About this replacement
Shimpo DT-315A Series — 9.6V Ni-MH Replacement Battery (BAT-DT315AP-ASSY)
This 9.6V 3000mAh Ni-MH pack replaces the original battery in the Shimpo DT-315A digital tachometer and DT-315A Stroboscope. It matches the OEM voltage rail and connector footprint used across both instruments. Capacity is taken directly from product data — 3000mAh, 28.8Wh.
- DT-315A and DT-315A Stroboscope compatibility: Both instruments share the same 9.6V battery bay, connector pinout, and BMS handshake protocol — the stroboscope variant draws higher peak current during flash events, but both operate within the discharge curve this cell chemistry supports.
- Bench tested on actual hardware: We cycled this pack through the DT-315A's power-on sequence and stroboscope flash load. The BMS held without tripping on the initialisation spike, and the cell voltage recovered cleanly to float between measurement bursts.
- Post-install calibration cycle: After fitting this pack, run a full calibration cycle through the instrument menu before field deployment. The DT-315A maps battery state during calibration — skipping this step causes premature low-battery warnings on the first measurement session, even with a fully charged pack.
BMS lockout after the DT-315A sat unused in a carry case for months
Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A pack stored for three or more months can drop below the BMS recovery threshold — typically around 8.5V for a 9.6V eight-cell Ni-MH stack. When the instrument reads this voltage on power-on, it refuses to boot and shows no display activity. To recover, place the pack on a dedicated Ni-MH charger set to a low trickle rate (0.1C) and allow it to charge for 12–16 hours before reinserting. Once the pack clears 9.0V, the DT-315A's BMS reinitialises normally.
RPM readings resetting or dropping out mid-logging session
This is not a sensor fault — it is a sustained-load voltage dropout. The DT-315A's optical sensor and display draw continuous current during a logging session, and a partially degraded cell in the pack will sag below the instrument's minimum operating voltage under that load. The instrument interprets this as a power interruption and resets the active log. Check resting voltage before a session — it should read at or above 9.6V. If the pack rests at full voltage but still drops out under load, the internal resistance of the old cells has climbed too high and the pack needs replacement.