Nearly all radio transceivers run off of 12 volts (always confirm this with the manufacturer’s documentation). So while you need a power supply for running your radio off grid power it is unneccessary when running a radio off of batteries that deliver 12 volts such as traditional car batteries (sealed lead acid batteries) which deliver around 12.6 volts.
A radio that runs on twelve volts can be safely connected to a battery running 12 volts using wires with inline fuses.
The most important thing to understand when using batteries is how long your radio will run on the battery. This means you need to know four things: how many amp hours the battery supplies and how many amp hours your radio consumes with listening, transmitting and in standby mode.
An Amp Hour (AH) measures how many amps the battery will supply for one hour. Generally car batteries supply about 48AH. So if your radio consumes 1A while listening you can listen for 48 hours. If it consumes 5A when transmitting you can transmit for about 9 hours. If you’re transmitting and receiving…do the math. Batteries become less reliable in powering equipment as they lose energy. Generally you don’t want to drain a battery below 15% of it’s power or your radio equipment may start functioning in odd ways as the power being discharged from the battery becomes less consistent.