Will the Prius still work if Battery needs replaced?

In case the traction battery is completely gone the car would not move at all, because there would be no way to start the ICE. This is done by MG1 which draws power from the traction battery. If the traction battery is on its way to eternity but still able to provide enough power to start the engine, then it would go, but there will be very limited power and you could have serious problems during acceleration.

Your second question is hard to answer. I myself would inspect the battery visually at first, looking for any sign of corroded contacts or leaks coming from the modules. I would measure the voltage of each module individually with a voltmeter and look for any significant discrepancies (anything bigger than approx. 0.05V apart would be a reason to worry).

During a test drive, I would look for any wild variations of SOC (State Of Charge), which would be a bad sign - and as the last test, I would try to force-charge the battery (press the brake pedal firmly while in "D" and floor the gas simultaneously, the battery would charge by the ICE) to eight green bars (full SOC) and will try how far would the car go solely on electric power. If it is properly warmed and in S4 mode, it should go electric even if you have no "EV" button in place and unless you press the go pedal too much. With eight greens, it should go at least half a mile or more at a steady speed on a flat ground, before engaging the ICE again.

If the car passes all these tests, I would say your odds that the traction battery will last for another 20 or 30kmiles are reasonably good. If you go for a Gen I (classic) Prius, then I would prefer some with a gen II battery pack in place (they are interchangeable, but gen II modules are much improved over the first generation). Any gen I with its original traction battery pack still in place would probably worry me a little, although it could be all right too.

 

I think to stay within your $8K budget you would be better off buying a non-hybrid. There have been battery problems on some of the Gen1 Prius but information is hard to come by because it's hard to find data on reliability once the cars are are out of warranty. The Gen2 batteries seem much more reliable.

Check out Bob Wilson's post #24 on this thread: http://priuschat.com/forums/gen-iii-2010-prius-technical-discussion/78970-hv-battery-salesman-says-3.html He has included some good references.

 

Agreed. All of that $8K should be used for buying a reliable drive train and chassis, not spent on a questionably-old high-voltage battery. Look for a recent Kia or the like. Save up to pay cash for a new Prius in the future.