Power for the PiPower

I bought PiPower battery backup for a Raspberry Pi project. My power comes from the 5 volt output of a DC-DC converter powered by a 48 volt battery. Can I power the PiPower with the 5V 3A available from power source without using the USB-C port? Are their alternative input pins?

Are you currently using pipower V3? It is recommended to provide a product picture for us to see.
The battery is recommended to use the two 18650 3.7V lithium batteries we delivered.
If you want to use a spare battery, the recommended specification is two 18650 3.7V lithium batteries in series.
You said 48V battery? What specification battery is it. It should not be compatible with pipower V3.

I am not replacing the battery. My power source does not does not have a USB-C connector. It is 5V/3A. I would like to connect it with + and - wires rather than use an USB-C connector. Is this possible? I am not sure what version my PiPower is. The only designation I can find on the board is 02602V21.

02602V21 is pipower V2 product.
If your power supply does not have a Type-C connector, but a DC connector, it is recommended to buy a DC to Type-C adapter for better and safer. If you do your own wiring, we can not guarantee whether it is correct and reasonable, if it leads to pipower V2 damage, you need to take responsibility for it.
Type-C power is everywhere Oh, is your usual cell phone charging Type-C power can be used.