Cold car won’t start

Your battery loses voltage in extreme cold. When it warms the voltage goes back up. All modern cars draw power constantly but some top batteries maintain their voltage better. The problem is worse if you don't drive it everyday. 8 volts is really discharged. The ideal solution is to put a battery maintainer on it overnight to ensure a full charge and keep the charger on it if it won't be driven for several days. Even with a "new" battery. Any battery can discharge overnight under some conditions like the rear hatch not completely closed.

 

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How many miles on the vehicle, and how many hours per week do you drive it?

If the Prius didn't come with Toyota owner manuals, go download them here : Toyota Warranty & Toyota Manuals | Toyota Owners

Though your issue could be a simple 12v problem, generally speaking when there are warning lights displayed on the dash, there will be OBD2 codes (DTCs) stored in the ECUs. Without spending $$$ for a dealership diagnostic, many prefer using a 'Mini-VCI' cable (20 usd) and TechStream (dealer technician software) installed on a windows device to scan for OBD2 codes. Others will use a simple bluetooth adapter with an App like Dr Prius or Hybrid Assistant, neither are as robust as TechStream.

If the problem doesn't resolve and once you know the OBD2 codes, you can post them here for additional guidance and help.

Don't forget to check the engine oil often, especially if you're a spirited driver.

FYI : your posts are being moderated until you've reached a total of five (5).

 

Just because the battery is "brand new" does not necessarily mean that it can't be BAD.
Hopefully it just was not charged properly before being installed and a good charge will fix the problem.
After that, the charging voltage should be checked while it is running (ready).

It is also possible that one of the main battery connections is not clean and tight.

 

Because the hybrid computers are starving for 12v power. Be a good owner and fed them.

 

Red car icon is usually failed hybrid battery odds are good it has failed again.

Refurbished hybrid battery’s are quite a racket.