Hi
well to report back. I have bought a smart charger. and left it hooked up. It took 3 days to charge up!! and that's with a 5 amp charger. but the test now shows 98% SOC and 100% SOH
so it looks all OK. whew.
yes, the missus was reading the manual incorrectly. It doesn't say you can't remove it. some AGM charging systems use a method of counting the number to times it has been charged. the withing system also looks very peculiar with black and brown leads coming off the positive and negative terminals. ...
European system no doubt.!! Anyway, I took a photo of it so should be able to reconnect the same way.