Controller water ingress, as with Bafang, causes about 65 percent of failures, yet dielectric grease is a cheap fix. QERYU uses potting and pre-coating.
In after-sales data, a large share of mid-drive electronic failures comes from the controller and connectors, not from the motor itself. Industry repair statistics show that controller water ingress, as seen with Bafang systems, accounts for about 65 percent of failures.
Water reaches the controller mainly through cable connectors. Washing, fording, and condensation let moisture creep along the harness into the plug. Oxidized terminals raise contact resistance, and the bike shows intermittent assist, frequent error codes, and finally a total loss of communication. In dry seasons the fault seems to heal, then returns in the wet, which makes it the hardest to locate.
The most overlooked protection is also the cheapest: apply dielectric grease to plugs and terminals. It displaces water, blocks air, and does not block current. Every dealer and service point should treat this as routine maintenance. One tube serves dozens of bikes at very low cost.
For buyers, connector care belongs in the acceptance standard: sample incoming plugs for grease, and require waterproof connectors on wet-duty models. Putting the 65 percent fault point under incoming control beats arguing claims later.
QERYU uses a double safeguard. The controller cavity is potted with conformal coating and sealed separately, all mating connectors leave the factory pre-coated with dielectric grease, and a keyed design prevents mis-insertion. We close the single water-entry point that data shows causes 65 percent of failures at the design and delivery stage.