Sharp EC-SR8-B Cordless Vacuum Replacement Battery BY-7SC17 25.2V

Sharp EC-SR8-B / EC-SR9-B Series — 25.2V Li-ion Replacement Battery (BY-7SC17)

This is a 25.2V, 1700mAh Li-ion replacement battery for the Sharp EC-SR8-B, EC-SR9-B, EC-HR7-T, EC-SR3SX-P, and related cordless stick vacuums. It replaces OEM part numbers BY-7SC17 and BY-7SA25. Fit the battery to the vacuum's pack slot and it powers the motor directly — no tools required.

• EC-SR8-B and EC-SR9-B platform compatibility: These models share the same 25.2V battery rail, physical connector, and BMS handshake protocol. One battery pack covers both, along with the EC-HR7-T and EC-SR3SX-P variants that run the same voltage architecture.
• Bench tested on actual hardware: We cycled this pack through sustained motor loads and monitored BMS response under restricted airflow conditions. The protection circuit tripped correctly at overcurrent thresholds and recovered cleanly once the load cleared — no latched fault states observed.
• Dock charging on Sharp stick vacuums: Do not leave this vacuum sitting on the charging dock permanently. Continuous trickle charge from the dock causes capacity fade significantly faster than charging only when depleted. Charge to full, then remove the vacuum from the dock.

Suction dropping before the battery indicator reaches low

On the EC-SR8-B, suction loss often precedes any low-battery warning by a wide margin. The motor draws more current when the filter is partially blocked, which pulls cell voltage down faster than the indicator circuit expects. The BMS reads this voltage sag as normal discharge and does not flag it as a fault — but available power to the motor drops noticeably. Clean or replace the filter first before assuming the battery is at fault.

Motor cuts out mid-clean and then restarts on its own

This is a BMS overcurrent trip, not a battery failure. When sustained airflow restriction forces the motor to draw above the pack's rated current limit, the protection circuit opens the discharge path. The vacuum stops, the BMS resets after a few seconds, and the motor restarts — then trips again if the restriction is still present. Clear the filter, check the brush roll for tangled debris, and confirm the dustbin is not overfilled. Once airflow is restored, the cut-out cycle stops.