About this replacement
Worx WX373 Brushless Impact 20V MAX Drill — 16V Li-ion Replacement Battery (WA3527)
This is a 16V, 2000mAh (32Wh) Li-ion battery for the Worx Brushless Impact 20V MAX Drill. It fits the WX373, WX152, and related models that use the WA3527 or WA3539 battery pack. Slot it in where your original pack sits and you're back to full cordless operation.
- WX373 and WX152 platform fit: These models share the same 16V battery rail, slide-in connector, and BMS handshake protocol. The pack communicates cell state to the tool's motor controller, so the replacement must match the original voltage profile — this one does.
- Bench tested on actual hardware: We ran this pack through the WX373 charger cycle and monitored the BMS through charge termination. The protection circuit responded correctly to inrush current on trigger pull and held voltage within spec under sustained torque load.
- Motor-start conditioning on first use: On first use, run the drill at half load for two cycles before pushing maximum torque. This allows the BMS to log the motor's inrush current signature before it locks in overcurrent thresholds — reducing the chance of a nuisance trip on hard starts.
BMS cutoff on motor-start inrush during hard drilling
The WX373 brushless motor draws a sharp current spike the instant the trigger is pulled — especially when driving into dense material or using large-diameter bits. If the BMS hasn't profiled that inrush yet, it can read the spike as an overcurrent fault and cut power immediately. This isn't a defective battery. The protection circuit is doing its job. Running two lighter cycles first gives the BMS a baseline, so full-torque pulls no longer trip the threshold.
Charger blinking red on a new pack that's been in storage
Li-ion cells self-discharge during storage. If the pack drops below roughly 2.5V per cell, most chargers — including the Worx standard charger — will refuse to begin a charge cycle and signal a fault with a blinking red LED. The charger isn't broken and neither is the battery. To recover it, use a charger with a recovery or wake-up mode, or briefly apply a trickle current until cell voltage climbs above the 2.8V acceptance threshold. Once the pack is above that floor, the standard charger will take over and complete the cycle normally.