Robomow 12V Ni-MH Perimeter Switch Replacement Battery

Robomow perimeter switch new battery installed but mower still won't recognize the boundary wire

The perimeter switch uses its battery to broadcast a signal along the boundary wire — if the mower ignores the perimeter after a battery swap, the switch itself may not be powering on correctly due to a poor contact between the new cells and the terminal plate. Open the switch housing and check that the battery pack is seated firmly with no corrosion on the contacts. Ni-MH packs that have sat discharged for a long time can read a surface voltage that looks fine on a multimeter but collapse under load — charge the new pack fully before testing, then confirm the switch LED activates when powered. If the boundary light on the mower base station still doesn't respond, test the wire loop for continuity with a multimeter before assuming the battery is the fault.

Robomow perimeter switch battery drains completely between mowing sessions even when not in use

Ni-MH cells at this voltage class have higher self-discharge than lithium chemistries — a 12V Ni-MH pack can lose a meaningful portion of its charge over a week sitting idle, and the perimeter switch draws a small standby current the entire time it's connected to the wire loop. If the unit is losing charge faster than expected, check whether the switch is set to an always-on mode versus a scheduled operating window in the Robomow app or base station settings. We've seen packs in this form factor drop below the switch's minimum operating threshold after extended storage, which can cause the unit to appear dead even when it technically has residual charge — a full charge cycle usually recovers it. Put a multimeter on the battery terminals after a full charge and confirm you're seeing 13.2–14.4V before reassembling; anything below 12V at rest after charging indicates a weak cell.

Robomow perimeter switch keeps shutting off mid-session and base station shows boundary error

This typically points to voltage sag under the load of broadcasting the perimeter signal — the pack measures fine at rest but drops below the switch's cutoff threshold the moment it has to sustain output. Ni-MH packs degrade in this specific way: resting voltage looks acceptable but internal resistance has climbed enough that the pack can't hold voltage under even a light continuous draw. Check the resting voltage of your old pack; if it's above 12V but the switch still cuts out, internal resistance is the failure, not raw capacity, and a replacement pack resolves it. After fitting the new battery, run a full charge-discharge cycle before your first mowing session to condition the cells and confirm the boundary error clears.