About this replacement
Nintendo Game Boy Advance SP — 3.7V Li-ion Replacement Battery (SAM-SPRBP)
This is a 3.7V 900mAh Li-ion battery for the Nintendo Game Boy Advance SP (AGS-001 and GBA SP). It fits the original clamshell handheld console released in 2003. Compatible part numbers include SAM-SPRBP and AGS-003.
- AGS-001 and GBA SP compatibility: Both models use the same battery bay geometry, connector pinout, and charge management circuit. The SAM-SPRBP form factor — 55.16 x 31.71 x 5.44mm — seats correctly in either variant without modification.
- Bench tested on actual hardware: We cycled this cell on an AGS-001 unit and monitored the charge IC handshake. The BMS accepted the full 900mAh charge curve without fault flags, and the protection circuit tripped cleanly at low-voltage cutoff.
- First-cycle calibration on the SP: After installing this battery, run one complete play session to automatic cutoff before recharging. The Advance SP's fuel gauge IC sets its empty reference point against the first full discharge — skipping this step causes the charge indicator to read inaccurately for weeks.
Fuel gauge jumping or freezing after a battery swap
The Advance SP uses a basic coulomb-counting circuit to estimate charge state. When a new cell goes in, the IC has no baseline discharge curve for the new cell and starts counting from a stale reference. The gauge can show full charge, then jump to one bar without warning. One full discharge-to-cutoff cycle resets the reference and the gauge stabilises from that point forward.
Console not charging the replacement cell at full current
The SP's charge IC applies a conservative pre-charge current when it detects a cell starting below roughly 3.0V — this is a protection behaviour, not a fault. A new cell sitting in storage can arrive slightly below that threshold. Leave the console on charge uninterrupted for at least two hours on the first session. Once the cell crosses 3.0V, the IC steps up to full charge current and the orange charge light will hold steady rather than flickering.