I often use small 7 or 9 Ah lead acid batteries because they are convenient and inexpensive. For example, my AllStar node at home is plugged to a battery like the one on the following picture With this battery I can continue to transmit for a few hours even when there is a power outage.
The following PCB turns a common sealed lead acid battery (SLA) into a convenient power source for radio equipment or other electronic projects. Just slide the PCB into the batteries connectors and you can use a low power radio. You also have a USB connector convenient for charging your phone or logging device. This "Battery Monitor" uses a digital voltmeter allowing you to easily check your reminding capacity. There is a convenient 2.1mm barrel power jack for charging.
Schematic
PCB
Final result
This is now the battery monitor looks like once assembled and installed on a battery and ready to use.
You can download the Battery Monitor Gerber file and order your PCB from any PCB manufacturer.
I also have a dozen PCB left, and if you are interested I can send you one. Just send me an email. You can find my email address on my QRZ page.