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Hi13 original Charger KEYU KA1440 is dangerous!

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artowi|Post time:8-9-2017 02:29:41 View:3627|Reply:62

ZenBalancer| Post time 8-2-2017 03:13:36 | Show all posts
Edited by ZenBalancer at 8-2-2017 12:18
Pajero replied at 7-31-2017 13:20
Hi All

There is a very interesting analysis of the problem by Artowi in this thread http://forum.ch ...

I'll throw this in. Isn't an assumption that using 5v peripheral will make the Hi13 stuck on 5v VBUS? There is a working dongle/hub allowing the Hi13 to charge as at 12v while supplying 5v to anything connected to the dongle simultaneously, but that might be just the dongle chip doing the work.

I connected a normal 2.0 USB flash stick to the TypeC via OTG. It worked fine, so 5v confirmed. And at some point used the Aukey recommended essentials charger. The only thing that I did with the Hi13 is sleep-mode many times in-between. Ah.. I forgot that the theory is that the original charger doesn't communicate the voltage..

So the dongle might actually save the situation as well.. always using the dongle in-between to charge with the original Chuwi adapter because the dongle passes on the 12v to Chuwi and the dongle USB TypeA/full-size is always 5v. So the Hi13 never needs to go to 5v. Correct?

Edit: That's about the dongle confirmed by Emily to work with the Hi13, and also charge it simultaneously with any connected charger, and isn't just a passive OTG thing.

Or can the single charging TypeC of the dongle/hub also be stuck at 5v if connected to a 5v charger? And then the original charger connected to it?

Edit: typo.
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artowi| Post time 8-2-2017 05:52:55 | Show all posts
With USB3.1 and PD things are more complicated compared to earlier USB2.0

When you insert a plug to the USB-C and measure the VBUS there will be no voltage from the Hi13 and the pins just seem 'disconnected'  

If you want to get 5V out from the Hi13 you need to connect a resistor between the USB-C PIN named 'CC' and GND.  This will tell the EJ898A chip you need power and by value of resistor you can tell what your maximum power consumption will be.  By pulling down with 36kOhm you request USB-standard power, by 10kOhm you request up to 1.5A and with 4.7kOhm you can demand up to 3A.

I slaughtered the original adapter cable and with no resistor there will be no voltage on VBUS, with 10k I get the 5V up to 1.5A - everything fine.

Once you pull out the connector the EJ898A will immediately will shut down power supply.

If you are the one providing power you should connect a resistor between CC and +5V and by the value of resistor you can tell the other side how much current you could provide.

All this only applies to voltage of 5V only.

Neiter side must apply any voltage greater 5v unless the CC wire is used for digital communication with data packages sent with checksum both ways so voltage never is increased unless both sides are confident they made a deal - a great deal - the best deal ever ;)  (oops, no politics)

The 2 big problems of KEYU charger:   

1)  12 V are applied to VBUS no matter what.  This is not ok.
2)  the resistor to connect with CC pin does not connect to 5V because there is no 5V available but to 12V.

This may be even the greater problem.   CC is a input pin which usually never should see a voltage greater 5V.   Pulling the CC pin to 12V may be a violation of the 'absolute maximum rating' of the EJ898A CC input pins.  Unfortunately there is no Datasheet for the EJ898A available otherwise it would be easy to check if 12V could be tolerated.

If the pin is not allowed to see 12V there may be a so latch up ( https://en.wikipedia.org/wiki/Latch-up ) which will burn the chip and this explenation seems absolutely plausible with the literally burned chips (chip case popped open) I found on my 2 mainboards.

So as long as the EJ898A is alivea and ok it does not seem that a voltage could persist after the USB-C connector was removed. Right after pulling the connector out the VBUS will be switched off.

Quite helpful explenation on the power issue can be found here:  http://www.androidauthority.com/ ... 1-explained-656552/

I still was seeking for plausible explenation on what burns the EJ898A and pulling CC to 12V and not 5V as necessary now is my best bet.



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MrMkayMan| Post time 8-2-2017 06:00:19 | Show all posts
Edited by MrMkayMan at 8-2-2017 07:02

Glad I came across this page when searching for Hi13 accessories. Ordered the Aukey USB C charger. I charged my Chuwi Hi13 only 2 times, should I be afraid to charge it again? Or can I charge it safely now, after Windows has booted. I did use, and will use the USB C port only to charge. Every other connection I use the micro usb for.

I was a bit sceptical about buying a cheap 'alternative' brand after some bad experiences in the past, but we live in 2017 now, and still somehow things have not been much improved. Chargers that destroy products Hope I'm not too late, other than that, the thing is doing great, a bit sluggish in screen rendering performance, but the sharp screen makes up for it.

tldr: Is there a safe way to charge with the standard keyu charger untill I receive the proper Aukey charger?
What is official reaction from Chuwi regarding this charging issue? I mean they should at least come out with a warning for potential buyers, if I did not come to this forum by accident, I would never saw this issue and continue to use the crappy charger.
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artowi| Post time 8-2-2017 07:31:36 | Show all posts
update for the  geeks :

Other brand USB PD controller chip from Rohm and TI brand have datasheets available for anybody to download and the CC pins are specified with 'absolute maximum rating' (beyond which damage will occur) is -0.3 to +6V     The KEYU charger applies +12V

I contacted Etron, the manufacturer of the EJ898A chip asking for a datasheet.  They will not be happy to find their product associated with burning tablet computers.  If they send datasheet at least it can be confirmed that not the EJ898A is the problem.  

Its surprising that CHUWI seems to be not interested at all in this matter.  Maybe just normal for some percentage of chinese product to start burning so they can't understand all this fuzz....
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MrMkayMan| Post time 8-2-2017 09:07:28 | Show all posts
Hi, Thanks for the additional information.

Me as an embedded electronics engineer can't imagine that Chuwi or the supplier of the USB PD controller have overlooked at this issue. I think they tried to somehow solve it with a cheap trick. There is a possibility that on the tablet side there is something that will lower the voltage on this specific pin.
Do you have the schematic drawn out of the tablet side?
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artowi| Post time 8-2-2017 09:24:24 | Show all posts
One of my Hi13 is in use here and I don't want to open to check. The other one is at a repair center from CHUWI.
Probably no over voltage proection because nobody would expect a higher voltage on a signal pin.  
I don't see chances very high but maybe Etron will send me a datasheet for the EJ898A.

I think CHUWI just asked for a cheap USB-C power supply and expected it to be USB complient.  Soldering an USB-C connector to 12V is not the solution the developers of the Hi13 had expected....
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MrMkayMan| Post time 8-2-2017 09:51:13 | Show all posts
Edited by MrMkayMan at 8-3-2017 05:30
artowi replied at 8-2-2017 09:24
One of my Hi13 is in use here and I don't want to open to check. The other one is at a repair center ...

Lol, I don't expect you to open your device Big chance you can't see anything about it with small size electronics and multilayer PCB's.

But, a proper engineering approach is to verify and validate everything you get from manufacturers. Surely during design, but also with each batch a proper sample size needs to be inspected. If it really turns out the way you described, then things don't look too bright for all Chuwi Hi13's owners in the field. People leave there electronics charging over night, you know.. Something I always disapprove, even if it's a from a multi billion dollar company like Samsung.. oh wait..

update: Meanwhile I contacted Keyu about this issue. I hope they can give some clarification.
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mgeorgescu1990| Post time 8-8-2017 09:21:49 | Show all posts
Ok so, bad news, I bought the Aukey charger that was recommended, all good for almost two weeks, I charged the tablet with the original charger only two times. Now after almost two weeks the Aukey charger does not work. I also bought a new charger AND cable thinking that something is bad, and no, the new ones still can´t charge the tablet. So I have no other way just to charge the tablet with the original charger, I need the tablet for my studies. The original one charges it but the stories that you guys told me scare me. So yea, what happened ? What could have caused the issue? The tablet does not get hot on standby and the battery lifetime is decent. I have no USB C devices to test the port.
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ZenBalancer| Post time 8-9-2017 02:24:35 | Show all posts
Edited by ZenBalancer at 8-9-2017 11:36

Issues that might be linked to this thread:

Hi13 running hot and short batterylife.

Chuwi Hi13 USB C Blew up!! What should i do?

Edit: CHUWI Hi13 geting heated around USB-C /Edit.

This one is about the previous post of mgeorgescu1990 where the Emily account is missing the entire "spectrum of issues" in that thread and this thread the original charger is "being accused of":
Aukey recommended charger stopped working

Edit: correction + more threads.
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ZenBalancer| Post time 8-9-2017 02:29:41 | Show all posts
Edited by ZenBalancer at 8-9-2017 11:30

What do you all say to this advice from Chuwi to the bottom thread in my previous post? See:

emily replied at 8-9-2017 06:44
ok, could you please contact the service: service@chuwi.com and tell her you ant to buy a original charger, i think she will help you, have a good day


Edit: typo + quote completion.
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