About this replacement
Peterson SP-1 / StroboPLUS HD Series — 3.7V Li-Polymer Replacement Battery (YT603443)
This is a 3.7V 900mAh Li-Polymer cell replacing part number YT603443 in the Peterson SP-1, StroboPLUS HD, and StroboPLUS HDC. All three share the same battery footprint and connector. Swap it when the original pack no longer holds charge or the speaker cuts out early in a session.
- SP-1, StroboPLUS HD, and StroboPLUS HDC compatibility: These models run off the same 3.7V single-cell Li-Polymer architecture with an identical 43.70 × 33.50 × 6.00mm form factor and matching connector pinout, so one cell fits all three without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the SP-1 platform and confirmed the BMS accepted the pack without fault codes, balanced the cell correctly, and held the protection cutoff at the expected low-voltage threshold.
- Monthly discharge cycle for SP-1 users: If the SP-1 sits on a desk and gets topped off before dropping below 50%, run it down past 20% at least once a month before recharging — constant shallow cycling causes fuel gauge drift and accelerates capacity fade on the Li-Polymer cell.
Audio distorting before the battery indicator reaches empty on the SP-1
As the Li-Polymer cell discharges, internal resistance rises and voltage begins to sag under amplifier load. The amplifier hits its minimum operating voltage before the fuel gauge reads zero, so the audio clips and distorts while the indicator still shows charge remaining. This is a voltage-sag symptom, not a driver fault. A fresh cell with low internal resistance restores clean output — if distortion starts appearing above 3.5V under load, the pack has degraded past its useful point.
SP-1 not waking from USB charge after sitting unused for weeks
Li-Polymer cells left discharged for extended periods drop below the minimum acceptance voltage for USB-C PD negotiation — typically around 2.5V — and the charger handshake never completes. The speaker appears completely dead even with a cable plugged in. Some chargers will trickle-charge a deeply discharged pack back into range; plug into a 5V USB-A port rather than a USB-C PD source and leave it for 20–30 minutes before attempting a full charge cycle. If the cell has been in deep discharge for months, it may not recover.