Just Bought an '04 Prius, Now it has Battery Issues, Please Help!!

We'd be better able to help if we can see the data the hybrid battery is sending... For less than $30 you can buy a device that will allow you to connect your phone to your car and use Dr. Prius app to read the data. Here's a buyer's guide: Hybrid battery diagnostic and repair tool for Toyota and Lexus

 

It is much more likely that your multi-function display is losing connection with the car. Ask the previous owner if the MFD has ever been removed or swapped out. If it has been swapped, it may have the wrong model.

Your very first photo is clearly an MFD without proper communication.

Could be the connector(s) in the back of it are loose, could be a bad wire, could be a failing MFD.

and 2k for a 2004 with 148k is a pretty good deal if these other issues are resolved merely by replacing an mfd.

 

Without being there to actually see the car, I can't guarantee the condition of anything, but there is a button on the MFD labelled 'Climate'. I would imagine the MFD is in the signal path. Whether the steering wheel buttons bypass that or not, I can't answer with 100% certainty. Your first photo shows the A/C Auto icon is lit on your dash. Have you tried using the steering wheel buttons to change modes or temperatures? Normally the temp setting is displayed on the MFD, so even if the SW buttons work, you may not be able to see actual temperature numbers. Just hold the raise button down for about 10 seconds (that should max the setting) and see if the heater starts throwing out hot air. Assuming the car is warmed up already.

 

If you had a problem with the main traction battery, then there would be a red check engine light on the dash. This looks like an MFD issue and I suspect the reason you see a flat battery on the MFD is that it has lost communication and can't read the battery charge level .. just like it can't communicate with the AC.

As mentioned above it may be a loose connection on the back of the MFD. You should be able to find a video online explaining how to take of the panels to get to the back of the MFD. Once you have access ... turn the car on and in Park .. and then move the connectors at the back to see if the MFD comes on properly.

Also as suggested above ... get the diagnostic tool so you can check the the computer for fault codes. There may well be an error code and that will assist greatly.

 

OK....

Thing number 1.
Stop sweating over the battery.
Priuses have 2 batteries....the 12v "aux" battery and the 200v 'traction' battery.
201.6 volts....if you ask Commander Spock.
So....according to the picture of your malfunction display, both batteries appear to be functioning within normal parameters, as Lieutenant Commander Data would say....
The traction battery is just a spit can used to hold the waste energy generated by things like your braking and coasting....and (normally) it is designed to operate in the 20-80 percent state of charge range, and it will normally fluctuate between those values.
The true essence of driving EFFICIENTLY is not having ANY waste energy, so you should pretty much ignore the traction battery as an estimate on how the car is performing, or how efficient you are driving..
You can lie to yourself about being "more efficient" and stuff some extra amps into the battery by using various techniques like dragging your car to the top of a hill and coasting down, or using "B" mode - but you will learn about all of that in Prius-301, and right now you need to finish the basics class.
No condescension intended....
As mentioned above, if the traction battery were malfunctioning then your car would be an immobile object, and you'd have other lights and displays.
If you're able to drive the car (more than 2 miles)...then the battery is working.
For now....

So....the A/C (HVAC) and the MDF are different things.
If I had just taken my car to the dealer to have the A/C repaired and the heater wasn't working after I got the car back, then I'd go active on the service advisor, especially if they charged more and about $100 to "fix" your HVAC....but be warned!
Gen 2 Priuses have problematic Multifunction Displays.
THAT might be the whole problem and you may wind up with a large repair bill to replace a non-working MDF when it was just a loose connection in the back - etc.
This forum probably has some tips about troubleshooting the MDF and the HVAC,
Concentrate on THAT first.
You will have time to play with the battery soooooon enough!

Good Luck!!