I own an Ocean Current with the 48v 17.5Ah battery, had this bike for the last 20 months and covered 8000km so far, just recreational cycling covering a 100km or so a week, battery is rarely removed from the frame and is charged on the bike.
Over the last month I have had intermittent drop outs with the torque sensor, I checked all the wires and plugs for damage, nothing, also I get a real humming from the motor under load, vibrates right through the frame, I took the back wheel off to replace the chain and cassette as the chain as getting quite worn, took the opportunity to open the motor, all pretty clean, no water ingress, the nylon planetary gears look fine, barely any wear, I have to say the humming is from the straight cut gears with a little bit of wear, added a touch more grease and reassembled the motor, didn't make that much difference.
Last week the battery dropped to one flashing led on the battery meter, I turned the bike off, turned it back on and seems to work ok, get home but the range has dropped.
When I first had the bike I could do 45km before the battery meter drops to 4leds, then twelve months later the range drops to 35km before it drops to 4leds, now it was only getting to 25km,
I could still do 50-55km which is drop from the 75-80km when new, but I do expect some range loss as the battery ages.
So anyway, get home and remove the battery so I can check the power socket, the female socket was full of dust, blew this out with compressed air then cleaned the sockets with alcohol and micro brushes, scraped a bit of corrosion out and tightened the sockets a bit, each socket is four segments of a quarter circle, very carefully bent these in with a fine screwdriver, then I took the locking plate out of the bike and cleaned the pins with autosol polish and thoroughly cleaned with alcohol and compressed air.
Put it all back together and fitted the battery back on, I also put a wide stretchy Velcro strap several times around the top half of the battery, took the bike for a 20min ride today, no glitches with the torque sensor, smooth power delivery in all levels right up to sport mode
Will see how it goes over the weekend on a longer ride to see what the range is like.