the name Firewire for the chargers.

author: Electro Detective
author_rank: Super Contributor
timestamp: May 25, 2018, 09:18:28 am
content: hmmm, sounds like a few members here have had to deal with Mac-kered adapterspractical innovative gadgets, engineered to last for...just before the next Mac model release?IMHO, Magsafe is THE way to go for portable devices, if manufactured properly, with beefed up pins and better lubed springsBut that's not going to happen any time soon

author: Rerouter
author_rank: Super Contributor
timestamp: May 25, 2018, 09:27:45 am
content: When you disconnect one of these, you are more likely to unplug it off to a side than straight out. Equally if there is the offset mass of the cable one end will not be perfectly centered on its mating surface, heating up and oxidising faster.

author: bd139
author_rank: Super Contributor
timestamp: May 25, 2018, 09:31:27 am
content: Quote from: Electro Detective on May 25, 2018, 09:18:28 amLenovo's answer is better. When you fall over the cable and the machine hits the floor it still works. That covers all cases of "I dropped it", not just the "I fell over the cable" vector of death.Like when I fell asleep with my absolutely stacked top end 15" rMBP on my lap and cost me a pretty penny for a new lid/screen assembly

author: rachaelp
author_rank: Unknown
timestamp: May 25, 2018, 11:45:41 am
content: Quote from: Rerouter on May 25, 2018, 09:27:45 amI just sat here and tested how I unplug mine, I grab it and pivot it along its horizontal axis slightly as I pull it away. This makes them all disconnect at roughly the same time and very easily. Unplugging it off to one side or the other isn't actually very easy as they sit slightly recessed and it actually takes quite a bit of pressure to make it pull away in this manner. Maybe if people just pick up their laptop and walk away and rely on the Magsafe to just break away as the cable goes tight then this might happen, but not when taking it out how it is intended to come out.Looking at the connectors on mine now, there is zero visible oxidisation and it all stays pretty cool. I've not actually had any Magsafe connectors exhibit any issues. Maybe some of the issues are on chargers bought from very cheap eBay sellers and maybe they aren't up to the required quality? I'm not saying there haven't been issues with genuine Apple ones too of course.Best Regards,Rachael

author: Rerouter
author_rank: Super Contributor
timestamp: May 25, 2018, 12:07:57 pm
content: I can only work off the images shown,Being negative it could suffer from electroplating of undesired metal ions from water vapour, but the way it goes out in a ring seems odd.The other part why i think mechanical / blackening is how messed up the surfaces are on the cups of those 2 outer pins, That level of pitting to me would be from poor contactAs its so much pressure to insert, can the connection be partially made if not careful (Never owned a magsafe charger)

author: rachaelp
author_rank: Unknown
timestamp: May 25, 2018, 12:18:47 pm
content: Quote from: Rerouter on May 25, 2018, 12:07:57 pmCertainly in the case of mine there is zero pressure to insert, it's not an interference fit, and can you bring it close and the magnet pulls it into place easily. I can see how if it were somehow being prevented from going in smoothly then you may be right and it may not make a good contact. Maybe damage to the connector or spillages etc causing a build up of gunk on it may be a factor, or cheap clone chargers which have different tolerances than required affecting the mechanical fit?

author: e100
author_rank: Frequent Contributor
timestamp: May 25, 2018, 02:52:53 pm
content: Quote from: abyrvalg on May 25, 2018, 08:55:01 amThat sounds plausible. I've replaced both connectors just in case the damage on one has been causing damage to the other.

author: e100
author_rank: Frequent Contributor
timestamp: May 25, 2018, 03:08:25 pm
content: Quote from: Electro Detective on May 25, 2018, 09:18:28 amHas anyone done it right? There don't seem to be many examples of pogo pin type connectors that have stood the test of time.Is a wiped contact the only way to go?All the stuff I do is iterative so I'm forever making and breaking connections. The idea of a multi-pole snap together connector would be awesome for joining modules, providing that the reliability is there.

author: Gregg
author_rank: Super Contributor
timestamp: May 25, 2018, 07:03:45 pm
content: It is a basic design flaw. The contacts are shaped such that one side is cupped to trap gunk. The contacts do not slide against each other to slough off gunk. The contacts are quite small for the amount of current they need to carry considering they are not protected in any way.If you look at contacts that last like a relay, both sides are convex and slide across each other a little as the contact is made. Many relays are within a capsule of some sort to keep dust and dirt to a minimum.Other plug and socket power connectors usually slide across the contact surfaces as they are inserted and removed.Apple has a long history of eschewing ruggedness and reliability for more marketable aesthetics such as thin and light weight. It is the price paid for belonging to the apple community which has a long history of not complaining enough about defective engineering.

author: jbb
author_rank: Super Contributor
timestamp: May 25, 2018, 08:12:53 pm
content: I think there's a luck element. Mine is still going strong after 7 years, and i haven't been too careful about alignment or cleaning. I haven't applied any grease.The cable is doing OK because I'm really careful when I store it. Those fold-out white ears you can allegedly wrap the cable around are worse than useless in my book.I wish Apple would select a slightly more durable cable jacket and really up their strain relief game.

author: Electro Detective
author_rank: Super Contributor
timestamp: May 25, 2018, 10:50:19 pm
content: FWIW I've come across a lot of them, own a few rescued ones myself, and the brushoff, clean, lube and working the pins up and down method -usually- sorts them out electricallyEven if they look ok and functional, I do it anyway, perhaps that's why some of my batteries last ages, even if tired to begin withSometimes there's an intermittent hidden short in the cable somewhere, which I assume would assist in a few problems and heat at the connector endsI usually feel for bumps or soft spots along theal dente spaghetti gradecable to try track down the 'not so sweet' spotI'll have to rig up some some sort of interface 'one day' () so I can use a multimeter at the end to make the task easierrather than just using The ForceBTW folks, I'm referring to the real deal Apple Magsafe adapter/chargers,if it's a OHL Apple knockoff I don't botherand order/recommend an original replacementIf there's a knockoff out there I'm unaware of that's better quality, please don't be shy to comment below

author: helius
author_rank: Super Contributor
timestamp: May 25, 2018, 10:57:12 pm
content: Quote from: Electro Detective on May 25, 2018, 10:50:19 pmYes, they can readily develop shorts because there is only one layer of material between the inner and outer conductors. A common, dirt cheap "zip-cord" lamp wire is better protected from short circuits.

author: stmdude
author_rank: Frequent Contributor
timestamp: June 02, 2018, 07:14:36 pm
content: Quote from: bd139 on May 25, 2018, 09:31:27 amYea, but now you have a broken floor and an intact laptop.

author: Electro Detective
author_rank: Super Contributor
timestamp: June 03, 2018, 10:19:31 am
content: Quote from: stmdude on June 02, 2018, 07:14:36 pm...and wheel and deal with the 'not too impressed'floor loving partner

author: David Chamberlain
author_rank: Frequent Contributor
timestamp: June 03, 2018, 11:48:40 am
content: Past macbook owner here. Same thing for me. One of the power pins got gunked up, made bad contact and proceeded to melt itself.Ill admit i never bothered to check it for two years but then why should I? The non tech savvy consumer sure as hell won't.