Why does the 12V Prius battery drain so quickly?

Hello, I’m Pete from the Car Genius team at RepairPal. I’m sorry you’re dealing with this concern on your Toyota Prius. Based on the information provided, if after the jump start your vehicle runs and operates properly but after you turn off the engine and within 30 seconds it seems the battery is dead or weak as it needs a jump start to allow it to start again, this type of concern can indicate a pretty hard short to the battery itself usually caused by one or both of the battery cables being shorted out, a concern with the cables or connections themselves at and leading from the battery to where one or both cables have high resistance in them to where a jump start is needed, or in some cases even the engine starter to where the starter assembly is drawing too many amps to where it needs that extra boost from a jump start to allow it to start and run. I do not suspect there is an actual component draining the battery that can typically occur as usually if this was a normal drain concern it would take hours or days to drain the battery and with the battery draining or seeming drained in such a short amount of time I suspect this is one of the other concerns mentioned above. I do recommend having this checked into/tested further by a reputable repair facility that will have the tools and diagrams needed to perform the testing to pinpoint the concern if possible. If you’d like to find a trusted, certified repair shop in your area, you can check here: https://repairpal.com/certified. If you need more advice, or have any further questions about your vehicle, we’re here to help. Just give us a call at 877-913-1554 where we will be happy to assist!