Does anyone use there N900 with a car charger?
I've been using my old 5800 charger that i brought from a major retail store, none genuine, with the adaptor that came with the n900.
However when using Sat Nav software and playing music through my car's HU (headphone jack into front aux), The phone actually uses more battery power than it can take from the charger. Is this normal or is it a problem with the charger?
The Mains charger than come with the phone charges it fine. I've also found that when charging from my pc at work using the data cable, it charges very slowly too.
Comes down to how much current the charger provides.
USB is only supposed to provide a 1/2 an amp though some manufacturers ignore this and provide more*. Most powered USB hubs also provide more.
I think the official N900 charger provides something like 1.5 amps and thus will charge 3 times faster than minimum-spec USB.
Likewise older chargers for less powerful phones most likely provide less current. It's specs are usually displayed on the charger between the pins.
Cheapo car chargers tend to particularly crap here, often providing the bare minimum needed to get a charging indicator on the phone they are designed for, which may well be woefully underspecced for an N900.
* and some device manufacturers also ignore this and require more. Anyone remember those godawful Alcatel SpeedFrog modems that wouldn't work with Via motherboards without the use of a powered USB hub? Those awful things needed about 0.68 amps in order to function.

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