The N900 does stop trying to charge if it notices it's not gaining ground when charging, apparently. Most of my testing have been with a hacked version of the charge21 script (I hacked out the setting of current and used it solely for monitoring charge current.) My (apparently) worn AC10C could not get past 400mA along with a lot of other cables (some can't get past 200-300mA) - and all of these that can't get past 500mA are not capable of allowing the N900 to boot when the battery is flat. That A1265 fake Apple charger has the same problem - I couldn't get over 400mA out of it.

I need to jury rig a good 5V bench supply that I can always hook up my phone to...