Alzibiff

I have had a similar problem on one of the two Kalkhoff Agattu Excite bikes which we bought last August. On four occasions, the bike has effectively reset itself - mileage goes to zero, clock goes to 00:00, and when I push it out of the garage, no speed shown on the display. This has happened after I have had the battery out for a day or so and wondered whether it had anything to do with the system backup battery losing its connection. (There must be a battery somewhere which keeps the clock ticking when the main power pack has been taken out). After a while, I can get power assist but not until I have gone through the gears a couple of times - I cannot see any rational explanation for this! My dealer is also perplexed but has agreed to swap the “head unit” under warranty in the hope that this fixes it. I cannot find any technical detail online but what IS the function of the head unit? Is it more than just a display? I should add that there is no problem when out riding so I have ruled out any intermittent connection issue when the power pack is fitted.