Welcome to the CPL AGK question and answer forum. Please feel free to post your questions but more importantly also suggest answers for your forum colleagues. Bob himself or one of the other tutors will get to your question as soon as we can.
bloodandiron replied the topic: Battery ampere hours
It's been a couple of months since I last sat AGK so my memory of it will be a bit rough, but I remember there being a question where a list of instruments and their load in amps was given. You had to calculate how long the battery (its amp hour capacity was also given) would last given the list of electrical loads. The answers available were along the lines of 4, 4 1/2, 6 or 7 hours.
In that case, all you need to do is add the amps drawn by each instrument and get a total for all of them. Then divide the capacity of the battery (which would be given as a number of amp/hours) by that total.