Charging the NDS battery

The internal battery can be recharged about 500 times, which takes about 4 hours a time for a full charge. Nintendo warns that after those 500 recharges, battery life may have decreased to about 70% of its maximal potential.
We already knew that the AC adapter which comes with the Nintendo DS was compatible with the GBA SP: you can charge your GBA SP with the DS adapter. However, many people automatically assumed the opposite was also true: using the GBA SP adapter to charge your Nintendo DS. The manual doesn't explicitly deny or confirm this theory, but does throw in a warning to "ONLY use the included AC Adapter, Model No. NTR-002" (that's the Nintendo DS adapter).