PC Engine GT Rechargable battery options

[kamiboy]

Let's face it, 6 batteries is two too many. Most rechargable AA battery chargers fit only 4 at a time, so you would need two rounds to recharge 6, and it takes forever. Besides, most chargers are not exactly compact, which reduces the overall portability of the system.

So I got to thinking, perhaps I can forego AA batteries for one modern device battery. There is plenty of room inside the GT battery compartement.

Things to consider:

Which battery pack to go with? There are many factors to consider, but chiefly it must be small enough to fit inside the GT battery compartement, but large enough to provide as many mAh as possible.

What output voltage would I need? The GT wall adapter is rated at 7 Volts, which corresponds well with 6 x 1,2 Volts adding up to 7,2 volts.

How to charge the battery pack? I want an elegant solution for this. Best case scenario, It can be hooked directly to a USB power source. Alternatively, charged with a very compact dedicated charger.