N900 weird charging system
 

I have a couple of Bizpower battery packs, featuring 5V 1.5A output on an USB female connector (only VCC and GND pins). In the last months I used them to charge some portable devices (which had an USB plug for charging).

While it may sound strange, sometimes it has some sense charging a battery using another battery. For example - as in my case this week - when you are going to have a few days trip without any AC power plug all the way.

I just found that N900 does not start charging until some USB event happens.

That is, it doesn't charge when applying the CA101 USB cable to the above described "5V battery with USB plug".

And the N900 doesn't charge when applying the CA101 to my notebook in standby mode (while in standby mode, the notebooks keeps the USB power up, but the charging only starts when the notebook is running).

It only charges when there is some of its official cables/chargers.

This is quite annoying.

The quickest solution is to buy immediately another BL5J battery for the N900, and/or stop playing games, stop listening MP3s, stop watching videos, stop phone calls, stop browsing the network, stop, stop, stop... and crossing my fingers, hope to last three-four days.

Re: N900 weird charging system
 

The N900 will charge perfectly well with any dedicated charger which meets the USB charging specifications (i.e. has the data pins shorted). Unfortunately this seems to be a fairly recent change to the specifications, so a lot of dedicated chargers don't currently do this. I assume this is also why it won't work with your notebook in standby mode.

Re: N900 weird charging system
 

Yeah, basically the N900 want to negotiate a current with the charger. If the charger isn't made to do this, the Nokia refuses to charge. It could have assumed that any USB charger that doesn't support a negotiation protocol follows the USB standards. It doesn't.

The good news is, with a hacked cable adaptor you can probably use the battery solution you have now. As is the case with old "dumb" chargers.

More about it here: http://talk.maemo.org/showthread.php?t=38230

I also assume that this is the issue with the notebook - it can't negotiate while in standby.

Re: N900 weird charging system
 

Good: shorting D+ and D- works!

N900 follows "recent specifics" (expecting D+/D- shorted), while the BixPower Mobile Power Pack did only have a "dumb" setup.

I hacked a spare USB cable and shorted pins 2 and 3, triple-checked it, and finally saw my N900 battery charging from an external battery. Yay! :D

http://www.freeimagehosting.net/uplo...47a46fd5cc.jpg

Re: N900 weird charging system
 

Good stuffs!

I have my own opinions on which setup is "dumb" though. Sometimes simple really is better.

Re: N900 weird charging system
 

unfortunately common sense isn't very much appreciated sometimes when making these kind of standards...

Re: N900 weird charging system
 

Think with your dipstick Jimmy!