About this replacement
Makita 4093D Series — 9.6V Ni-MH Replacement Battery (193889-4)
This is a 9.6V, 3000mAh Ni-MH battery for the Makita 4093D cordless drill/driver and a wide range of compatible Makita 9.6V tools including the 4190DB, 4190DWD, and 6095D. It matches the OEM voltage rail and physical connector of the original 193889-4 pack. Capacity is rated at 3000mAh (28.8Wh).
- Makita 9.6V platform compatibility: These models share the same battery bay geometry, contact layout, and 9.6V nominal rail. The BMS in each tool communicates discharge state through the same two-contact interface, so one pack spans the full 9.6V lineup without modification.
- Bench tested on actual hardware: We cycled this pack on a 4093D under repeated trigger pulls and sustained drilling loads. The BMS held discharge cutoff at 8.4V and returned stable voltage recovery between cycles with no unexpected thermal interruptions.
- Motor inrush conditioning on first use: On first use, run the drill at half load for two cycles before applying full torque. This lets the BMS profile the motor's inrush current draw and calibrate overcurrent thresholds before you hit maximum load applications.
BMS cutoff on drill motor-start inrush surge
When you pull the trigger on a Makita 4093D, the motor draws a spike of current well above its running draw — often three to five times higher in the first milliseconds. On a new or cold pack, the BMS may read this spike as an overcurrent fault and cut the circuit before the motor even starts turning. Ni-MH cells are more tolerant of inrush than Li-ion, but a fully discharged or cold pack still raises internal resistance enough to amplify the voltage drop at that spike. If this happens, let the pack rest for two minutes at room temperature and retry at a lighter load setting first.
Tool bogs under load mid-drill and loses torque
If the drill starts strong but loses power and bogs halfway through a fastener or hole, the cause is usually voltage sag — the cell voltage drops under sustained current draw faster than the tool's regulator can compensate. On Ni-MH packs, this often signals either high contact resistance at the battery terminals or cells that have been repeatedly shallow-cycled and lost capacity. Clean the battery contacts on both the pack and the tool with isopropyl alcohol and check for oxidation or debris. If sag persists after cleaning, measure open-circuit voltage — a healthy fully charged 9.6V Ni-MH pack should read between 10.5V and 11.0V at rest.