About this replacement
Makita 4093D Series — 9.6V Ni-MH Replacement Battery (193889-4)
This is a 9.6V, 1500mAh Ni-MH replacement battery for the Makita 4093D cordless drill/driver and a wide range of compatible 9.6V Makita tools. It uses OEM part number 193889-4 and cross-references 9033, 9034, 191681-2, and several other Makita part numbers. Capacity is 1500mAh (14.4Wh), matching the original specification.
- 4093D and 9.6V platform compatibility: The 4093D shares its battery platform with the 4190DB, 4190DWD, 6095D, and 67+ other Makita 9.6V models. These tools use the same voltage rail, connector footprint, and contact arrangement — no adapter or modification needed.
- Bench tested on actual hardware: We ran this pack through a full charge-discharge cycle on a 9.6V Makita platform. The cells reached rated voltage without thermal event, and the pack seated and released from the tool body without resistance at the latch mechanism.
- Ni-MH break-in on first use: On first use, run the drill at half load — light drilling or driving — for two full cycles before applying maximum torque. Ni-MH cells need a few charge-discharge passes to stabilise internal resistance and deliver consistent current under motor inrush loads.
BMS overcurrent trip on trigger-pull inrush in the 4093D
The 4093D motor draws a sharp current spike the instant the trigger is pulled — this inrush can be three to five times the steady-state draw. On a new or cold Ni-MH pack, internal resistance is temporarily elevated, which pushes the voltage rail low at the moment of inrush. If the pack hasn't completed a break-in cycle, the protection circuit may read this sag as an overcurrent event and cut the pack out mid-trigger. Running two break-in cycles at partial load allows the cells to stabilise internal resistance before full torque applications.
Charger won't recognise a new pack after storage
Ni-MH packs self-discharge during storage — if a pack has been sitting for several months, cell voltage can drop below the charger's acceptance threshold, causing the charger to blink an error or simply do nothing. The fix is a manual trickle charge: use a compatible charger set to its lowest current output, or briefly connect a known-good pack to the charger first to warm the charge circuit, then swap to the new pack within seconds. Once the cells are above approximately 0.8V per cell (7.2V pack total), the charger will recognise the pack and begin a normal charge cycle. Do not force a fast charge on a deeply discharged Ni-MH pack.