If hybrid/propulsion battery dies, does the ICE still work?

[fozzy2926]

As title really. I tend to keep my vehicles for many years, and as such was wondering; if the hybrid propulsion Battery were to wear out and come to the end of its useful life after, say, 20 years since manufacture, would the RX continue to function as an ICE driven car? I appreciate that it would effectively become FWD, having little or no input from the rear axle electric motor, but would the car still work, as in getting from A to B? It may seem a strange question with the possibility of replacing individual modules - if that's the correct term - of the Battery, but with how little I tend to use a car, it probably wouldn't be worth it...if the car still ran. 

Many TIA for your thoughts or experiences,

Steve

[olliesgrandad]

The answer would be no from what I understand. My understanding is that you probably wouldn't need to get the whole lot of cells replaced in one go just the failed ones. 

[DrShockr]

As above, it wouldn't work as an ICE only car. The Battery starts the engine every time it stops, the Toyota/Lexus hybrid system has no starter motor as the electric motor spins the engine up for start which requires energy from the Battery.

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[jumbojake]

as above, the whole system is designed around the traction Battery.

The traction Battery is used to start the engine... the engine itself has little power at low revs (have a google for atkinson cycle engines), so needs torque of the electric motors  to get the car moving.

If you have concerns, have a look around on these forums for any problems, and for more history look at the same for the Prius ... Battery issues are very rare and if you keep up the yearly check (£56) then it is covered for 15years.   The biggest common gripe is brake calipers... that's one job you can easily do at home.

[Herbie]

Hybrids don't have starter motors or alternators and any item that would normally be driven by a belt from the ICE is electrically operated. It has to be this way because the petrol engine doesn't run all the time, so imagine, for instance, needing to turn a corner or steer round a bend with no power steering because the engine isn't running.

The 12V Battery boots the computers and does one or two other things and gets the car to the READY state, ie, the hybrid system is now up and running.

As already stated, there is no alternator so instead the 12V Battery is charged by means of a DC/DC converter, which takes the 288V to 300V of the traction Battery and steps it down to about 14.5V.

Similarly, the power steering runs via another box of electronics which converts the hybrid Battery voltage to about 48V this time if I remember correctly. And the aircon compressor is run by a 500V three phase motor, again powered by the traction Battery.

So to answer your question, no, it won't run as a petrol-only car; it needs three things to run - 12V Battery, ICE and Traction Battery.

[royoftherovers]

Herbie, are you saying that the ICE will not even start in the first instance ?

[Herbie]

6 minutes ago, royoftherovers said:

Herbie, are you saying that the ICE will not even start in the first instance ?

That's correct John.

The hybrid system uses MG1 to spin up the ICE to 1000rpm before applying fuel and a spark to fire it.

[fozzy2926]

Wow, what a wealth of knowledge. Thank you all, for such an interesting and comprehensive answer. 

All the best,

Steve

[Thackeray]

Purely hypothetically, I imagine it would be possible for the car to be propelled without the hybrid Battery. In practice, this probably happens much of the time.

I've realised after puzzling over this in the past that the power setup is a bit like one of those old diesel-electric rail locomotives. The ICE drives a generator (motor generator 1) and the generated electricity is used to drive MG2, which is directly linked to the road wheels to drive the car forwards. In addition, (unlike the diesel-electric) MG1 provides resistance to the ICE to stop it spinning freely in the planetary gearset and instead the ICE torque is also transmitted to the road wheels, along with the MG2 torque.

In practice, while cruising most of the torque comes from the ICE and a much smaller amount comes from MG2 and MG1. But to get the car moving from stationary, if the engine isn't running the car needs the Battery to provide power to MG2 to get the car moving. A short time after the car starts moving, MG1 will usually start the ICE.

So, in principle, once moving, the car could do without the hybrid Battery. But even if the hybrid Battery died suddenly at 70mph (not very likely) I imagine the car wouldn't just keep going because I'm sure the computer wouldn't permit it. And as Herbie has pointed out, there's no way to start the ICE in the Toyotal/Lexus configuration if the hybrid Battery isn't there.

 

[Herbie]

1 hour ago, Thackeray said:

So, in principle, once moving, the car could do without the hybrid battery

Not really, not to any practical degree.

There'll be no power steering and the 12V Battery will go flat, not to mention that as you say, the computers wouldn't allow it anyway.

[jumbojake]

I suspect that's why Toyota spent nearly 40 years developing the prius... they knew it needed to be bomb proof.   the good thing is that it is rare to hear of any problems.   Just be thankful Rover didn't design it

[Spacewagon52]

9 hours ago, Herbie said:

Hybrids don't have starter motors or alternators and any item that would normally be driven by a belt from the ICE is electrically operated. It has to be this way because the petrol engine doesn't run all the time, so imagine, for instance, needing to turn a corner or steer round a bend with no power steering because the engine isn't running.

The 12V battery boots the computers and does one or two other things and gets the car to the READY state, ie, the hybrid system is now up and running.

As already stated, there is no alternator so instead the 12V battery is charged by means of a DC/DC converter, which takes the 288V to 300V of the traction battery and steps it down to about 14.5V.

Similarly, the power steering runs via another box of electronics which converts the hybrid battery voltage to about 48V this time if I remember correctly. And the aircon compressor is run by a 500V three phase motor, again powered by the traction battery.

So to answer your question, no, it won't run as a petrol-only car; it needs three things to run - 12V battery, ICE and Traction battery.

Brilliant explanation!

[Thackeray]

20 hours ago, Herbie said:

Not really, not to any practical degree.

There'll be no power steering and the 12V battery will go flat, not to mention that as you say, the computers wouldn't allow it anyway.

If the engine is running, I'd assumed that MG1 will always be supplying enough electricity to power all the accessories as well as providing some power to MG2.

In practice the Battery can go sufficiently low that it can no longer add any current to that produced by MG1 (the computer doesn't allow it to go completely flat).

Here's one example where the car uses the Battery for as long as it can to add speed but the car slows down (but doesn't stop) when the Battery has no more power.

Of course, a faulty Battery is a different matter and the computers would probably not allow the car to run if there was no Battery power because of faults rather than because of minimum permitted charge.