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Hybrid MPG


PAISLEY1903
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Just ran my Battery down on a long run home and decided it was a good time to try a petrol run. So I drove the 5 miles downhill to my local Coop and 5 miles back uphill and I admit to being light of right foot but not crawling - 56mpg. I was hoping for 40 plus.

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My car was a demonstrator and I bought it at 5months old (end of 2019) when I reset mpg and I haven’t touched it since and at the moments it stands at 54.6. I do mainly longer runs on motorways and A roads and don’t use it much locally in London although a hybrid can be quite good mpg wise on short traffic runs when it runs more on electric.. mine is a 4wd excel. I think the 4wd can be more economical than the 2wd because you have an extra motor/generator that puts twice as much charge into the traction Battery so more power to drive on electric only.

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If we are talking about fwd version self charging hybrid versus awd self charging hybrid I believe the fwd will be more economical in all situations. The rear axle mg can indeed produce more power while regenerative braking is activated however self charging hybrid has small Battery that is topped up quickly and then no more power can be stored. The plug in hybrids can benefit from long downhill and a lots of regen energy. 🔋👍

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Cyker, if my dealer picks the car up their mpg to and from the garage is sub 50 compared to my 70+ for the same journey. 

Not been able to work out why 😂

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On 8/17/2022 at 2:04 PM, TonyHSD said:

however self charging hybrid has small battery that is topped up quickly and then no more power can be stored. The plug in hybrids can benefit from long downhill and a lots of regen energy.

While this is perfectly true in theory, I suspect that it rather less significant in practice ...

It is safe to assume that by the time you have got a HEV to the top of a big hill the traction Battery will be pretty much exhausted - meaning that you have capacity to store between 1 kWh and 1.5 kWh. An 'empty' PHEV Battery would have ample capacity to store between 10 kWh and 15 kWh - so ten times the capacity. So, if you had a sufficiently long "inclined plane" you could recover around ten times as much energy with a PHEV as you could with a HEV.

Translating this into the real world with numbers ... the objective here is to recover the potential energy gained from being at the top of a hill by rolling down using the electric motors as generators. The available energy is given by: U = mgh where m is the mass of the vehicle, g is the force of gravity and h is the height of the hill. Given that the Rav4 is around 2000 kg and the force of gravity is 9.8 m/s^2 we can potentially recover 19.6 kJ per metre of descent.

Since 1 Wh = 3.6 kJ, this means that we can potentially recover 5.44 Wh per metre of descent.

Now we just need to find a long hill ... 🙂 ... "Cragg Vale from Mytholmroyd on the B6138 road proudly claims to be the longest continual ascent in England. 968 feet of climbing in 5.5 miles." 968 feet is 300 metres between friends, so in rolling down Cragg Vale we could potentially recover 1.633 kWh and, while that wouldn't fit into the HEV Battery, the recovery process is unlikely to be better than 50% efficient so the 0.8 kWh recovered comfortably would - having a larger PHEV battery wouldn't be of any benefit at all. And most UK descents are going to be well under the 300 metre mark.

So, in practice, I suspect that Toyota have sized the traction battery in the HEV quite sensibly ... 😉

(If I've got my physics or arithmetic wrong please do 'yell' - I think I've got it correct ... 🤞)

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1 hour ago, philip42h said:

While this is perfectly true in theory, I suspect that it rather less significant in practice ...

It is safe to assume that by the time you have got a HEV to the top of a big hill the traction battery will be pretty much exhausted - meaning that you have capacity to store between 1 kWh and 1.5 kWh. An 'empty' PHEV battery would have ample capacity to store between 10 kWh and 15 kWh - so ten times the capacity. So, if you had a sufficiently long "inclined plane" you could recover around ten times as much energy with a PHEV as you could with a HEV.

Translating this into the real world with numbers ... the objective here is to recover the potential energy gained from being at the top of a hill by rolling down using the electric motors as generators. The available energy is given by: U = mgh where m is the mass of the vehicle, g is the force of gravity and h is the height of the hill. Given that the RAV4 is around 2000 kg and the force of gravity is 9.8 m/s^2 we can potentially recover 19.6 kJ per metre of descent.

Since 1 Wh = 3.6 kJ, this means that we can potentially recover 5.44 Wh per metre of descent.

Now we just need to find a long hill ... 🙂 ... "Cragg Vale from Mytholmroyd on the B6138 road proudly claims to be the longest continual ascent in England. 968 feet of climbing in 5.5 miles." 968 feet is 300 metres between friends, so in rolling down Cragg Vale we could potentially recover 1.633 kWh and, while that wouldn't fit into the HEV battery, the recovery process is unlikely to be better than 50% efficient so the 0.8 kWh recovered comfortably would - having a larger PHEV battery wouldn't be of any benefit at all. And most UK descents are going to be well under the 300 metre mark.

So, in practice, I suspect that Toyota have sized the traction battery in the HEV quite sensibly ... 😉

(If I've got my physics or arithmetic wrong please do 'yell' - I think I've got it correct ... 🤞)

That’s an interesting read, thank you 👌

I have no idea how much can phev top up Battery but my Auris has small 1.3kw/h Battery and I have it topped up every day on the way home. It’s a downhill 8% gradient for about a mile and before that it’s slight gradient down and I mostly go on ev, speed limit is 40mph but I do probably a bit lower , sometimes a bit over which will be true 40mph. My Battery is often full at the bottom and the engine is screaming at super high rpm, forcing the car to switch to ev to complete my final few hundred yards home and I get message ev mode not available, but I keep trying and eventually the car accepts it and then I drive in ev uphill a bit but battery is so full (80% measured with app)  that remains full. I have my battery very easy topped up full, plus I do a lot of motorway trips which also helps. If I had Rav4 or Prius phev I wonder how much more I can benefit from my driving style and if this will increase efficiency. 

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I purchased a dynamic all wheel drive 2021 plate average 45 mpg, ev mode OK for around town use but very limited. Previously I had a prius a 2018 plate 68 Ave mpg. It's horses for courses heavier car bigger engine.

However I wouldn't go back to my prius, the comfort visibility,  road clearance is worth it, my main reason being the deteriorating  roads in the UK and the ability to ride out the bumps and dips in our crumbling roads

 

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My FWD HEV is now nearly 2 months old & the onboard average mpg reached 54.2 over 1200 miles, which is very close to my actual brim to brim calculations. Yesterday we did a 400 mile round trip to Manchester, mainly fast motorway driving not thinking of fuel economy. Very pleased to say the average mpg only dropped 1.0 by the time we arrived home. Therefore, average onboard mpg now 53.2 after 1600 miles.

While I had been concerned by the seat comfort & driving position for long journeys, I needn't have been - excellent!

Next test for the Rav4 is as golfing transport, carrying 2 or 3 golfers with their bags, trollies etc.

 

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I have a 20plate Icon which has covered 22k miles and currently my average for all those miles is 50.5mpg

Only ever use Sainsbury's E10 fuel and i'm pretty happy with the MPG. Recently i've changed customer with work so have seen much higher MPG, due to zero motorways and lots of A road muching, where EV is used over 50% of the time on every journey.

Below is the tracked MPG per fill up, for the life of the car.

image.thumb.png.13a39b155fe7dec8bc09dc1c91dfda17.png

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  • 4 weeks later...

We took our 2021 Rav4 down to Droitwich Spa, from Cairnryan, looked at various local sights and attractions over the course of a week, and drove back.

Prior to this trip our local summertime mpg had a high of 57(based on a couple of longer liesurly jaunts) but dropped back to a more realistic 55. This based on never re-setting the fuel data. Except late in the spring to cancel the poorer(say 45 mpg) winter consumption figs.

Anyway with 660 miles there, and back, on "A" class and M Ways, with the cruise control set for an indicated 65 or 75(and adjusted for temporary local 50/55 M' Way speed limits)

Over some 1050 miles in total we got 54.7 mpg.

Cheers,

Marcus

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These are the stats for a very restrained trip from the Midlands to Essex in my PHEV. I used ACC on dual carriageways and Mways set at 65. Two people up plus luggage.

 

Screenshot_20220926-200440.png

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6 minutes ago, Hayzee said:

These are the stats for a very restrained trip from the Midlands to Essex in my PHEV. I used ACC on dual carriageways and Mways set at 65. Two people up plus luggage.

 

Screenshot_20220926-200440.png

My last trip very similar, also two up plus luggage etc.

 

0177A994-1476-4666-9FDD-A428533A090C.jpeg

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10 hours ago, Hayzee said:

Ernie.....was that trip in HEV mode all the way?

Yes and no, I always start and deplete the EV mode and let it switch into HEV automatically. I've found this the best option for me.

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I have a 21 Excel HEV AWD. I've got a lifetime mpg of 51, tends to be about 54 summer and 47 winter. I use the cheapest petrol I can find and I've never noticed any difference between brands or grades of fuel. Mostly rural B roads and maybe 25% motorway where I use cruise set at 75 where possible. (Roughly 70 on GPS)

 

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