LUBA charging stations: stuck or corroded contact pins block charging

The symptom

Two different owners hit the same underlying part failing for two different reasons, both presenting as a charging failure with the station otherwise showing normal lights:

Heat-deformed contact housing. The charging station's positive contact pin wasn't springing back out after the mower undocked on a LUBA 2 AWD X 5000X: visibly deformed plastic around the contact, "as if it had gotten warm." Freeing it with pliers restored charging immediately¹. The owner's dealer described this as a known, if uncommon, failure ("about 1 in 200 stations," per the dealer, not an official Mammotion figure, so treat it as anecdotal rather than confirmed). This pattern has reportedly also shown up in hotter climates internationally¹, a secondhand claim, not independently verified here.

Ant infestation. A LUBA 1-5000 owner's mower repeatedly backed out of the dock mid-charge, correcting its position and retrying until the battery died. After ruling out uneven ground (a shim under the front wheels fixed a separate, unrelated misalignment earlier in the same thread), the owner opened the station and found ants had nested inside: wet sand carried in by the ants had shorted the contacts². A replacement station and ant-repellent granulate around the base was the fix.

Contact film that a normal clean does not remove. A 2024 LUBA 2 5000 went into the same dock-and-retry loop: return to the station, announce charging, back out, retry three times, then sit there until the battery emptied, and still charged normally when pushed onto the dock by hand. Mammotion support read the owner's logs and told him the power supply was faulty, suggesting he order a replacement; the unit was out of warranty. Before buying one he measured 25.4 V at the pins with no load and cleaned both the pins and the plates with WD-40 and isopropyl alcohol, which helped only a little. A smart plug on the station's supply showed why: roughly 20 W drawn when the mower docked badly, against roughly 188 W once the connection was good. Buffing the pins and the contact plates with a metal-polish buffer (polishing rather than cleaning) restored a first-try dock and the fastest charge he had seen³. A second owner in the same thread reported the identical symptom and said a replacement power brick did not fix it, which is why this case is worth reading before accepting a "faulty supply" diagnosis.

A pin that is only sticking. An owner whose mower had started charging very slowly, or starting and then stopping, found the right-hand pin on the station "a bit sticky" and asked whether a lubricant was safe. Mammotion's own reply drew the line that matters: first work out whether the pin is simply sticking or the spring inside it is damaged, because "If it’s just sticking, you can try using a small amount of WD-40 to see if that helps. However, if the spring is damaged, lubricant is unlikely to resolve the issue."⁴ The owner reported a small amount freed the pin and the mower charged normally again, then cleaned the contacts with isopropyl alcohol⁴. Other owners in the same thread prefer a silicone spray or a contact grease instead; that is owner practice rather than Mammotion's advice. Mammotion's return-to-charge guide gives the check itself: press the pins gently, and they should move freely and spring back⁵.

No single cause confirmed. These are four distinct mechanisms (heat deformation, insect intrusion, a coating that survives a normal clean, and a pin that simply sticks) hitting the same physical component, not one firmware-linked defect. Three of the four were fixed at the station by hand (freeing a pin, polishing the contacts, a little lubricant on a sticking pin); one needed a replacement. Treat this as "the contact pins are a known weak point," not "there's one specific fix."