Hello,   PERC battery replacement is, fortunately, pretty easy. It is something that requires a maintenance window, however. What you'll need to do is shut the server off, remove the top cover, and then identify your PERC controller. It will have SAS cables connecting it to the backplane. You should also see another smaller cable and header. This smaller cable and header will be for the battery. You'll just want to unplug the cable and remove the battery, then replace it. You can then return to normal use. You might also check OMSA to see if it shows a learn cycle for the battery.
Hi. I think i am getting somewhere thanks to all your help.  I have an orange flashing light on the front panel. Where do i find the cause please? Graham
T310 flashing orange on front panel