no power, low batter on mfd, red triangle light

One thing to check is the inverter coolant pump. If the inverter overheats it will cause similar problems. Open the inverter coolant reservoir and with the engine running verify that you see flow or turbulence in the reservoir. If you do not see any flow or turbulence you may have a faulty coolant pump.

If you do see turbulence then you are back at the 12V battery and possibly the HV battery. You will probably need to get it to a Toyota dealer and have the DTC's read to indicate where the problemmay be.

 

What were the outside temps when this was happening? Did you hear the battery cooling fan in the back seat? In Florida, I would not think you would ever see more than the standard 5 or 6 blue bars on the MFD, as going all the way green full with a good battery usually requires a real hill. It does happen that the control systems will turn down the juice to avoid overheating, and from time to time I have noticed some sluggishness in my car. But it has always passed quickly. If you do see green bars often, and then they drop quickly, that is a sign of HV battery trouble looming large. As has been mentioned by Seilerts, parking the car in the sun with an almost full battery causes an exothermic situation that is bad for battery life.

 

If there is a DTC set, and the battery is implicated, then they would diagnose and possibly replace under warranty. If it is not something under warranty, then I guess you would pay their diagnostic fee.

From my reading here, it looks like the highest likelihood of HV battery problems come from the hottest parts of the country. Keeping the car cool while parked is a really good idea for many reasons, especially battery health. I just got a reflector for the windscreen, and am amazed how much difference it makes.

 

I just got a generic $10 large size folding reflector from NAPA.

 

The Prius does not have an alternator. It has a DC to DC converter that converts the supply from the HV battery around 201volts to around 14volts to charge the 12volt battery.

 

Buy the windshield visor they sell here at Prius Chat Shop. Mine's lasted almost 5 years so far. Its the best shield I have ever owned. Its insulated and has kept its shape and custom fits the dash. Also use the pull out package cover in the trunk too. That keeps the sun from baking the trunk area. And if in Florida its a must to have a good window tint. Tint as dark as allowable. If none of the above man oh man thats a hot car in Florida sun. Very bad for Hybrid battery.

 

What do you mean AC "drained the battery". I live in Florida too and the AC is never off and no battery drain unless you mean the Hybrid battery goes to one purple bar if you sit for a while with the ac & radio on. That's completely normal and the car should charge the Hybrid batt right back up to 2 or 3 blue bars in a mile or so. But please describe what you mean.

 

Just to throw out a guess, it sounds like the ICE is not putting out the power that it should be. There is a speed, on straight and level road, at which there are no arrows going into or out of the battery. (That will also be the most efficient steady state speed, as nothing is wasted in inefficiencies of the electronics. I don't get to find out what that speed is here (no straight and level!)).

At high speeds on the flat one should not be using anything from the battery for motive power, on the average. If the battery gets lowered at what is a normal speed, then it says the engine is not doing what it normally does, and is drawing down the battery like it does on a hill. How about throttle body and MAF cleaning, and plug replacement, could those be a factor?

 

It is common to not get all the air out of the coolant loop after replacing that pump. This leads to the inverter overheating and shutting itself down. Given your symptoms and history I'd tell the dealer to start there.

 

It's not surprising. The weather is hot now which creates a double whammy: the inverter is running harder to power the A/C and therefore generating more heat, and it's more difficult to cool because the outside air is warmer.