Optimiser warning light

[bodgit]

I,ve lost the instructions for my optimiser and need to know what the amber warning light is indicating. It starts off as normal on amber then goes green but after a day or so goes amber. This has happened the last few times when charging as I have to swap every 5 days between bikes.
It only happens on my cbr not the sp1 but it starts up fine with no warning lights coming on.