Hi
Only had my bike 14 months and its started cutting out. The bike rides fine until i start uphill and then i lose all power so i have to turn the key off/on to get it going again but the problem becomes more frequent after that, even cutting out on the flat.
Just wondered if its a motor or battery problem? Any advice would be helpful.

Model: cyclamatic power plus/250 watt brushless motor/lithium-ion battery - 24V and 10A.

Are you pedaling when you go uphill? A 250w motor won't be able to take you up most hills without pedaling. You need at least 400w. I just wanted you to have an idea of what your bike is capable. Nothing wrong with a powered-assist bike.

It sounds like one of your cells might be weak or damaged and it's hitting the Low voltage cutoff of either the BMS or the controller. Don't throw the battery pack out. It's probably still good if you can find which cell is damaged and replace it.

The battery pack is probably tripped the BMS LVC mechanism. You could either try to replace one of the cells that is damaged or weak or you could probably take off the BMS circuit board if you can find it and replace it with something else like an Celllog 8s monitor from hobbyking.com . And hook up your own alarm to it. The reason why there is a BMS on it is to prevent you from discharging the battery below the 2.5v per cell or 3.0v per cell if it's a different kind of lithium chemistry . You could put a celllog monitor on it and wire this up yourself possibly. I don't know what your battery pack looks like though. This will only fix the BMS so that you can still use the pack. Your 24v pack will probably be only 21V if you have a dead cell but it will still be operational as long as the controller doesn't have a LVC of its own.

(Having experienced some of the same observations, I would check your battery connector connectionss and assure that they are corrosion free, brushed occasionally, and have no play at the mating connection of the battery to the wiring harness. The press to fit connectors can make and break electrical connection as vibration of the ride moves things around. Good luck erider!)