Charger advice sought

Yes, generally not if it was solely for the FP2.
My thought when I do such a purchase is rather more general and multi-purpose also considering longevity. I think when going with FP this should always be taken into account.

BTW, minutes ago I tested with a 400 mA charger I have around home and it doesn’t trigger that mode on Lineage OS 14.1, :man_shrugging:

No, it isn’t. Fairphone has stated in one of the other charger threads that they did not make use of Qualcomms Quick Charge, although the SoC could do it. I have no official word on VOOC.

But even these are no “negotiation”. To my knowledge, “negotiation” only happens with USB 3 protocol. Without USB 3, the FP2 can’t do that.

So I have to asssume that the fact that FP2 will charge faster with certain adapters is only possible because of a spec violation. So it depends whether your adapter “thinks” you have a fast charging capable phone and therefore permits faster charging. Phones can signal this to the adapter by abusing the data wires, placing special voltages on them. But the FP2 won’t do that…

It is. Or rather, it was. Before the advent of USB 3, USB power got abused for lots of strange things. I have a USB coffee cup warmer here, as a gimmick.

At some point, PC manufacturers wanted to protect their motherboards with fuses. and chip fuses are the cheapest (because they can be placed on the PCB alongside all chips, resistors and capacitors. But chip fuses are hard to replace (actually needs lots of soldering skill…)

But when power to USB connectors became more sturdy and was no longer supplied by the communications chip directly (and possibly because of many repairs - we had some here where I work) they dropped the habit.

Ok, so I read deeper into the matter:

Unfortunately the article is rather confusing and does not clearly state what is actually in the USB spec (and in WHICH spec).

The most powerful mode PD (power delivery) to my knowledge is only on USB 3, and what Wikipedia calls BC (battery charge), signalled by 200 Ohms across both data lines to my knowledge is just “industry standard”, meaning it is not actually in the spec by the USB implementers’ forum.

Fairphone somewhere stated that they do not have the resistors across the data wires, so we would be stuck to 500 mA. If it takes more, than this is a spec Violation (only on USB 3 you are allowed to draw more).

Btw, maybe all of this will change, because the european commission is discussing the introduction of mandatory C type connectors (UBS 3.1) as common charging standard…

Maybe this term is not 100% correct in the way as simple devices interact with each other as between FP and any USB counterpart.
How would you call the mechanism when the charging current changes from ~500mA from a computer USB output up to ~1.4A with a wall-charger?
Maybe it is an USB2 spec violation, but if it´s not to be called “negotiation” what else is it called then? As USB2 spec violation is only the result of the process going on.

Hence it always charges with up to approx. ~1.4A on a simple charger if this can provide that much (even on my Yolk solar charger not having any power buffer) and the cable needs to have a proper wire gauge of course. The current is easy to be metered, e.g. the “Ampere” app does a good job as well.
Things change once there is a more sophisticated counterpart e.g. computer (charger with intelligence). Then the data lines come into account which are simply ignored (maybe not even connected) by simple chargers.
Depending on the voltage levels on the data lines defined by device specific resistor arrays the current is set (limited to ~500mA for FP2).

Unfortunately I´ve lost the link to someone at the xda-developer site who had a DIY all USB device charger. With it any phone (also apple) could be charged slow or fast as he was fed up with each device expecting its own type of charger to charge properly.
There was also a quite clear schematic available which showed the model specific resistor array that sets the current level as they are not all the same.

The battery charging spec you may find precisely here, a few PDF file with up to 72 pages.

Just as @AlbertJP has stated above.

I also was confused about these high currents as µUSB connector datasheets always show current limits for the connection pins which are much lower than what I could measure.

So as with µUSB which took several years to be commonly used, it again may take another ten years until it´s commonly used as the new standard.

Until then it would be nice to have regulations taking care of non-compliant USB-C cables respecting the specifications not frying any attached hardware as has happened to several customers out there in the past already.

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The USB device as being the power sink signals its demand. One method is the resistor across the data lines (+D und -D). The power source may adjust its power delivery, but it is not mandatory to do so.

Effectively it’s a mode switch. But negotiation would have to be two-way. Signalling to request a mode switch is unidirectional.


Yep, sounds feasible.
So I have one right here…

although it is manual :smile:

Called µconnect. For people who just want to charge (on the way) not needing/trusting a data connection.
It simply de-/connects the data lines to change the mode.

EDIT: µUSB magnetic add-on to any µUSB plug (white/black/purple iirc). Yes, works symmetrical with the magnet. Uses a somehow standard magnet also fitting with Goobays magnetic cable.
Yes, there can clearly be measured a current difference between the modes. But to be honest, I also have “standard” cables of not any special type which also gets the phone to charge with about ~1.4A (not on the computer). So it should not require this add-on to get FP2 to charge with its maximum current.

As I built my OTG adapter I also tried different resistors for this charging current issue but did not experience any difference here. Only with the data lines generally connected or not. The resistors I used did enable the OTG mode which in addition also uses pin 5 only available on the µUSB side.

Thank you. So this could be used to introduce the resistor that our FP2 lacks so that power supplies will mode sense a request for fast charge? What connector is that? Looks symmetrical, is this type C?

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I think it simply switches between the slow charge + data (500mA) mode and normal charge (max 1.5A) as the latter mode is activated when the charger (or out-of-spec cable) shorts the data lines, which prohibits data transfer.

My ThinkPad laptop activates 1.5A charging on one of its USB ports when it is in sleep mode - probably the same idea, shorting the data lines when no data transfer is required.

Thanks for this document. But:
“Notice: This agreement is not effective until a fully executed original has been received by the secretary at the USB Implementers Forum”. So we can take data from it , but it will have to be considered draft.

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That´s what I had at hand from the Wiki. It explained a lot for my needs. I do believe though that meanwhile there is something more up to date to be found somewhere else.

If it is not already in existence somewhere, maybe we should start collecting some measurement data?

I’ll start with a standard Blackberry charger, rated 850 mA, delivers 875 mA (measured). There is also a fast charger from Blackberry, haven’t measured that one yet. The 850 mA has the advantage of being ultra compact…

The fast charger from Blackberry is rated 1.3 A and delivers 1.47 A (measured). The voltage is slightly down (4.8 V compared to 4.97 V of the slower Blackberry charger), but this should not make any difference…

Standard charger from Samsung for the Wave II Phone (Bada OS): Rated 700 mA, actual output 762 mA.

Noname “TwinPower” car adapter (often used by marketing firms as giveaways with some manufacturers logo as an ad. This one having Kyocera branding, but is NOT built by Kyocera), that has two ports. A white labelled “smart” and “for Apple”, one black labelled “universal”. Total current rating is 3.1 A. Can be used simultaneously. Both (!) USB ports deliver 1.48 A (with nothing in the second port).

Standard Blackberry car charger (the old one with the attached spiral cord and micro-B USB connector), rated 500 mA. Measured output is 562 mA.

Fast Blackberry car charger (super compact, with 1 type A USB outlet), rated 1 A. Measured output is 1.14 A.

Related to post #15 by me which I couldn’t modify anymore:

I have found the pdf file about it, unfortunately only in German, but several links at the documents end leading to english sites and still some useful images and schematics are in.

usb-adapter-v12.pdf (429.8 KB)

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