i had the same orange flashinng led issue too few weeks ago and solved it by charging my battery with 5800 for 15minutes. the battery was simply too empty to get even the charging mde booted

I had a similar problem, bright orange LED flash on a dead N900 followed by weak red flashes when plugged in.
I wiggled the battery contacts with a safety pin and reinserted the battery, started with about 60 seconds of steady orange LED then the normal pulsing orange.
<few minutes later>
I can now boot up, must have done something when frequently switching between a prepaid sim and the sim from my laptop modem.
I will still need to replace the fall damaged microUSB port to make charging reliable, it requires being set on a book with the cable drooping a bit to charge.

Still having charging issues, sometimes I can boot sometimes I just get the weak red LED flashes. If the USB port is wonky will it show charging when the phone is on or off when the data pins are connected but ground or power are not?

Flashes are the battery charge chip signaling error.

Just connecting d+ d- together doesn't make bme think charging is happening..

However, having all pins properly connected and then disconnecting gnd or +5V might make the charger chip immediately stop charging, but enough voltage to remain for several minutes to make bme think there's external power available.

Shadowjk,
Then I hope that the replacement USB port when it arrives and is installed will work better. The stock USB port on my used N900 has always been a little wonky and required perfect positioning to get it to charge.
I have finally been able to get host mode working withing the last few days since I repaired the broken USB port and I was worried that this may have started when I had host mode running and added auxiliary power form my laptop USB port to power a portable hard disk.

Hi shadowjk

Do you have more experience with this short orange flashes?
I am building my own external battery with a small DC-DC converter, making 5V out of 2x 3.7V Li-ion cells.
When I put my N900 on, I get 2 or 3 short orange flashes. The phone sais its getting charged, but no current flows. Having a look on my oscilloscope shows that my 5V are steady (as designed), but every time the orange light flashes I can see a power surge ( <2ms) and the voltage drops quickly down to 4.1V. This could be just due the needed power for the LED or it could also be the "intelligence" of the bme.

Any clue how to get it charging despite of that?
My dc-dc converter can supply 5.0V constantly with a load up to 1A, so that cant be an issue.

Yeah at 4.1 it's probably flashing for "Undervoltage" error.
A led wouldn't use much power.

Try add capacitors on your output as close to N900 as possible?

I myself built a pack out of a 11.1V rc lipo battery and a 5V/3A RC UBEC, and that seems to work.

I tried to solve it with adding enough capacity to the output voltage, wasn't happy with the needed physical space. I I was controlling the PWM with an microcontroller, the voltage controlling is quite slow (ADC needs time). So I am now going to try it with an MC34063 IC, that should work.

Did you ever calculate the efficiency of your DC-DC converter? How big is it?

The one I used: http://www.hobbyking.com/hobbyking/s...idProduct=3735

The phone charging was a secondary feature. I have two of those powering heated gloves, and one of them also has a usb port for my n900 :-)