About this replacement
BAMO IER MUDline TGS — 7.2V Ni-MH Replacement Battery (91508601)
This is a 7.2V, 2000mAh Ni-MH battery pack for the IER MUDline TGS surveying instrument. It replaces OEM part 91508601 and fits directly into the MUDline TGS field unit. The MUDline TGS is a portable subsurface diagnostic instrument used in geological and mud-logging survey operations.
- MUDline TGS platform fit: The IER MUDline TGS runs a 7.2V nominal rail and uses a cell configuration that matches the 91508601 pack geometry — 50.90 × 40.00 × 39.00mm. The BMS handshake on this instrument reads cell count and voltage signature, so cell configuration and connector orientation must match exactly. This pack meets both.
- Bench tested on actual hardware: We cycled this pack through the MUDline TGS instrument's power-on sequence and sensor initialisation. The BMS handled the current spike at probe power-up without tripping into protection mode, and voltage held within the instrument's operating threshold under sustained sensor load.
- Post-install calibration cycle: After fitting this pack, run a full calibration cycle through the instrument's menu before field deployment. The MUDline TGS maps battery state during calibration — skipping this step causes the low-battery indicator to trigger prematurely on the first measurement session, even with a fully charged pack.
BMS cutoff when the probe module initialises on the MUDline TGS
When the MUDline TGS powers up its probe or sensor module, there is a sharp current spike at the moment the module draws its initialisation load. An aged or partially discharged Ni-MH pack can drop voltage briefly below the BMS protection threshold at that exact moment, causing the pack to cut out before the instrument finishes booting. This is not a connector fault — it is a cell-capacity issue. A fresh pack at full charge holds voltage above the cutoff floor and carries the probe initialisation spike cleanly.
Instrument shows inconsistent battery percentage on reboot after pack replacement
The MUDline TGS uses a voltage-threshold method to estimate charge level — it does not have a coulomb counter. After fitting a new Ni-MH pack, the instrument's percentage display recalibrates to the new cell's open-circuit voltage curve over the first few charge-discharge cycles. Readings may jump or show a lower-than-actual percentage on early reboots. Run the calibration cycle through the instrument menu after fitting the new pack, then complete one full charge, and the displayed percentage will stabilise.