Battery power appeared on Nintendo handheld game consoles quite late - starting with Game Boy Advance SP. In the previous model - Game Boy Advance without SP - battery power. The author of Instructables under the nickname AndehX added a battery and a charge controller to this console, after which it became more convenient to use it. The backlight from this, however, did not appear, but the connector intended for connecting the PSU is standard, unlike the proprietary one on the SP model.
The master starts altering the console with reconnecting the battery compartment so that the elements in it are not connected in series, but in parallel. This is necessary, since now the device will be powered by two parallel LiFePO4 batteries, allowing you to immediately get a voltage of 3.2 V.
The wizard cuts a hole in the console housing under the Mini USB connector. Corresponding cords are still included with some card readers and displayless MP3 players. It’s better, of course, to install a Micro USB connector, then it will be much easier to purchase a cord.
The wizard takes a special charge controller for LiFePO4 batteries. The controller for Li-Ion- or LiPo-batteries is not suitable, since their voltage in the charged state is higher. The controller reduces the controller board while removing the USB connector, as it will be in a different place. At the same time, he makes sure not to cut any printed conductors on the board, except for those related to the connector. After refinement, the board is placed in the console housing. The master isolates it from the main board of the console; how it is not shown, but this must be done.
Observing the polarity, the master connects the Mini USB connector on a separate board to the input of the charge controller board, and with its output - the battery compartment, converted to parallel connection of the batteries.
He also places two LiFePO4 batteries in the compartment, observing the polarity, which must be pre-charged to the same voltage, otherwise when connected in parallel, one of them will start to discharge through the second. Closes the case. It recharges the batteries to rated voltage using the charge controller, after which the modified console can be used.
If the red LED blinks on the charge controller, this means that the batteries have about 5 minutes more energy left. It is urgent to save the game, if the cartridge supports this feature, and start charging the batteries.