Using the Charge settings to reduce engine on/offs

[Lior]

Hi,

I want to bring up two examples before I ask my question:

1. When on a long drive. If for instance I have 100KM left to drive and the battery is depleted, the battery will charge to 2KM and then the engine will shut off for a minute or so until that charge is depeleted. Then it will turn back on. This can happen dozens of times during the drive!

2. In my home town, which is on a hill, there are plenty of traffic circles. If the battery is depleted then the engine will shut off every time i stop uphill and restart when i start driving again. This means about 6 engine stops in only 1KM of road!

Now to my question -

All the engine start/stops is getting on my nerves. I am afair that all the starts takes its toll on the engine, plus its just annoying. I am wondering wheter it is smarter to set the car into charge mode, in which it will keep the engine running and then move back to normal mode once its gathered enough charge to cruise for a significant time (10KM? 20KM? depends on the time left for the drive).

I am not certain though, how the car behaves in charge-mode. does it spend extra gas or engin revs to actually charge the battery beyond what is needed to get the car moving at the current speed? Will it idle higher than it does in normal mode?

Is my logic sane? or is there a flaw?

Thanks
Lior

 

[richr]

Have a read of the Mitsubishi technical documents on this forum. It might give you some insight into what the designers intended. The engine is highly modified from the basic 4 cylinder unit used in other Mitsubishi cars to tolerate stating and stopping every few minutes. Personally I can’t tell that much whether the engine is running or not a lot of the time - most of the noise for me comes from the tyres and the radio. So I tend to just let the car manage where the power is coming from and not worry.

 

[michael8554]

Up to about 100Km/h speed on the flat the car will run ev, but faster than that, or uphill, the ICE will run.

Once charge runs out the car will cycle between ev and ICE as you describe, unless you intervene.

CHRG mode starts the ICE and runs it at it's most economical steady rpm to turn the generator which will then power the car, so CHRG back up to 70%, then switch back to ev.

In SAVE mode you are mostly powering the car with the full rev range of the ICE, which is less economical than CHRG, but of course there are times when you want to SAVE, say, 10Km of charge, for ev driving through your destination town for instance.

Out of town run in B0 and coast when possible, but increase the B setting to regenerate on steeper hills, or gently brake which also regens - but not too hard or you will engage the disc brakes.

In stop-start conditions in town use B5 to brake, or gentle use of the foot pedal.

 

[Lior]

Hi guys,

thanks for the detailed responses!


Lior

 

[ThudnBlundr]

The car runs what is in effect CHRG mode till it's added a small bit of range, then goes into EV mode. As you noticed, it goes through that cycle unless you do something else.

Another thing to be aware of is that CHRG mode is less efficient when running in Series mode below 40mph/70kph where the ICE charges the battery and the battery drives the wheels. Above that speed it switches into Parallel mode, where the ICE drives the front wheels directly, and any spare power goes to the battery.

A final thing to consider is that the charging rate drops as the SOC gets higher as the battery cannot accept all the power generated. That's why regen is so poor at high battery readings. So running CHRG or SAVE when the battery is above 75% is also less efficient.

So running CHRG is no bad thing as the car will in effect do it anyway for short periods. Running CHRG on the highway is more efficient than running it in town, so try to use EV around town if possible. Using SAVE is another option rather than using EV on the highway, as continued high power drain is believed to be bad for battery degradation. SAVE is no less economical than using CHRG in the same situation as it uses exactly the same mechanisms, but again it's better to use CHRG on the highway than use SAVE in town. Whatever mode you use, for greatest efficiency you should aim to arrive at your next charge with no EV range left.

I'm not sure why people have this obsession with B0 as you can coast in any 'B' setting simply by ensuring that no power is going to the motors or being generated by regen. You can see this when the power needle is flat, but it soon becomes easy to find the coasting point on the accelerator by feel. That way you can coast when you want to and have full regen if needed - the best of both worlds. (Actually coasting does send a tiny bit of power to the motors, but it's only a couple of kW at highway speed.)

Having said all that, the PHEV has been designed to be efficient when simply left in 'D' and I've seen no scientific evidence of greater economy or longevity by playing with the settings. Certainly leaving it in 'D' delivers decent economy. But I enjoy trying to get more out of the car - YMMV

 

[michael8554]

If I coast in say B1 and then switch to B0 the car goes faster. B1 is regenerating with foot off the accelerator, B0 doesn't so is truly coasting and the car is using no power to do so.

Having said that I have no evidence to prove that coasting 500 metres in B0 is more efficient than 300 metres in B1.........

 

[greendwarf]

If I coast in say B1 and then switch to B0 the car goes faster. B1 is regenerating with foot off the accelerator, B0 doesn't so is truly coasting and the car is using no power to do so.

Not quite true, as to achieve "no drag" coasting in B0 a small amount of energy is being used - try coasting in B0 and then switching to N. The car slows but without regen. :?

 

[michael8554]

[/quote] try coasting in B0 and then switching to N. The car slows but without regen. :?[/quote]

That makes sense, but I would consider N to be a unusual driving mode.

 

[MadTechNutter]

I'm not sure why people have this obsession with B0 as you can coast in any 'B' setting simply by ensuring that no power is going to the motors or being generated by regen. You can see this when the power needle is flat, but it soon becomes easy to find the coasting point on the accelerator by feel. That way you can coast when you want to and have full regen if needed - the best of both worlds. (Actually coasting does send a tiny bit of power to the motors, but it's only a couple of kW at highway speed.)

I certainly can't keep the needle perfectly flat in any B setting other than B0 without constantly staring at it. You must have mirror flat roads because the slightest road level change will require compensation. Alternating between accelerating and regeneration in order to try to keep that needle straight will incur thermal losses* that are higher than just freewheeling in B0.
A constant small amount of energy in B0 to compensate friction makes sense.

*I don't have any figures for the PHEV and it would be highly load dependent but a ball park figure would be 70-80% regen efficiency. So if 1kWh goes out of the battery 0.8kWh is absorbed again from regeneration if no energy is accounted for drag or acceleration, although at very low levels the efficiency might reach 90% but that would be really stretching it.
Resistance is everywhere and always incurs thermal losses unless it is a superconductor.

 

[michael8554]

I'm not sure why people have this obsession with B0 as you can coast in any 'B' setting simply by ensuring that no power is going to the motors or being generated by regen. You can see this when the power needle is flat, but it soon becomes easy to find the coasting point on the accelerator by feel. That way you can coast when you want to and have full regen if needed - the best of both worlds. (Actually coasting does send a tiny bit of power to the motors, but it's only a couple of kW at highway speed.)

I certainly can't keep the needle perfectly flat in any B setting other than B0 without constantly staring at it. You must have mirror flat roads because the slightest road level change will require compensation. Alternating between accelerating and regeneration in order to try to keep that needle straight will incur thermal losses* that are higher than just freewheeling in B0.
A constant small amount of energy in B0 to compensate friction makes sense.

*I don't have any figures for the PHEV and it would be highly load dependent but a ball park figure would be 70-80% regen efficiency. So if 1kWh goes out of the battery 0.8kWh is absorbed again from regeneration if no energy is accounted for drag or acceleration, although at very low levels the efficiency might reach 90% but that would be really stretching it.
Resistance is everywhere and always incurs thermal losses unless it is a superconductor.

MTNutter, I agree.

 

[ThudnBlundr]

If you're truly coasting in B5 and switch to B0, there will be no difference because it uses the same mechanism in each case. Between the postion which supplies power to the motors and the position that regens power from the motors is the sweet spot for coasting. In B0, that's with no pressure on the pedal. Upping the 'B' setting remaps the throttle so that the coasting point moves each time and more pressure is needed. If you're slowing down noticeably in any 'B' setting, you're not coasting. Of course you will very slowly decelerate on a level road while coasting, but I certainly can't feel it.

You must have roads with no bends or traffic, because I cannot coast for long without having to slow down or speed up, so coasting for long distances is irrelevant. Also coasting has nothing to do with the steepness or otherwise of the road, so I'm not sure why that's relevant: if I come to a hill, I need to apply power to maintain speed whatever 'B' setting I'm in. And I must admit I tend to drive based on what the traffic and road conditions allow rather than simply coasting for coasting's sake.

 

[quenthal]

So running CHRG is no bad thing as the car will in effect do it anyway for short periods. Running CHRG on the highway is more efficient than running it in town, so try to use EV around town if possible. Using SAVE is another option rather than using EV on the highway, as continued high power drain is believed to be bad for battery degradation. SAVE is no less economical than using CHRG in the same situation as it uses exactly the same mechanisms, but again it's better to use CHRG on the highway than use SAVE in town. Whatever mode you use, for greatest efficiency you should aim to arrive at your next charge with no EV range left.

In general, isn't SAVE more economical than CHARGE when in highway?

Say I'm driving 150km of highway with very low battery. Should I use SAVE or CHARGE, if I know there is 20km left to drive under 70km/h in town or similar?

 

[ThudnBlundr]

Both SAVE and CHRG use exactly the same mechanisms for charging the battery. It also does the same when the battery shows empty. In SAVE or when showing empty, it charges till it adds roughly 1 mile (2km) of range, then it goes back to EV till the range has dropped to the original level. CHRG simply charges till you tell it to stop by turning it off. So running CHRG on a flat road till the battery is 75% full and then using EV (immediately, or in town after a while using SAVE) actually uses a tiny bit less fuel according to experiments by some Aussie users, but the difference is so small as to be lost in the possible errors.

So what I do is use SAVE as soon as I hit the highway, and turn it off when travelling slowly (no 'EV' on my pre-facelift model). If my battery is way below 75% and I know I've got a long stretch of EV driving (such as when dropping my daughter off in central London), I'll use CHRG on the highway to top it up to 75% before hitting the urban roads.

I'm still tinkering with using CHRG on the longer downhill stretches of highway as the ICE can charge the battery much more quickly when the motors use less power. I then press to SAVE once the road levels out.

 

[quenthal]

Both SAVE and CHRG use exactly the same mechanisms for charging the battery. It also does the same when the battery shows empty. In SAVE or when showing empty, it charges till it adds roughly 1 mile (2km) of range, then it goes back to EV till the range has dropped to the original level. CHRG simply charges till you tell it to stop by turning it off. So running CHRG on a flat road till the battery is 75% full and then using EV (immediately, or in town after a while using SAVE) actually uses a tiny bit less fuel according to experiments by some Aussie users, but the difference is so small as to be lost in the possible errors.

So what I do is use SAVE as soon as I hit the highway, and turn it off when travelling slowly (no 'EV' on my pre-facelift model). If my battery is way below 75% and I know I've got a long stretch of EV driving (such as when dropping my daughter off in central London), I'll use CHRG on the highway to top it up to 75% before hitting the urban roads.

I'm still tinkering with using CHRG on the longer downhill stretches of highway as the ICE can charge the battery much more quickly when the motors use less power. I then press to SAVE once the road levels out.

Thanks, I'll have try these ideas out!