Prius not switching into EV mode - 12v battery

Right back at 'ya.....friend.

 

Happens with me too, I thought it was something engineered in it. Whenever I drive fast, for longer periods, the car won't go into EV mode and the engine will turn on full throttle. I always thought it's normal, I have Aqua too 2012 that is

Posted via the PriusChat mobile app.

 

Do you think it should be replaced because of its age? Because it's a gel battery isn't it?

Posted via the PriusChat mobile app.

 

So now that you know that HV battery fan was the issue, can you please share a few details how they cleaned the fan? Because I need to do it myself, the Toyota dealership doesn't offer services for self imported cars.

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I generally regard 5 years as being the servicable lifespan of a car battery, and this FAQ seems to support that. And I generally prefer to pre-emptively replace the battery rather than wait for it to fail and potentially strand me somewhere.

 

It should be an AGM type, which is different than Gel.
If not abused, by being run completely down or by being left sitting unused for LONG periods of time, it should last well beyond 5 years.
But some do and some don't.
And there is no "load test" applied by a starter like with a conventional car.

At 5 years, I'd be having it tested and at 7 years replaced just on age.

 

Yeah, I just got a load tester for my 5 year old battery - it's one of those meters with a super heavy duty resistor to draw around 100 amps from the battery and measure the voltage. I figure if it can light up that resistor without the voltage dropping too far then it'll be fine to put out the dozen or so amps needed to run the computer and flip a few relays so that the hybrid battery engages. Beyond that point the state of the 12V is largely moot.

I've taken my first reading and I'll be testing it every few months to see if it shows any signs of degrading.

 

That's only partly true.

These really are NOT "12 volt" batteries. If the initial voltage is 12,0 volts, then it is half discharged already.....and that is NOT good, no matter how much current it will deliver or how much additional drop there is.

The initial voltage needs to be at least 12.6 and a really good battery with a healthy charging system will read 12.8 to 12.9 after sitting overnight. That is for a modern AGM type battery which they all should have.

 

Sure, the "12V" label applied to these batteries is just an nominal value. But measuring the health of a battery solely by its no-load voltage can be very misleading, since the voltage can drop very significantly when a load is applied. This is especially true for batteries used in conventional vehicles because of the extremely high load that the starter puts on the battery.

Hybrid and electric cars, on the other hand, put only a relatively modest load on the 12V systems, so the voltage drop won't be anywhere near what you'd see in a conventional vehicle.

I know that the battery is performing just fine right now, and my aim is to be able to detect any degradation from its current state so I can replace the battery before it's no longer up to the task. You can't do that without measuring it, and IMHO tracking how it performs under load is a good way to do that.

 

No load voltage tells you virtually nothing IF it reads "good".
It certainly does tell you something if it is LOW.
Might not mean that the battery itself is bad but it means that SOMETHING isn't right........and it often IS the battery itself.

My point is: You need to pay attention to the starting voltage AND the voltage drop when doing a load test.
In general, if the starting voltage is 12.2 or less there is no need to do the load test at all. Either the battery has a high rate of self discharge or something is staying ON when it shouldn't.

 

Yup, can't really argue with any of that!