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ChuwiHI13 and the Keyu battery charger

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szucsi|Post time:12-6-2017 16:16:59 View:1311|Reply:69

MemberChuwi| Post time 10-28-2017 04:53:09 | Show all posts
Edited by MemberChuwi at 10-28-2017 06:42

Tried to check out the 'oxidation' theory.

Here you find a typical plug you can order at Conrad Electronics - and a related spec Sheet. ... t-1-st-1395591.html

Contact material used is a copper alloy. Typical contact resistance is 40mOhms (=0,04 Ohms) new and 50mOhms (=0,05 Ohms) after some typical use. This is less than 1% compared to the discussed load resistance of 6 Ohms with Hi13 and therefore irrelevant. Even if wearing is assumed to be much higher, maybe 0,5 Ohms it's still less than 10% in the chain and still not a major problem.

Nominal voltage is 5V. So you could claim something to be out of spec. But that's just nominal. Insulation has been rated for 100V, so 12V isn't a severe issue imho. It does no harm or wear the contact additionally, especially if you plug in before you power the charger. This is what I prefer doing.

Temperature is speced up to 85℃. Usually you can't touch a surface for long that is 60+℃ . That's a pretty simple method to get an impression of temperature. If you can touch permanently it's below 60℃. Never experienced that limit with my Hi13.
What about contact power dissipation? It's approximately 160mW in typical case. Even a small resistor can dissipate this without heatsink. But we are talking copper contacts and metal wires that can transport and dissipate this bit of heating power for sure without any trouble.

Remains the current spec to be unclear. The mailorder claims 1.25A... not sure what that means. If it's per contact then we are in the 5A zone (4 contacts Vbus and Gnd each) which is more than enough for Hi13 needs.

All this data renders the heat/oxidation/wear theorie in real life to be very improbable. Guess high quality plugs have gold coated contacts, not just copper alloy, and will perform even better.

I can't find any point that speaks for the oxidation theory - except general aging. But that applies anyways, regardless if you use a device or not.

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MemberChuwi| Post time 10-28-2017 06:41:30 | Show all posts
For completeness a typical device connector ... f=Product%20Details

Similar specsheet. Indeed 4x1.25A = 5A total. This means even two contact pairs would be sufficient to charge Hi13... no bottleneck.
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szucsi| Post time 10-30-2017 06:43:39 | Show all posts
Edited by szucsi at 10-30-2017 06:47

This is true, but you have to look at Hi 13 after a couple of months of use, the gold coating is completely worn out. (because it is too thin and needs to be filled with relatively small scales because of the high battery usage). And then the trouble starts. You do not see this outside, nor how much dust is added to the contacts.It's a pity that the Hi13 motherboard manufacturer does not buy parts from Conrad.
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MemberChuwi| Post time 10-30-2017 07:47:46 | Show all posts
The referred connectors material with Conrads examples is copper alloy. That's nothing special. If Chuwi uses a connector that has any gold coating it is better from start.

Dust can be removed with a fine brush, that's not a big deal imho. You can add a very tiny bit contact spray onto the brush bristles if you feel a need for maintenance and reduced abrasion.

Your observation looks more like mechanical wear than an electrical issue. Do I understand right that your trouble is bad charging performance? Probably an old style charging only connector would have been indeed a better choice than USB-C.

The more I think about USB-C the less I find it any good. Especially Gen 1 is nothing else but UBC 3 functionallity with a stupid plug adding dangerous charging...   
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szucsi| Post time 10-31-2017 12:29:56 | Show all posts
MemberChuwi replied at 10-28-2017 00:10
To be honest, l don't trust speculations with PD communication as long as I can't see a sniffer prot ...
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szucsi| Post time 10-31-2017 12:34:09 | Show all posts
Edited by szucsi at 10-31-2017 12:39

This image is made of a 3-month Keyu charger connector. Well, if we do, if the oxidation is done and the tablet is ruined.   

Keyu usb-c plug

Keyu usb-c plug
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MemberChuwi| Post time 10-31-2017 13:06:49 | Show all posts
Oh, that's a misunderstanding. I have seen this already. We don't need to discuss this again. Keyu is crap and this plug too.

No, I was about 3rd party chargers, why some work and others not and the USB-C connector in the Hi13 tablet itself.
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MemberChuwi| Post time 11-2-2017 21:51:21 | Show all posts
My latest suspicion is that Hi13 charges faster with a PD charger. I have that impression. Can anybody confirm this?

It would also explain why 24W chargers and batteries not able to provide 3A @12V don't work with my tablet.
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szucsi| Post time 12-5-2017 18:16:52 | Show all posts
Edited by szucsi at 12-5-2017 18:19

24 watt charger is not enough for the Hi13 battery. Requires at least 45 watts of power. P = U × I
12x3= 36
So there must be a minimum of 36 Watts charger to provide 3 amperes charging current. But since while the tablet's power is at least 15 watts, the 45Watt charger is minimum recommended. But 50-60W power would be the most optimal, with a PD charger.
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MemberChuwi| Post time 12-6-2017 16:16:59 | Show all posts
Edited by MemberChuwi at 12-6-2017 17:01

I'm not sure where your numbers are coming from. 3A need? 45W? 36W? 15W?
If you were right the keyu charger couldn't charge either as it's 12V / 2A or 24W only. But it does.

More than 3A seems to be unlikeky too because that needs a dedicated cable actively confirming to be compatible with this. But 3A current is no need defined by the cable, just a requirement a standard USB-C cable should stand, less is ok too.

Sorry, to me it's a mess what you say here.

You know a formula but the point is to put that in a logical perspektive.

Let's asume Hi13 requests 3A but uses just 2A like the keyu provides. A PD charger can not know about this and a 24W charger must refuse a 36W request. That's a negotiation issue then, no power need issue. PD is not as simple as you try to put it.
I think all analysis has already being done. Missing is just a proof what really happens - which needs PD lab equipment.

It can't be decided with a formua because we deal wiith three communicating devices, hi13, active cables and a communicating charger, and any or all can be buggy too. It's not a plain matter of physics.

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