Re: charging Time on the N9
 

Good post ototo, that is very informative. Is there a value in regulating charging speed? I've noticed that both my Pre 3 and iPhone4 (I get around it seems) will adjust and charge much faster if I plug them into the higher output wall adapter. The N9 is much pretty much constant no matter what. I'm assuming that allowing faster charging can be harmful to the lifespan of the battery, is that true?

Re: charging Time on the N9
 

It's a balance between the time needed to charge the battery and longevity of it's life. Besides that, depending on the current capacity and the level of discharge, different charging algorithm might be used.

AFAIK so called "rapid chargers" (those for standard batteries, e.g. AA, AAA) are using pulses of high current in some particular pattern to charge faster. I don't have any factual information on how that affects battery lifespan, but I'm pretty sure it comes with a price.

Same happens with N900 - charging from a computer (by connecting it to an USB port) is noticeably slower then charging from the "dedicated charger". The charging "machinery" there detects the type of the power source and adjusts algorithm.

Again, it's a question of balance.

I haven't checked if it charges faster with a dedicated "charger" comparing to charging from PC's USB port. It might be faster, as more current is available (same applies to special high current USB ports on some USB hubs/notebooks, which provide 1.2 A of current).

BTW, having an AMOLED display on board, device can consume quite a bit of the current provided by the power supply while charging. So, it should be possible to make charging a bit slower, if display will be on and showing some bright image (the brighter is the image, the more power display drains). Adding CPU load to that counts too.

Re: charging Time on the N9
 

Informative indeed.

However, it does not explain the following: if I use an iPad charger (5.1V, 2.1A) my N9 charges more slowly than with Nokia's own AC-16 (5.0V, 1.0A).

So there must be some sort of device identification/"compatibility" going on here. If that's the case, it is pretty annoying.

Re: charging Time on the N9
 

According to USB Battery Charging Specification v1.2, chapter 4.4.3:
where RDCP_DAT is defined in Table 5-3 Resistances as 200 Ohm max.

I have no idea what happens if that impedance is higher than that. If it's very high (e.g. unconnected pins) - the "charger" will not get detected at all (tried with cheap car USB charger).

So, I'd suggest you to measure impedance between two middle pins for both of your "chargers".

Re: charging Time on the N9
 

If the resistance between the data pins is over 200 Ohms, the device will not detect the chanrger as a high current source and therefore limit the current to 100mA. That the current it is allowed to draw from a PC USB port without requesting more power.
Since most wall chargers do not yet follow this new rule, they will only charge very slowly. This is the case with most wall chargers I tested. My solution was to use an USB extension cable and shorten the data wires. This doesn’t hurt at all, even you still would connect it to a computer.


Now, about the charging current:
I created my own external USB battery pack and did some measurement of the charge current. To my surprise, the charging current is highly dependant on the voltage supplied at the USB port. Since I wanted to protect my N900 and N950, I lowered the current to 4.1V. This made the current to go down to 300 mA max, even when the phone battery was completely empty. When I raised the voltage to 5.0V, I now can get 800 mA max. One could go up to 5.25V which is the maximum according to the USB specifications. Since I want to stay on the save side, I will stay at the 5.0V.
This will take maybe 1h for 70..80% and then slow down since the battery is almost full.


Beside of all, the charging electronics in the phone will limit the current. This means you can use any USB charger you have. How ever, if you supply a too high voltage (>5.25V), it might get damaged!

Re: charging Time on the N9
 

@caco3, @ototo

Great info, just finished modding car charger and USB extension cord for iPad charger and charge time on N9 dropped from 1444 minutes to 127!!!

Re: charging Time on the N9
 

Hi all,

Well I tried charging my N9 today with an Ipad charger, and got a message saying that there is not enough power to charge the device! :mad:

Has anyone else had this happen to them before? I live in the US, and thus the charger which shipped with the N9 does not work here.

How are you all charging your N9s apart from sticking it to a computer? Did you get one of those fancy world-plugs? Just a simple adaptor? What worked and what didn't?

Thanks
U_N

Re: charging Time on the N9
 

Whats written on the Ipad charger? All apple chargers I know provide at least 1A which is far enough.

Most likely it doesn’t work due the missing resistor between the data lines. see my post above...

Re: charging Time on the N9
 

I am charging my N9 with a Kindle's charger.

Re: charging Time on the N9