My 5 in 1 battery consumption has increased over the years and become a pain. Today I converted it to solar powered, and it seems to be working beautifully. I wanted to share with the group the key component that made it an easy mod.
https://www.amazon.com/gp/product/B00ODL140M/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1That link is to a 12vdc to 3vdc regulator module. It's only $7, and worked very well. As a bonus, the entire module will fit in the 5 in 1 battery compartment with a little modification. The only modifications necessary are to rip out the divider in the battery compartment, and clip off the screw mount tabs on the module. Once you do those things, it will fit snugly in the compartment like it was made for it.
The battery compartment divider is very thin plastic. If you start with a couple of cuts with diagonal cutters, you can go in with some long nose pliers and roll up the divider like an old sardine can lid (hey, I'm old).
There is plenty of room to run the wiring into the body of the unit. Just solder the module output to the existing tabs that the red and black battery wires are already connected to. No need to modify anything, just tack them on to the existing tabs.
In case you were unaware, the 5 in 1 runs on 3vdc, running 2 sets of batteries in parallel so you can change them one at a time so as not to electrically drop the system while changing batteries...that was he plan anyway, but the series/parallel arrangement explains how you get 3 volts with 4 batteries.
The rest of the system is straightforward and I won't go into it here, but this is a way to run your system off of 12vdc from any source.
Disclaimer: If at some point they modify either the 5 in 1 or the regulator module, it might not physically fit for you, but it was perfect in my case.