TEK AK77 Compatible Battery 21.6V 2000mAh Li-ion LPB-05

TEK AK77 / AK80 Series — 21.6V Li-ion Replacement Battery (LPB-05)

This is a 21.6V, 2000mAh (43.2Wh) lithium-ion battery pack for TEK cordless stick and handheld vacuums. It fits the AK77, AK80, A6, and A7 models. OEM part numbers covered: LPB-05, A09-01, and ZB1758-6S1P-01.

• AK77, AK80, A6, and A7 compatibility: These four models share the same 21.6V rail, connector housing, and BMS handshake protocol. Swapping between them requires no adapter — the pack seats and communicates identically across the series.
• Bench tested on actual hardware: We ran this pack through the AK77 motor circuit under simulated blockage loads. The BMS held steady through normal draw and tripped correctly on sustained overcurrent — no false cutoffs during standard use.
• Dock charging on cordless vacuums: Do not leave the vacuum on the charging dock permanently. TEK stick vacuums on continuous dock charge develop capacity fade faster than units charged only when depleted. Charge to full, then remove from the dock.

Suction dropping before the battery indicator reaches low

This happens when the motor draws more current than the BMS considers safe under load — not because the cell is empty. A partially blocked filter forces the motor to work harder, pulling sustained high current that causes voltage sag at the cell level. The vacuum loses suction noticeably while the indicator still shows two bars. Clear the filter and check for blockages in the brush head before concluding the battery is at fault.

Motor cutting out mid-clean and recovering after a few seconds

This is a BMS overcurrent trip, not a dead battery. When airflow is restricted — blocked filter, tangled brush roll, or a sealed nozzle — the motor draws a sustained current spike the BMS flags as a fault condition. The pack shuts output, cools briefly, then resets. The fix is airflow, not the battery: clean the filter, clear the brush roll, and confirm nothing is sealing the nozzle before the next run.