Vax BH15030 20V Cordless Vacuum Replacement Battery 3000mAh

Vax BH15030 / BH25040 — 20V Li-ion Replacement Battery

This is a 20V 3000mAh (60Wh) Li-ion battery that replaces Vax OEM parts BH15030 and BH25040. It fits Vax cordless vacuum cleaners that run on these packs. Voltage and cell count match the original spec exactly.

• BH15030 and BH25040 compatibility: Both OEM part numbers share the same 20V cell configuration, connector pinout, and BMS communication protocol. The vacuum's power management board treats this replacement pack the same as the factory unit — no resets or workarounds needed.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a Vax cordless vacuum test rig. The BMS held cell balancing across all discharge phases and the protection circuit tripped correctly at undervoltage before cells could be damaged.
• Dock charging discipline on Vax cordless vacuums: Do not leave the vacuum sitting on the charging dock continuously. Vax cordless models on permanent dock charge develop capacity fade faster than units charged only when the pack is depleted. Charge to full, then remove the vacuum from the dock.

Cordless vacuum losing suction before the battery indicator reaches low

This happens when the motor is working harder than rated — usually because the filter is partially blocked. A restricted filter forces the motor to draw more current, which pulls cell voltage down faster than normal. The BMS reads the voltage drop and reduces output to protect the cells, cutting available suction even while the indicator still shows charge. Clean or replace the filter first, then test suction again — a clear filter brings motor draw back to rated current and the full voltage headroom returns.

Motor cuts out mid-clean and then recovers after a few seconds

This is a BMS overcurrent trip, not a dead battery. When suction is restricted — by a blockage, a clogged filter, or heavy carpet pile — the motor draws a sustained current spike above the BMS threshold. The BMS cuts power to protect the cells, and after a short thermal or timer reset window, power restores. Clear any blockage, check the filter is clean, and verify the brush roll is free of hair wrap. If trips still occur on open flooring with a clean filter, check pack voltage resting at 20V before the next run.