battery voltage fluctuation

[rednblackgemi]

symptoms:starter will not crank motor. battery shows 12.5volts under no load, say 4 example if i put a blinker on the batt. vol. reads 10.xx/9.xx in time w/ the flash.is this normal or is the battery, whilst showing 12.5 volts, stuffed in some other way? i had a mate try jumping the gemi with his landcruiser this morning and it still seemed as though not enough juice for starter: slow crank cutting out after a couple of seconds.i replaced the starter thinking it was the problem but now ...?i guess what i need to find out is if this points to a short somewhere or a stuffed battery.i hotwired across from batt. to switch terminal on solenoid for same result which i think eliminates the ignition switch circuit as a cause?
'81 TE gemini g161 5-sp. stock

[rednblackgemi]

thanx for the replies(!) well i decided the battery was stuffed, after charging the hell out of it it would start the car, just. even showing
'good" voltage and the lil colour condition indicator bein what it should. so i have learnt sumthin about batteries: u need the amps, not just the volts!!! now just gotta replace upper balljoints and bog a couple of holes and put the opel motor in...lol it was kinda good i replaced the starter motor as well cos i found a sheared engine mount in the process. anyway , bonza!!!
p.s strewth!!!