Hello
Sometimes I'm use the Nokia CA-146c Charger Adapter + Old Nokia charger:
ACP-12E
input: 100-240V~/50-60Hz/125mA
output: DC 5.7V /800mA

Adapter is very warming, is that right ? Can I use this old nokia charger (he's also a little warming) ?

Thanks

Have you used the new charger, and is it cooler? Chances are the n900 has higher power requirements and is pushing your old Nokia charger to its limits.

Do NOT use those adapters guys, there poor, they also came with the n97 and some melted (yes the adapter melted), take a read .. http://www.dani2xll.com/my_weblog/20...-meltdown.html

The pic was from a n97 user. theres other cases found on the net about it also.

Yep. Mine got so hot I stopped using it. I was trying to charge my N900 from a Power Monkey and concluded that I wasted more power in heat than I'd used charging the N900. Oh, and it was scarily hot

Edit: Come to think of it, I wonder how it can dissipate so much heat? It shouldn't need to be more than a bunch of wires and connectors, although I suppose it might need to be safe enough to cope with two chargers being plugged in simultaneously by the morbidly curious, so it may have some circuitry to deal with that.

It's warm, but not hot, nothing that seems electronics-threatening. I still use it at work with no issues. I use an original Nokia charger that came with my N80. The thin kind

@edit: Really? I expect to see a DC2DC converter, or some kind of SMPSU - thus the heat.

Though I'm guessing they went Chinese on us and used a LM7805. (The expression comes from the USB mug heater that had 3 LM78XX on the bottom). It's by far the easiest way to get 5V, stabilized, and it takes 6-12.

That would explain your heating issues. Older chargers have a higher voltage, especially when open-circuited and the LM dissipates the difference. You could always use a large wattage resistor in series. You DO have a soldering iron, right? :P

ndi's theory is very good -- I would also place my bets on the "charger" being a 115/230V. His theory would work if all the charger consists of is a 1:10 transformer, a rectifier (with capacitor), and then this LM7805. At 230V, we'd be feeding 23V to the LM7805; and at 115V, we'd be feeding 11.5V to the LM7805.

The thermal dissipation of one of these devices is 65 Cel./Watt (junction to air). While the designers of this charger believe it was sufficient for older model phones, we're talking about a smartphone with significantly higher power demands pushing this chip to its maximum current output.

Nowadays, chargers are probably made with a buck converter (takes higher DC voltages and steps it down) in light of new efficiency requirements.

OK...
I stopped using this charger and tried another one from N82:
AC-3e
input: 100-240V~/50-60Hz/100mA
output: DC 5.0V /350mA

I see the charging process on battery icon, Adapter not warming, but it's take a very long time for charging the battery...

I have tried two old chargers with the adapter. The AC 2X, with the old style round plug, made the adapter very warm and although the N900 showed it was charging it took forever and I have my doubts that it was charging at all.

I am now using an AC 5X, with the newer small pin charger from the N95, and the adapter does not get so warm and it charges a lot quicker. Although the dedicated microUSB charger is still the quickest by some way.

Charging from my laptop with the MicroUSB takes about the same time as the AC 5X.

this is stupid. couple incidents doesn't mean anyone should start spreading a panic.

and you should monitor your device anyway always when charging...

e: I have 4 adapters and I have used everyone. One has been a bit eaten by a dog, still works. Yes those heat but not too much.