I have decided on a dual power supply, one for the Motors and their Drives and the other to supply the 'compute' aspects.

The 12V battery supply will provide for the Motors/Drive and the Lithium P for the compute.

These supplies need to be distribute and to save space I've created a 'Distribution Stack'.

This can be seen here.

Also to save space I've velcro'd the Lithium, the Lead Acid and the Solar Controller together.
Velcro is useful to tear things apart quickly.

These can now be connected together. You will note that one lithium battery is different, easy to change and replace because of the velcro.

You also see that solar cells for the Low Voltage supply connected.
While I haven't connected the Motors and Drivers up I have successfully connected the RPi and the Arduino boards and powered them up at the same time.
Not fully tested them but it does mean we are on our way,