[maemo-users] phone charger for N800 (was: kind of off-topic, but not completely: some questions about the N800)

From: Tim Ashman tim at ashmans.net
Date: Wed Apr 4 03:04:25 EEST 2007
I have been using the nokia phone charger first with my n770 and now with the 
n800 and have had no problems.  


On 04/03/2007 15:28, Paul Klapperich wrote:
> On 4/3/07, Eric Cooper <ecc at cmu.edu> wrote:
> > On Tue, Apr 03, 2007 at 01:33:10PM -0400, andrei raevsky wrote:
> > >  Just lemme know if I can use the same charger on my phone & N800
> > >  and I promise to get off your collective backs - at least for a
> > >  while
> >
> > Since the phone charger is rated for less current than the N800
> > requires, you would risk damaging the charger -- possibly overheating
> > or catching fire -- but probably not the tablet (unless it's consumed
> > in the same fire :-).  I'd recommend against it.
> Normally I would agree with this statement, but I'm not sure if I would in
> this case. Based on previous mailing list posts, it seems the N800
> essentially connects the charger port directly to the battery. Charging is
> basically controlled using pulse-width modulation--that is, the port is
> switched on and off with the percent on time and percent off time varied
> depending on amount of charge. This necessitates a current limited supply,
> as nothing is done to limit current in the device--equivalent resistance is
> equivalent to the battery internal resistance, which is going to be very
> small.
> Because the proposed power charger is of lower current, you're correct that
> the N800 won't be damaged by it. The battery will surely charge slower, but
> there shouldn't be any damage. I would be surprised to see any damage to
> the charger as well, though. It's true, the charger will be running at 100%
> current draw for much of the charge cycle, but this is true for any battery
> charger supply, and is definitely true for the charger built for the N800
> for the reasons explained above. It is possible that a PSU has inadequate
> cooling to hold it's max rated current draw indefinitely, but I find that
> highly unlikely for the charger built for the N800--and one would assume
> Nokia probably uses the same technique in their mobile phones, so I'd
> expect that to be unlikely of any Nokia charger.
> If you can find a charger that provides greater than the amount of
> > current required, it would be fine.
> No, this could be worse. Once the current is too high, the PWM will not be
> able to react fast enough and damage could occur. Generally, you're thought
> is a good rule of thumb, but not based on how this device is constructed.
> Ideally, an equivalent charger to the N800 would be best, but a lower
> current equal voltage supply should also be adequate.
> An unscientific test would be to charge your phone and your N800 both from
> a dead battery. If the charger gets noticeably hotter charging the N800,
> you probably don't want to do that again.
> On 4/3/07, andrei raevsky <raevsky.andrei at gmail.com> wrote:well, how abouyt
> > using the N800 charger on the phone, the other way around?
> If the phone uses the same method as the N800, charging the phone with the
> N800 charger might not be a good idea as it could damage the phone.
> I'd recommend you stick with the adapters meant for the units.
> --Paul

More information about the maemo-users mailing list