Hybrid Battery Consumption Question.

[RunningInPleasePass]

I have a question that I have been pondering, I know I need to get a life, but can someone answer it please?

When you pull up, say, a red light, you coast to a stop and apply the foot brake and eventually stop, at that point the car is stood, assuming the engine is not running and you have not selected Park, are you using any HV Battery power to stand still?

[Grumpy Cabbie]

Yes

The a/c draws quite a bit when on full, but even if you turn the heating off the car is still running pumps for the inverter coolant and engine coolant. Then there's the computers and charging system for the 12v.

The car will probably sit in Ready with everything like heating switched off for about 40 minutes before the HV Battery runs down and the engine kicks in. I've found that things like leaving headlights on makes very little difference. The main draw/drain is the a/c and/or heating (a/c uses power to drive the compressor and the heating utilises a pump). You then have the added issue of the engine cooling down and the car firing up to warm it up.

So sitting in Ready isn't 'free', but is certainly better than leaving your engine running all the time like most other cars. (I'm also not a fan of the cheap stop/start systems employed by most manufacturers these days as most times you are rarely stationary for long at traffic lights. Most times you'll be crawling in very slow traffic or at the lights someone is always shuffling forward a little.)

[RunningInPleasePass]

Thanks for a very clear explanation.

As you say running the ancillaries is not free, I had been watching the HV Battery level the other day while stuck in traffic on the M62 and it never seemed to move.

On the same theme, when stood in the above example, is the Electric Motor trying to drive the car against the brake pressure?

[Aceshigh84]

I would also like to know about what happens to the brakes. I have found that if you let off the brake pedal a little bit, the lights will go off but you can hold the car stationary. Let off a little more and you can feel the car fighting the brakes.

I struggle to get that sweet spot, but I don't like having to use either park (because you can't just get underway quickly), or neutral (which means if the engine is running it isn't charging the hv battery), or worse yet sitting with the brake lights on.

[Whitewagon]

I would also like to know about what happens to the brakes. I have found that if you let off the brake pedal a little bit, the lights will go off but you can hold the car stationary. Let off a little more and you can feel the car fighting the brakes.

I struggle to get that sweet spot, but I don't like having to use either park (because you can't just get underway quickly), or neutral (which means if the engine is running it isn't charging the hv battery), or worse yet sitting with the brake lights on.

I thought the Auris Hybrid had a manual hand brake, if so use this it then alleviates all the problems you highlight.

[RunningInPleasePass]

Thanks for a very clear explanation.

As you say running the ancillaries is not free, I had been watching the HV battery level the other day while stuck in traffic on the M62 and it never seemed to move.

On the same theme, when stood in the above example, is the Electric Motor trying to drive the car against the brake pressure?

To try and answer my own question I've been looking at this:

http://prius.ecrostech.com/original/PriusFrames.htm

This explains what I wanted to know: What's Going On As I Drive?

Then read Creeping and Electric Starts.

The creep when you take your foot off the brake is simulated, no brake and no pressure on accelerator and the car creeps forward under power, so to answer my own question the car is not try to pull against the brakes.

[Aceshigh84]

I thought the Auris Hybrid had a manual hand brake, if so use this it then alleviates all the problems you highlight.

It does have a handbrake, but I would still have to put the car in neutral / sit on the brakes / find that sweet spot, otherwise wouldn't the car be trying to drive against the handbrake?

[Grumpy Cabbie]

I would also like to know about what happens to the brakes. I have found that if you let off the brake pedal a little bit, the lights will go off but you can hold the car stationary. Let off a little more and you can feel the car fighting the brakes.

I struggle to get that sweet spot, but I don't like having to use either park (because you can't just get underway quickly), or neutral (which means if the engine is running it isn't charging the hv battery), or worse yet sitting with the brake lights on.

I thought the Auris Hybrid had a manual hand brake, if so use this it then alleviates all the problems you highlight.

All hybrids have a handbrake. Being automatics they also have a Park option which is probably easier to utilise at the lights etc. Some people with an automatic like to put their car in Neutral instead and use the handbrake, but this should never be done in a hybrid as the car has no way of topping up the HV Battery. Continued use of Neutral with the a/c on could cause the HV Battery to go too low and cause damage.

It's all in the manual, but you'd be surprised how many people don't bother to read it.

[Aceshigh84]

It's all in the manual, but you'd be surprised how many people don't bother to read it.

Ouch! I hope that wasn't directed at me! :-)

As for using park at the lights etc, there are some people that suggest this a bad thing as if you are shunted considerably more damage is caused to the drivetrain as opposed to just body work because damage locking mechanism. This makes sense to me, until someone can prove otherwise, so I don't like to use it for short stops.

I cannot recall reading in the manual about how the HSD system interfaces with the braking system, whether they work in cooperation so that you can, for example, pull up at the lights, leave in drive with the brakes applied, put the handbrake on and the come off the brakes (still in drive), and not cause any damage or unnecessary stress to the car.

Also, I can't find reference in the manual to the sweet spot I mention, when the brakes are applied just enough to prevent creeping yet not blind the guy behind you - again, no mention of whether this causes extra stress to the car.

[Grumpy Cabbie]

It's all in the manual, but you'd be surprised how many people don't bother to read it.

Ouch! I hope that wasn't directed at me! :-)

Nah. I just meant in general. It's a common theme in forums of all sorts.

[Mr Lawrence]

I would also like to know about what happens to the brakes. I have found that if you let off the brake pedal a little bit, the lights will go off but you can hold the car stationary. Let off a little more and you can feel the car fighting the brakes.

I struggle to get that sweet spot, but I don't like having to use either park (because you can't just get underway quickly), or neutral (which means if the engine is running it isn't charging the hv battery), or worse yet sitting with the brake lights on.

I thought the Auris Hybrid had a manual hand brake, if so use this it then alleviates all the problems you highlight.

All hybrids have a handbrake. Being automatics they also have a Park option which is probably easier to utilise at the lights etc. Some people with an automatic like to put their car in Neutral instead and use the handbrake, but this should never be done in a hybrid as the car has no way of topping up the HV Battery. Continued use of Neutral with the a/c on could cause the HV Battery to go too low and cause damage.

It's all in the manual, but you'd be surprised how many people don't bother to read it.

Surely the engine kicks in before the HV Battery goes to low?

[barrycoll]

the use of P when in stationary traffic has been tackled quite extensively in past posts.....it is not a good idea, as the car is held by a dowl inserting into a toothed wheel, which would create mechanical havoc if you were thumped from behind....

as for using up e-juice while stationary, the best advice is to flip the car into Neutral, as Battery bars go down much faster when the MG1/2 is still pushing against locked wheels.....

the footbrake has high intensity rear lights which are painful on a wet night to the folks behind, and if you are thumped from behind, your foot willl come off the footbrake, and you will be pushed forward.....

always stop so that you can still see the tyre contact patches of the car in front, to allow room to go around if he breaks down, or space if he puts it into reverse by mistake

in short...........use the handbrake, and put the car in neutral

[Mr Lawrence]

Well ... I posted too soon. I reread the manual again and it does indeed say that the HV Battery can be completely depleted if you keep it in neutral too long.

Wonder why it's designed like this?

[RunningInPleasePass]

Well ... I posted too soon. I reread the manual again and it does indeed say that the HV battery can be completely depleted if you keep it in neutral too long.

Wonder why it's designed like this?

My guess is it's designed like this to distinguish between Park and Neutral, from what I have found:

In Park the engine is permitted to run when the Battery needs to charge, or just to warm up the car, but the car is locked in position by the gearbox pawl,

In Neutral the engine can start but not charge the HV Battery for some reason, but the car will roll if on a hill, it's just powered up to disengage the gearbox pawl.

This will make it imitate a normal auto car as close as possible I suppose.

When stopping at red lights for more then a few seconds, I think the the advice is, to leave it in Drive, apply the hand brake, and take your foot off the foot brake, just like any auto car.

[timberwolf]

Well ... I posted too soon. I reread the manual again and it does indeed say that the HV battery can be completely depleted if you keep it in neutral too long.

Wonder why it's designed like this?

Probably to avoid the need for a movable clutch and therefore to keep the mechanical design simpler.

[Grumpy Cabbie]

It's a common mistake, hence I decided to bring it up.

Only a Toyota dealer can recharge a HV Battery that has discharged too far. Then there is the worry you may have done some damage to it.

One other way you can run the HV Battery is to continue driving the car if it has run out of petrol. The car will crawl in electric which will allow you to safely get to the side of the road, but is not designed to allow you to keep going as the engine is unable to fire up to charge the Battery.

There a numerous stories on PC where owners have driven the car in this fashion until the HV battery was totally and utterly flat and potentially ruined.

1, Don't run out of petrol.

2, If you do, pull over when safe. The ev may be ok to drive a couple hundred yards to somewhere safer. Do not just carry on as far as it'll take you.

3, If filling up after running out of petrol you will need 10 litres at least before it'll fire up.

[Grumpy Cabbie]

the use of P when in stationary traffic has been tackled quite extensively in past posts.....it is not a good idea, as the car is held by a dowl inserting into a toothed wheel, which would create mechanical havoc if you were thumped from behind....

as for using up e-juice while stationary, the best advice is to flip the car into Neutral, as battery bars go down much faster when the MG1/2 is still pushing against locked wheels.....

the footbrake has high intensity rear lights which are painful on a wet night to the folks behind, and if you are thumped from behind, your foot willl come off the footbrake, and you will be pushed forward.....

always stop so that you can still see the tyre contact patches of the car in front, to allow room to go around if he breaks down, or space if he puts it into reverse by mistake

in short...........use the handbrake, and put the car in neutral

I would say not to do this as if you have your a/c on your will damage the HV Battery.

You're welcome to do it as it's your car and you're aware of, and keeping an eye out for a discharging HV Battery. Most people will not and could potentially cause significant, expensive and none warranty covered damage.

The a/c system on a hot summers day could chew threw the HV Battery in a matter of minutes. (1.5 kwh battery and 4 kwh a/c system).

But I recall this has been discussed at great length and like politics and religion, everyone had their own personal and strong views and were unlikely to change. Personally I leave mine in Park and if some fool is stupid enough to hit me in the rear and damage my parking pawl, then I'll be claiming off their insurance - simples :)

[barrycoll]

Well ... I posted too soon. I reread the manual again and it does indeed say that the HV battery can be completely depleted if you keep it in neutral too long.

Wonder why it's designed like this?

My guess is it's designed like this to distinguish between Park and Neutral, from what I have found:

In Park the engine is permitted to run when the Battery needs to charge, or just to warm up the car, but the car is locked in position by the gearbox pawl,

In Neutral the engine can start but not charge the HV Battery for some reason, but the car will roll if on a hill, it's just powered up to disengage the gearbox pawl.

This will make it imitate a normal auto car as close as possible I suppose.

When stopping at red lights for more then a few seconds, I think the the advice is, to leave it in Drive, apply the hand brake, and take your foot off the foot brake, just like any auto car.

I stand corrected, and that is very interesting Kevin/Grumpy , and many thanks...didn't know that ICE/HV charge was limited to P position, and no charge in N......live and learn

.....so why then, in a long M-way queue, when edging forward and eeking out the HV Battery, does the ICE kick in when the car is in Neutral, even when no a/c, heat, lights etc are needed...?

this is an interesting 'google' that confirms everything that I didn't know.....

Activating Inspection Mode

Other aspects of normal Prius operation affect our work out in the

bays. For example, there are times when we want an engine to idle

uninterrupted (for lack of a better description) for emissions testing,

engine or ignition analysis, warm-up and so forth. When the car is in

Park, this engine may idle, but only as long as needed to recharge the

HV battery, then it shuts off. Although the engine does idle in Neutral,

the system doesn't recharge the HV battery in Neutral

...it comes from this article about how to, and how NOT to service a Gen 2 Prius

http://www.motor.com/article.asp?article_ID=1376

[Grumpy Cabbie]

Engine temperature? This is also the way many Prii meet their maker when inexperienced, non Toyota garage change the oil. Car detects loss of temperature and fires up engine. Inexperienced garage wrongly assumed that as engine wasn't running that the car was off.

I haven't tried this but I wonder if you press the accelerator in Neutral whether the engine would start? If it did it would only be for a few seconds and doesn't rev very high.

I also understood (and I might very well be wrong here) that the Prius can't have emission tests or is exempt as it can't be manually revved to comply. Maybe they plug it into the emissions computer and let it rev it? Anyone care to answer?

[barrycoll]

http://www.thetorquereport.com/2007/04/toyota_prius_fails_emissions_t.html

this dates from 2007, but may be still relevant

after a 50 mile run this afternoon, using M-ways, and suffering the usual Mway queue, I sort of sense that N versus P, is a bit academic in normal usage.....

for me, N is for the short stop, were traffic is in the usual crocodile, and where there are bars left of the HV meter, and when there is no ICE start up, and where the use of D would need a wasteful braking restraint.....

but just maybe I am still wrong with this approach???

[Grumpy Cabbie]

It's your car. The only thing to be wary of as far as I'm aware is running the HV Battery too low. If you religiously keep an eye on it then I guess you'll be ok. If you got in the habit of Neutral but weren't looking then that's the danger. Again, in summer the a/c uses significant charge/draw (whatever the technical term is ;) ) and can run the HV Battery low very very quickly. It might not take much with the a/c on full to enter the danger zone.

[kithmo]

Hybrid Vehicles such as the Prius are exempt from the emissions test.

http://www.dvlni.gov.uk/Freedom%20of%20Information/Light%20Vehicle%20Inspection%20Manual/Exhaust%20emissions.pdf

[RunningInPleasePass]

Well ... I posted too soon. I reread the manual again and it does indeed say that the HV battery can be completely depleted if you keep it in neutral too long.

Wonder why it's designed like this?

Found this:

http://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

Read: Phases of operation - Neutral gear

These cars get more and more interesting!

[barrycoll]

a very interesting (and enlightening) topic....

I would have thought (maybe wrongly) that any Battery Management System, would prevent a harmful discharge, whatever the cause....

...and that the HV Battery would allow itself to go no where near a total shutdown, resorting to pure ICE until the vehicle is back into Regen mode of some sort

with my Bosch powered KTM e -bike, power assistance is available until the BMS decides enough is enough, and my own personal ICE is then given the job of propulsion.....harmful levels of discharge are not possible if the management system is working as it should

[Joseph D]

I have a question that I have been pondering, I know I need to get a life, but can someone answer it please?

When you pull up, say, a red light, you coast to a stop and apply the foot brake and eventually stop, at that point the car is stood, assuming the engine is not running and you have not selected Park, are you using any HV battery power to stand still?

FWIW, i almost never use neutral. When stopped at lights I just keep my foot on the brake pedal as this disengages the creep function. I'm not sure what this looks like on the Gen III, but you can quite clearly see the creep function turn off on the MFD when you push on the brake on the Gen II. If it looks like it's going to be a prolonged stop (in gridlocked traffic e. g.) then I will engage the park brake and press the P button.

As for blinding fellow motorists with my brake-lights, I have been behind other Prii, and don't find their brake-lights to be more bright than any other car (even at night), so I don't think people need to be concerned with that.