Weird charging question...

[lincpimp]

Ok, so I am pondering some things here...

I have a NIntendo DS (thanks Mike!) and I was wondering if I could use the charge port to power the unit from an external battery.

The wall charge outputs 5.2v dc at 450mah. The internal lipo is a 1000mah 3.7v lipo.

Now I have a few of the longer than a c cell - cells out of a laptop battery. I was wondering if I could parallel a few of them together and just feed into the charger port on the ds? The guy who I got the DS from already made a pigtail with a micro deans on it, but he suggested to remove the internal battery when using an external battery. S I am guessing this plug is hooked up parallel to the internal battery where it goes into the unit, and not at the charger port. The 5.2v must be regulated by a circuit to charge the internal battery, so can I use an external 1smulti-p lipo setup to power and charge the internal battery? I understand there will not be a cutoff, that is why the pigtail is attached where it is now as the internal circuits must cutoff the internal battery. Maybe I should just integrate the micro deans and make a switch of some sort to select which power source?

I just wondered if there would be any down sides to doing this? The external battery would only put in 4.2v at most, while the charger puts in 5.2v...

Any info would be handy. I am making up a case to hold everything and the laptop cells would fit nicely in one corner!