When you are actively charging the batteries off a solar panel for example, it will be even higher, up to 17V or so I think. The automotive PicoPSUs only cost a little more and will smooth it out up to 24V I think… there are even some models that go up to 48V.
Edit: why the down-votes? Is this incorrect?
There is also an open-source alternative to this: https://github.com/matanui159/ReplaySorcery
Although it seems to be no longer actively maintained.