Charing the battery on an A8 50 TDI S line

I am a new member and have recently purchased an A8 50 TDI S line. As I am due to leave the country for 7 weeks in a weeks’ time, I thought that it would be sensible to hook up a battery maintainer. I thought it would be good to check out any quirks with the charging. I seem to remember having read somewhere about charging with a battery reconditioner charger, and the fact that these might damage the car. I know that these types of maintainer produce pulses that may spike way above the intended fully charged battery voltage, so I can see that there might be a problem there. Again, I seem to recall that the max charge voltage should be no more than 13.8V. I have not checked it yet but I am assuming that the battery is in the boot, so again I assume that there is a +V point under the bonnet. Other modern cars do not like to be charged at the battery terminals themselves but by using the +V point under the bonnet and a suitable ground. Has anyone got the low down on this, and can anyone recommend a suitable charger?🙂