Leonardthall, GREAT summary of the use of mAh, THX
one may wonder why there even could be a long debate about this in another thread
anyway, as regards precise mAh counting, you guys may have a look at the UC4H power brick, it measures current at a rate of 1kHz (could be increased if deemed relevant), so, this one does NOT miss to count current spikes 
(to the best of my knowledge, this is the only available (DIY) device which can do that)
Iād like to mention that filtering can improve mAh counting accuracy somewhat, but is not a substitute for fast current measurements, like the UC4H power brick does!
(this is simply because a filter is linear, while spikes and so on are not distributed symmetrically around the average)
In my experiments I got accuracies of 1-2 % without any calibration.
https://discuss.ardupilot.org/t/uavcan-for-hobbiests/16464/52
https://discuss.ardupilot.org/t/uavcan-for-hobbiests/16464/59