The Magellan series of Satnavs used to have a function for recording routes as they were being driven. These are probably a bit "old hat" now, but I am sure that there will be some up to date ones available - perhaps you could try in the hiking/trekking/Outward Bound shops? Alternatively, ...

I no longer have the slightest wish to contribute to this thread. You have completely misunderstood the points I have been making - so you charge your batteries as you think fit.

It’s not quite bas easy as that. Battery charging is a rather complex matter, and batteries should be treated with respect in view of their very low internal resistance and their ability to source very large currents (100s of amps in the case of vehicle batteries). Battery characteristics which can ...

An excellent circuit book is "The Art of Electronics" by Horowitz and Hill - available online from various retailers. The latest editions are somewhat pricey, but the 1st ed is still available and still good.

Don't forget to allow for fault conditions. One of the batteries could develop an internal short in one of its cells, and then that would unbalance a set of batteries in parallel without some form of individual current sharing.

Why not ask Maplins?

The best book I have come across is "The art of electronics" by Horowitz and Hill - available from online retailers.

Search for "soft start schematics" and "long period timers"

I think you need a grounding in circuit theory. The best book I have come across is "The art of electronics" by Horowitz and Hill - available from online retailers. BTW, in your diagram, if you are using a relay to switch the input voltage, surely the diodes are redundant?

The resistor wattage rating is the maximum that it will dissipate without burning out. Dissipating 4W in a resistor only rated for 2W or less is asking for trouble! Use at least a 5W one, or possibly even higher rated if the 5W one gets uncomfortably hot.