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#21
Originally Posted by woody14619 View Post
Speaking of huge... Mind the size of the pad. Some are wider than the N900. Consider orientation and dimensions when making your selection as well.
The dimensions of the one i posted seems perfect
 
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#22
Originally Posted by pichlo View Post
Thanks Woody, that's exactly where I was heading with that question. I would not expect to connect the receiver's contacts directly to the battery contacts. But, assuming some magic circuit between the two, would the phone's firmware be able to cope with it? Reporting the correct charge, for example?
Looking at one of the links above it has been done.
If it is putting strain on the charging circuitry inside the device it yet to be proven.
It seems the battery charges without the device knowing about it. I would assume shorting the Data pins would trick the device into thinking it's charging.
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#23
Originally Posted by sixwheeledbeast View Post
Looking at one of the links above it has been done.
If it is putting strain on the charging circuitry inside the device it yet to be proven.
It seems the battery charges without the device knowing about it. I would assume shorting the Data pins would trick the device into thinking it's charging.
Shorting data pins makes the N900 able to charge as normal from 5v run through the ground and USB 5v+ pads.

If you have a Li-ion charge board to add to your phone that charge logic will handle the required 4.1v charging voltage and terminating charge for a full battery on your 3.7v BL-5J battery, it takes a reboot in my experience to get the N900 to report correct charge state once you are finished charging.using an auxiliary charge manager circuit.
 
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#24
I'd say Qi is far more prevalent today that Touchstone. You can find Qi based items all over the place. In fact, there are apparently 3 separate charging systems out in the wild, though until to day I'd only heard of one. Guess which one is winning... Short of Apple grabbing one of the lesser specs (or inventing their own) Qi seems to have the foothold.

Most devices have Qi built in, or (if smart) have connectors under the back cover, and a slim insert or cheap back-plate with the receiver. That would allow them to simple replace that insert or back with another standard receiver if the tables get turned somehow. Right now though, that market looks to be 100% Qi based. (Samsumg, LG, Qualcomm and Nokia are all behind it... so there's a reason it's winning.)

The "best" way to do this with the N900 as is today would probably be a pass-through system. The power on the receiver would switch the external USB pins off (via relay or transistor) and connect on in a way that make it look like a charger of proper amperage. That allows the device to continue to know about charging in the way it's used to, eliminates port wear, and doesn't require a software re-write.

Doing that in form factor for the N900 would be tough. But if the Neo900 were to have that built-in with exposed pins for power-in from such a plate? May be a last minute request to throw in there?
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#25
Hola comrades, I've been requested to post whats below. I hope it helps:

Originally Posted by Estel
Having current bypass USB +5V/USB ground pads mean that you will never get values measured correctly by bq27x00_battery module. Current must pass through charging chip, data pins shorted or not.

Again, shorting data pins by opto or whatsnot is not necessary if you use Pali's BME replacement (no reasons why you shouldn't). Just use the echo'ing thing everytime you want dedicated charging. Also, you can just wire charger to USB +5V/ground pads under battery, it *will* make current go through charger, and bq27x00_battery will get calibrated.

BTW, there is no real-life risk while using pads under battery, unlike what joerg said. They lack common-mode-choke and some external rudimentary second defense line as opposed to going through normal N900's microUSB port, but charging and USB chip still have it's build-in protection, rated few kV (seven, if memory serve... Or was it eleven? Anyway, much more than you will ever need). AFAIK, robbiethe1st uses this method for years, since his USB port died beyond repair, without any problems. I use it too, for two devices, in very EMI-dangerous places, without any special cables/additional shielding, and it works just fine. No reasons, why it shouldn't, BTW, if you check datasheet of USB and charging chip, noting it's internal protection(s).

Woody's trick with opto's was necessary during times of Nokia's BME, but now, he is obsolete.
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Last edited by backcover_press_service; 2014-06-05 at 21:40.
 
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#26
Originally Posted by backcover_press_service View Post
Hola comrades, I've been requested to post whats below. I hope it helps:
Glad to see Estel is taking the ban policy seriously, as always.

Honestly, yes, opto's are almost always overkill, but they're a risk reduction tool. Which would you rather do if a static charge hits your device just right? Replace a 50 part designed to take the hit, or lose your N900? It's your device, and your decision to make based on your opinion.

You know what they say: Opinions are like Estels. Every forum has one, and they all are usually banned.
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#27
FWIW I have also ordered a Qi universal charger just to see, It looks to protect the USB port from dust as well as being easy to remove for host mode or mass storage. I will post in a thread, maybe not here though, my results when it arrives.
 

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#28
I posted the steps to get the Qi universal receiver to work with the N900 and charge properly: http://talk.maemo.org/showthread.php...01#post1431701
No mods to phone required beyond a bit of electrical tape, some soldering required as the Qi charge receiver linked at the top of the thread does not have shorted data pins required by the N900 battery charging circuit.

Last edited by biketool; 2014-07-03 at 09:28.
 
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#29
As I am looking for Qi chargers atm I ran into this http://katalog.we-online.de/en/pbs/W...5#vs_t1:2_ct:1

can be ordered at rs-online.com (be aware that the older rather thick coils are also available but might not fit a phone I hit the search with the first digits of the WE productcode)
 
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#30
My final install was to stick the charge receiver onto the back of my Mugen battery cover, with a double Scud battery there is just not enough room.
I would love to find some sort of elastic super sticky membrane to stick this to the outside of my cover as it looks rather junky with electrical tape.
I suppose it is pretty cyberpunk-now though, badass pocket computer phone, shabby post-apocalyptic exterior.
Qi is pretty cool, I really like it and how my port is now well protected at all time unless I am doing USB host mode.
 

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