why only inspect everything with oil and filter changes only

Using a maintainer won’t hurt the battery (a maintainer or trickle charger or battery tender: they are all basically the same thing (regardless of what a lot of people will say), and only supply a very small current to the battery (you want it less than 4 or 5 amps (preferably between 1to 2 amps)) won’t hurt the battery or the car. If I was driving it like you plan to I would use one.
However, a cheaper and perhaps a more enjoyable alternative, would be to take it for a spin once a week. Of course, the Chicken Littles here will panic with that advice, but the sky won’t fall.

 

When you have the hybrid shop check the car out tell them Triple A installed a new battery and ask them to check to make sure it is the correct one and everything checks out and if it needs to be reset ( they will know what to do). DON’t worry, it is perfectly normal that 12 volt batteries need to be replaced every few years. The fact that the former owner stepped up and paid for it is one more VERY POSITIVE sign you have a good car, even if he/she didn’t know about the EV mode. There a plenty of members of this chat that don’t understand how the hybrid system really works (contrary to their own beliefs). Relax, follow the advice of the hybrid shop you have turned to and ask them any questions you may have.
You are experiencing one of the effects of being on PriusChat that is an unfortunate side effect: The “Chicken Littles” will take any excuse to turn any question into a catastrophe. Sorry, just one of the joys of living in today’s world.

 

If you have the owners manual, you can read about what TOYOTA says about it.
It's good driving around a parking lot, or moving the car in your driveway.
I use it 99.9% of the time in the mornings. I drive about 1/4 of a mile before I need
to get up to speed.
If it's cold, it won't activate because the car knows it's cold and will warm up the engine.
And if the hybrid battery is at 2 bars, or about to go to 2 bars, it won't activate because the
car knows it needs to charge the hybrid battery.

 

We’re doing about 5k kms yearly. Ours lives on a smart charger, steadily between uses. 12 volt battery’s about 8.5 years old now.

 

The standard gen3 Prius does go into ev quite a bit while driving. Automatically. The ev button, under ideal conditions, might drive the car one mile at 20 mph. Basically a party trick enabled by the ev button. I never use it.

Everytime you let up on the accelerator, go downhill, touch the brake pedal, go in reverse, stop at a light or stop for any reason, the gas engine shuts off and you are in ev mode. The electric motors are ready to move you instantly while the gas engine rests or is in process of starting again.

One of the two electric motors may start the engine at high rpms hundreds of times on a long drive. Another electric motor moves you instantly from a stop when the engine is off, always moves you in reverse and often becomes a wheel driven generator to recharge the battery.

The big advantage of a hybrid is it can temporarily store energy when slowing, when going downhill or even from excess engine power to reuse when the engine is off or when the engine needs help. Result, higher mpg and higher short term power.

When the car needs to accelerate the engine and electric drive motor team up to supply power for higher horsepower.
.

 

John Kelly of Weber University has an excellent video that explains exactly how Toyota’s Hybrid system works. It is very interesting and informative, and is useful in providing knowledge of the facts, and thus avoid confusion.
EDIT: I just reviewed John Kelly’s videos and realized that he gets way more technical than needed for most folks. A much better source would be The Car Care Nut’s YouTube video series on how Toyota’s hybrid system works. Much easier to understand and less technical information.

 

Sorry, but I’m going to take exception to this. “Everytime” could lead someone to believe their system isn’t working correctly. The system WILL shut the gas engine down SOMETIMES under these conditions, other times it won’t.
Additionally, while your statement IS true that under those conditions (the system relying on the electric motors) the car is in EV mode, it could be confusing to the OP in the context of whether the EV mode is operating correctly since the focus is on the EV mode button.
Not trying to be argumentative, just trying to prevent Janny from being further confused and having unnecessary concerns.

 

You are right sometimes the engine will continue running at a stop if the hv battery is discharged. Normally with a decent hybrid battery and typical 1-3 minute stops the engine won’t run. In fact if the engine runs a lot at stops it is a sign of a weakening hybrid battery.

The key point is the ev button is not an integral part of normal hybrid driving. In fact the gen2 did not have one.

 

The ice will run while the vehicle is stopped for many reasons: electrical load from accessories, temperature of the engine, hybrid battery state of charge (believe it or not even a very healthy hybrid battery needs to be charged when it has been used to provide power to move the vehicle).
Your statement could lead someone to believe that their hybrid battery is failing when it is perfectly healthy.

 

aye aye aye Just can't win for losing.... Everyone likes to beat a dead horse...

 

I see much confusion and inconsistency in this thread and elsewhere as to what "EV Mode" means. Is it

• When the EV indicator is lit due to pressing the EV button, or
• When power is being supplied to the drive wheels exclusively from the battery (which can occur even when the EV button hasn't been pressed), or
• When some of the power being supplied to the wheels is from the battery, or
• Any time the wheels are turning but the engine is not simultaneously providing power to them? Every car, even a stock Model A Ford, can do that.

Different people in different contexts seem to believe each of the above definitions is the correct one. It ain't that simple.

It's not merely a "party trick." It's a useful feature to enable moving the car a very short distance at slow speed when needed, without abusing the engine by running it only briefly.

 

The issue though, with stone cold engine it invariably won't allow EV mode. My workaround: plug in the block heater for at least an hour, works.

 

Perhaps if you read what the Toyota owners manual says about it, that will clear it up for you.

 

In the US, moving the car short distances in EV mode is allowed when the engine is above 20°C, assuming other reasonable conditions, are met.. That may not be "stone cold" by your definition, but it's useful even when the engine is as "cold" as it's gonna get on warm days. In other places, the 20°C restriction doesn't apply. Not sure about Canada.