Maintaining SOC while towing a caravan / under heavy load

[anko]

Difference in fuel consumption / power output when coasting in B2 (first two dips in speed result in huge drop of consumption / output):

Next picture shows how engine output reduces over time slightly, as SOC increases:

 

[gwatpe]

I have also noticed a particular problem with the car seeming to run away on slight downhill stretches with the foot off the gas. Not a particularly good feature to have acceleration when the foot is taken off the gas. Happened with series and parallel hybrid modes, in the 70-110km speed range.

I would think any car I have ever owned would run away on a downhill stretch, unless I engaged CC.

This cannot be so.

My last car, was an Auto, a NISSAN MAXIMA V6 3L, and this car would slow on a slight downhill grade, in drive. Another Previous car was a HONDA PRELUDE 4WS 2.0L MANUAL. This would certainly slow, with engine breaking when the foot was taken off the gas. Maybe if the car was placed in neutral. :roll:

The road was not what I would consider a hill of any sort. Maybe a 1:100 or less grade. I will check with normal use of B0.

 

[anko]

You are right. If the angle was so small, that internal resistance of the engine together with other frictional forces and air resistance was greater than the forward vector in the gravitational force, then a normal car would possibly hold its pace or even slow down. But if the angle increases a bit it will speed up, unless you purposely shift down (Will an Auto do that by it self? I doubt that). The same applies to our car.

One difference: our car was designed to have 0 (disengage and turn off engine) or very little resistance from the engine to allow for coasting as much as possible. So, our car wil start to speed up on at smaller angle that a normal car would do. But to call this dangerous? IMHO it is the same as saying it is dangerous that it doesn't slow down as fast as a normal car when you take your foot of the throttle when aproaching a red traffic light.

 

[RobOwen]

... our car was designed to have 0 (disengage and turn off engine) or very little resistance from the engine to allow for coasting as much as possible. So, our car wil start to speed up on at smaller angle that a normal car would do.

I had the same arrangement as standard on my last VW Passat Alltrack & previous Tiguan. To re-introduce "engine braking" I could either dab the footbrake lightly, select a manual gear with the DSG gear selecter or disable the "coasting" function in the OBD menu. With the Mitzy, selecting B0 for coasting and then using the steering wheel paddles to increase regenerative braking as and when required is simpler, to my mind.

 

[gwatpe]

Anko raised a way of allowing the petrol engine to provide additional generator power to allow the battery to attain a higher battery %SOC faster. Using the paddles changes the car computer algorithms and reduces the the generator output by changing the settings. Sort of defeats the point. The brake affects the generator differently and it seems that the accelerator has to be pressed to increase the power levels again, by someway resetting the power levels.

The benefits of this are subjective, and until there is some way, independent verification of objective measured data is available to drivers, there will continue to be conjecture.

The sequence can rapidly give an increase in battery %SOC if driving conditions allow.

The default setting is B2, so MMC made this close to a normal car behaviour. The process of Reverting to B0 after cancelling the cruise control to initiate the process to put more energy to the battery will probably require a lot of driver input with buttons and paddles, unless the road conditions are good, and there is minimal traffic, to allow an uninterrupted sequence.

A mate is testing this procedure while towing a caravan with his PHEV across outback Australia and am yet to hear back how it is working.

 

[Titan]

As a point of interest, what do the car's infographics show during this coasting / B0 / accelerate/recharge initiation phase? Will it show nothing on cancellation of CC until the accelerator is pressed, at which point it starts showing blue arrow to the battery, or something else? I only ask because it would be easier watching that than having to plug in an OBD2 took to check charge. Presumably the car should be telling correctly what is happening.

 

[gwatpe]

The graphics on the dash do show the blue arrow from petrol engine to battery. Without the instant petrol consumption data, the driver would not know there was any difference. Without an instant generator power number to see and only the increased petrol consumption we have to believe the increased bars in the battery gauge correspond to equivalent conversion to electricity minus losses.

The new OBD2 HUD I have ordered, and is still coming. here is a link. Does not have any battery info, but is still useful for general driving.

http://www.ebay.com.au/itm/391041295584?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

If I get a i909 test unit, I will likely make a data viewing program with VB6 so I am able to view multiple data on the same time stamps for comparisons. I am not that keen on computer strip charts, and it brings back memories of my working days.

 

[Titan]

The graphics on the dash do show the blue arrow from petrol engine to battery. Without the instant petrol consumption data, the driver would not know there was any difference. Without an instant generator power number to see and only the increased petrol consumption we have to believe the increased bars in the battery gauge correspond to equivalent conversion to electricity minus losses.

Well that kind of sucks. Think I might have to get my obd2 unit of the shelf and have a look myself.

 

[gwatpe]

I have been testing multiple ways of replacing battery %SOC on trips where corded recharging is unavailable.

It seems that the PHEV may be considered under powered for any extended towing trip. The main difference between the PHEV and a traditional powered vehicle is related to the impact on towing that a depleted battery has. A normal vehicle with gears, power can be adapted to suit, without any residual impact on future power availability. The PHEV can suffer power loss when the battery is depleted.

I have not had the opportunity to tow, but have tested recharging a fully depleted battery to full on 2 successive drives in a day. The drives were each approx 450-500km on flat terrain on the same day. Australia is quite flat in many places. My PHEV was tested with cruise control set at 110kph on one run and 100kph on a second. Both tests, had the battery fully recharged in about 150km in CHARGE mode. The PHEV was loaded with approx 300kg of luggage, and 2 passengers. No roof box or bars. At the start of the test, the petrol consumption was about 10.5L/100km and the car replaced battery range 1km for each 2km driven. At about 8bars, the petrol consumption decreased and the number of km to gain a 1km in battery range increased. The last bar from 15-16 bars did take about 15km. At the end of the test, the petrol consumption was very close to the normal average for the speed. My PHEV averages about 7L/100km at 100kph and 8L/100km at 110kph. The tests although not very extensive, highlight the good optimization of the PHEV to load the ICE and efficiently convert petrol energy to stored electrical energy for later use. There was no benefit in economy to say drain the battery by running in EV mode and then recharging, and repeating this on a longer trip. Just us SAVE mode and not deep cycle the battery.

I have tried to use "anko" method as well, but cruise control is not available, so there is potential for speed variability that make interpretation of any measurements difficult.

At low battery %SOC, at 100-110kph, the PHEV has approx 50% more power available, as it can store 1km for every 2km driven. If the vehicle load results in an average petrol consumption of over 10L/100km, I would expect that the battery %SOC will fall until some power limiting may occur. Short periods of reduced driving speeds may allow enough power to be stored to continue at a higher speed until the process needs to be repeated.

This may help other PHEV owners work out a better driving strategy while towing.

 

[greendwarf]

There was no benefit in economy to say drain the battery by running in EV mode and then recharging, and repeating this on a longer trip. Just us SAVE mode and not deep cycle the battery.

But there might be if the longer trip involved more than one stretch of high speed running alternating with low speed/urban driving. I did this yesterday where I used about half the battery driving out of London then used Save until I got to Dartford Crossing (very slow when they closed on of the bores, with vehicles in it ) then back to Save on the other side until Southend. Then apart from a quick 1 hours top-up at a Fast charger, whilst shopping, I used up the rest of the battery driving around Southend.

As I had to negotiate the Dartford Crossing again on the return journey and don't like using petrol once in London, I put it into Charge once I got to 50mph until I got to the Services at Dartford, where I topped it up with a Rapid charger (just finished when a Leaf arrived :lol: ). Then it was back to Save until hitting the 30pmh limit on the edge of Town and EV to home. Only "down side" is that I had 7 miles of relatively expensive petrol generated energy left rather than zero.

 

[anko]

I have been testing multiple ways of replacing battery %SOC on trips where corded recharging is unavailable..

Thanks for the heads up.

It seems that the PHEV may be considered under powered for any extended towing trip. The main difference between the PHEV and a traditional powered vehicle is related to the impact on towing that a depleted battery has. A normal vehicle with gears, power can be adapted to suit, without any residual impact on future power availability. The PHEV can suffer power loss when the battery is depleted.

I don’t think it is underpowered. I think it is lazy. With “seems underpowered” as a result. When driving conditions require such, fuel consumption can easily go up to 15 liter / 100 km or more. But when driving conditions are easy, fuel consumption will drop to 11 l / 100 km or even less (when coasting). So, when driving is easy, instead of preparing for the future by building up SOC, the engine kinda settles down. I am more or less convinced that if consumption would stay at 12 or maybe 13 l / 100 km, the car would easily maintain SOC at a high enough level to deal with whatever conditions you will encounter on a ‘normal’ extended towing trip.

Because you are able to maintain higher SOC, you will prevent (all or most of) the high revving of .the engine and have some SOC left at the end of the trip for some EV driving. So, I don't think overall average consumption would be affected. Unless this triggers you to drive faster, of course :mrgreen:

BTW: I think the car will suffer from power reduction, rather than power loss

I have tried to use "anko" method as well, but cruise control is not available, so there is potential for speed variability that make interpretation of any measurements difficult.

Using this technique, this weekend I actually managed to enhance my SOC while towing my caravan on the motorway. Did I increase it’s power? No, I made it less lazy. Does it make a difference whether it is underpowered or lazy? Well, one is more easy to resolve then the other.

When towing, there is a 'zone', in which you only see the orange arrow from engine to wheels. Apparently no power going to the batteries and no power coming from the batteries. While towing a caravan on a flat road, you will spent most of the time in that zone. Unfortunately, as the BMU will tell you, a constant 9 - 12 A mps (3 - 4 kW) are being discharged from the battery. This power is fed into the E-motrors (1005 sure) as well as the generator (99.9% sure) to prevent them from dragging. At the cost of a little extra fuel, this power could be generated by the generator and fed into the motors, leaving SOC untouched. And another little bit of extra fuel would allow the SOC to actually increase.

Funny enough, I don't think average speed while towing has much impact on the ability to maintain SOC. Once you are driving fast enough to stop the charging process (and let's assume at motorway speeds you are), you can still gradually speed up (at a cost of higher fuel consumption) without taking power from the battery. Although I would not advise it, you could "pulse and glide" (as Prius owners call it) in B0 to allow the engine to generate some extra SOC during the glide phase. Then it shouldn't matter whether you pulse to 100 km/h and glide to 90 or pulse to 110 and glide to 100. As long as you don't pulse so hard that it requires power from the battery. During the Glide phase, about 76 Amps (25 kW) is fed into the batteries. Unfortunately but understandably, at higher SOC's this will be less. So maintaining SOC becomes easier when SOC is lower. Still get it?

 

[maby]

...
I don’t think it is underpowered. I think it is lazy. With “seems underpowered” as a result. When driving conditions require such, fuel consumption can easily go up to 15 liter / 100 km or more. But when driving conditions are easy, fuel consumption will drop to 11 l / 100 km or even less (when coasting). So, when driving is easy, instead of preparing for the future by building up SOC, the engine kinda settles down. I am more or less convinced that if consumption would stay at 12 or maybe 13 l / 100 km, the car would easily maintain SOC at a high enough level to deal with whatever conditions you will encounter on a ‘normal’ extended towing trip.
...

With the battery and petrol engine working together, it's not underpowered - in fact it is quite a fast car for its size and design. The trouble is that it is too willing to let the battery deplete - and quite slow to recharge it. This is where we need the "I'm not going to be recharging for several days" mode.

 

[anko]

This is where we need the "I'm not going to be recharging for several days" mode.

In the context of this topic, I don't think it has anything to do with recharging or not, but what would that mode be like, in your opinion?

 

[Grigou]

This is where we need the "I'm not going to be recharging for several days" mode.

In the context of this topic, I don't think it has anything to do with recharging or not, but what would that mode be like, in your opinion?

It does exist : Charge mode !

 

[anko]

Hmmm, this topic was created to discuss the 'issue' that Charge mode will not allow you to maintain SOC while towing or under heavy load. Your solution must be a solution to some other issue.

 

[Grigou]

Sorry, I had already forgotten your first post on this topic

 

[anko]

Yeah, topics tend to drift ...

 

[Angelfire]

As a retired HGV driver and long time caravan owner there is no doubt in my mind that I would not have chosen an EV hybrid for towing. Give me diesel for pulling power every time. I also believe that the Outlander PHEV is the only vehicle manufactured on the market that will tow a trailer/caravan. Must be a reason for such why other manufacturers say towing is a no no.

Angel.

 

[anko]

Must be a reason for such why other manufacturers say towing is a no no.

Such as Volkswagen and Volvo? Wakeup time

 

[ShaunHicks]

When you are concerned with overloading the engine: Max output is not affected. Overal average output is not affected either. There will less periods of serial mode (so less engine racing). As a plus, the engine runs at a higher load and thus a higher efficiency. I think fuel consumption may actually go down, as you might actually end up in EV mode at some point.
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