more starting issues... voltage issues help pls..

Ok so i had another thread going recently in which i redid my entire wiring to the battery in the hatch

have some new issues... im thinking it may be a bad battery

The car wont crank on 12.5 volts, battery is charged 100% ...when i charge it it makes weird gurgling noises is that normal? its a interstate battery

so i put my battery charger on it and if i use engine start, it still wont start, however when i put it on charge mode, it raises the voltage up and car starts right up, i can then take the charger off and start car repeatedly until im back down around 12.5 volts then it no longer wants to start and i have to hook up charger again

anyone have any idea why this could be????? is 12.5 volts where a battery usually sits after resting a while?

i tried another battery but i think it was a bad battery...

i had the battery tested 3 times and it came up good each time, however i bought a new battery and now it starts right up.. must have had some bad cells or somethin