Sometimes it is convenient to trade some cargo space for extra battery capacity. I repurposed the original starting battery that the group-31 upgrade replaced.
Back-country travelers are using Amateur Radio for wilderness communications because of the greater range. Many have a Citizen Band radio because it is ubiquitous even though the range is limited.
To charge our Casita travel trailer, Cocoon, we added a power connection to Campbell, our Toyota Land Cruiser. We also added a power distribution center in the cargo area to run additional gear.
We want to use our microwave when we are boondocking in Cocoon, our Casita travel trailer. We need an inverter for that but do not want to add a new load to our single 100-amp-hour house battery.
One fuel tank, two uses. When space is limited having gear that is dual-use is critical. We need and external fuel tank for the generator at base-camp and a spare fuel can for Campbell on excursions.