About this replacement
Crestron ST-1500 / STX-3500C Series — 4.8V Ni-MH Replacement Battery (ST-BP)
This is a 4.8V, 3500mAh Ni-MH battery pack replacing OEM part ST-BP. It fits the Crestron ST-1500, ST-1550C, STX-1600, and STX-3500C wireless remotes — the handheld controllers used to manage Crestron home automation and AV systems. Voltage and cell count match the original pack exactly.
- ST-1500 / STX series shared battery platform: These four models run the same 4.8V four-cell Ni-MH pack with the same connector and physical footprint. Crestron standardised the battery format across this controller generation, so one part number covers all four remotes listed.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on a ST-1500 unit and confirmed the battery charges to full capacity without the remote flagging a low-battery condition prematurely. IR output held consistent across the full discharge curve.
- Multi-cell pack replacement rule: This is a sealed four-cell pack — install it as a complete unit and do not attempt to replace individual cells inside it. Splitting the pack voids the cell balance and causes uneven discharge between cells, which shortens total pack life faster than normal cycling would.
Why the ST-1500 stops responding mid-session on a partially charged pack
Ni-MH cells have a steeper voltage drop near the end of discharge than alkaline cells do. The ST-1500 draws a short, high-current burst every time it fires an IR command. When the pack voltage dips below roughly 4.2V under that burst load, the remote's controller can reset or drop the transmission entirely — even if the battery indicator hasn't flagged low yet. This is a load-response issue, not a firmware fault. Swapping to a fresh pack resolves it immediately.
ST-1500 shows full charge but IR range drops noticeably
Ni-MH packs that have been shallow-cycled over many months develop reduced capacity through a process called voltage depression — the pack measures near-full but can't sustain the current the IR LEDs need at distance. The remote works up close because the receiver is more forgiving at short range, but the LED output is still below its rated drive level. A full discharge-recharge cycle on the new pack will recondition the cells and restore normal output. Charge the ST-BP pack fully before first use to establish a clean capacity baseline.