Leisure battery's query

Hi all
I have a query re my leisure battery's which I hope someone can help me with. I have a Warwick xl picked up in March 2015,it has a Sargent control panel which as far as the leisure batteries go has a gauge I have never seen before along with the volt gauge which shows the battery has say 12.8 volts or whatever it my be there is a percentage amper hour (AH) gauge which shows the percentage of amperhours available 0 to 100 percent which as I say I've never seen before. This gauge has been showing between 80 & 90 percent since I've had the van. But after leaving the van on the drive for about 5 weeks it dropped to zero, I've had the van plugged in for 3 days now and it's crept back up to 63 percent, the voltage guard is showing 12.8 volts as this is all I've had in the past I would not have worried till now. My questions are What is the gauge showing me? Could the sudden drop and slow rise show I have a problem with one or both my leisure batteries, Should I just ignore it. I should say I do not always camp with electric I spend as much time as I can off electric.
Sorry if this is a bit long winded, also after about 20yrs motorhoming I still do not understand electrics that well even though any have tried to explain it to me. Many thanks for any help.
My questions are what is this gauge telling me

It sounds like the leisure battery/s went flat and if so the battery may well be knackered. Mine (two batteries) takes a good two days on electric from 80% capacity showing on gauge back to 100 so yours from flat will take quite a while.
The voltage should be getting over 13 and up near 14 when you get to 100%.
If the same as mine the sergeant unit tells you what the charger is putting in to the battery which will be a good indication that it is actually charging.
Give it a couple more days and see how it goes 

Usually a good drive should charge everything up. You could try a site with hookup, but don't connect it straight away. Run it to see how long it lasts, with the hookup available just in case.