If the radio is original, and you don't have the code in your owners manual, register on Honda.com owners resources. You will need the vin to retrieve the code, plus recall information
Don't you need the serial number from the radio and the VIN number to get it? Seems like I remember reading in one of the manuals that you needed both to get your radio code.
Just make sure your radio is OFF when changing the battery. Twice over the last couple of years, I have forgotten to turn off my maplight and it drained my battery. Put the charger on and radio was ok, JMHO. Look for white sticker with radio code, under ash tray/inside glove box/under hood fuse box lid, these were some of the places they were hidden, good luck.
David g...................
If you run jumper cables from another battery to the car's cables on the battery before you take the old one out, you won't lose anything. You just need to maintain power to the system.