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I highly doubt it is the Hybrid Battery. They need to check the actual engine battery under the hood and then follow the pin point test below.
Was it a dealership or independent repair shop?
The Hybrid system is not something to pay with because it has very high voltage like the power lines on the power poles. The amperage can kill you if you do not properly disconnect everything to take the voltage out of the circuits.
The electrical system will need to be properly diagnosed per the pin point test I posted earlier. Guessing on these vehicle can get very expensive.
I would recommend getting a second opinion on the problem.