Konecranes RMJ Crane Remote Replacement Battery 3.7V 1100mAh

Konecranes Mini Joystick Radio RMJ — 3.7V Li-ion Replacement Battery

This 3.7V, 1100mAh Li-ion cell replaces the factory battery in the Konecranes Mini Joystick Radio RMJ crane remote control. It restores power to wireless crane operation — lifting, lowering, and load positioning from the operator's position on the floor. Dimensions are 68.60 × 37.60 × 11.00mm; verify these against your existing cell before fitting.

• Mini Joystick Radio RMJ platform: The RMJ remote runs a single Li-ion cell to power the RF transmitter board, joystick inputs, and display. The BMS on this cell enforces a low-voltage cutoff around 2.5V — below that threshold, the remote will not power on even when a charged cell is inserted until the BMS re-initialises.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the bench, confirming the BMS handshake with the RMJ transmitter board. The cell held rated capacity within expected tolerance and passed overvoltage protection checks at 4.2V.
• Idle-period charging for infrequent crane use: If the remote sits unused for more than four weeks — common on standby cranes — charge the battery once monthly. Li-ion cells left discharged in storage can drop below 2.5V per cell, triggering BMS lockout that a standard charger cannot reverse.

Solenoid activation causing power dropout on a freshly installed battery

When an operator triggers a crane solenoid or relay through the RMJ, the brief inrush current spike can exceed what a low-capacity or partially discharged cell can deliver. The BMS interprets this draw as an over-current event and cuts output momentarily, dropping the remote off the RF link. This appears as a mid-operation freeze or reboot. Fitting a fully charged cell at rated capacity keeps the voltage rail stable enough to absorb the inrush without tripping the BMS threshold.

Remote showing low-battery indicator immediately after new cell install

Replacement Li-ion cells ship at storage voltage — typically 3.6–3.7V — not at full charge. The RMJ firmware reads this as a low-battery state and flags it on the display. This is not a fault with the cell. Connect the remote to its charger and bring the cell to 4.2V before first use; the indicator will clear once the remote reads full charge.