Kundalini
Posts: 11
Joined: Tue Jan 05, 2016 2:22 pm
Location: Bonnie Scotland

Re: BMW UK i3 REx without plugging in?

Mon Jan 18, 2016 7:05 am

psquare, if that's not an advert for petrol driven lawnmowers then i don't know what is.
Try watching it more intently (in the nicest possible way).
I know which one i'd prefer to use if i was a professional gardener.

Using my 700 Watt, corded electric hedge trimmer, i can complete my surrounding 6 foot high privet hedges in around two hours, whereas when i borrowed my neighbours 22cc/650W petrol cutter, it took me half the time (made a much better job too).
Rechargeable Li-Ion trimmers are the worst performers of the lot, going by all accounts.

Considering any extra electricity used here will soon be produced by way of fracking (ENVIRONMENTAL DISASTER), petrol will become the new "green" fuel.

Please don't get me wrong i love almost everything about the i3 and know it's super efficient and perfect for town and city driving but i do worry that its high electricity requirement may not be best for this nation of ours.

psquare
Posts: 481
Joined: Wed Oct 15, 2014 5:57 am
Location: i3 REx, 225xe Hybrid UK
Contact: Website

Re: BMW UK i3 REx without plugging in?

Mon Jan 18, 2016 7:57 am

Kundalini wrote:psquare, if that's not an advert for petrol driven lawnmowers then i don't know what is.


Excellent observation. Despite RL being sponsored by Bosch: one can prove anything with facts on efficiencies, right?

Kundalini wrote:I know which one i'd prefer to use if i was a professional gardener.


But you're not, aren't you? That's why electric lawn mowers are designed to cut lawns for the average Joe.

Kundalini wrote:Using my 700 Watt, corded electric hedge trimmer, i can complete my surrounding 6 foot high privet hedges in around two hours, whereas when i borrowed my neighbours 22cc/650W petrol cutter, it took me half the time (made a much better job too).
Rechargeable Li-Ion trimmers are the worst performers of the lot, going by all accounts.


You're getting your hedges and your lawn all muddled up. It's about the right tool for the job. Of course I also prefer a petrol chainsaw to chop a tree branch over an electric model. But how often do I chop a tree? And how often do I mow my lawn? You get the picture.

Kundalini wrote:Considering any extra electricity used here will soon be produced by way of fracking (ENVIRONMENTAL DISASTER), petrol will become the new "green" fuel.


Well, I can't argue with industry expert insights such as this.

Kundalini wrote:Please don't get me wrong i love almost everything about the i3 and know it's super efficient and perfect for town and city driving but i do worry that its high electricity requirement may not be best for this nation of ours.


Ok, you love burning (green) petrol and therefore bought an electric car. As long as that makes sense to you, that's all that matters.

Kundalini
Posts: 11
Joined: Tue Jan 05, 2016 2:22 pm
Location: Bonnie Scotland

Re: BMW UK i3 REx without plugging in?

Mon Jan 18, 2016 8:58 am

Cheeky Fool

jadnashuanh
Posts: 3283
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: BMW UK i3 REx without plugging in?

Mon Jan 18, 2016 12:51 pm

Kundalini wrote:Now, when you consider the REx petrol engine is capable of producing 25 Kw then, without restrictions, it could charge the battery pack from 1/2 empty to full in just 23 minutes (disregarding losses and warm up time).
Thats a Rapid Charging station in the boot.

While 34Hp does equal a bit over 25Kwhrs, do you really believe that the REx is 100% efficient! Far from it! There is a fair amount lost in heat and friction not counting losses in the conversion process of the generator. Burning fossil fuels in a small engine is not particularly efficient.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

i3Alan
Posts: 232
Joined: Wed Jul 09, 2014 4:08 pm

Re: BMW UK i3 REx without plugging in?

Mon Jan 18, 2016 6:39 pm

jadnashuanh wrote:
Kundalini wrote:Now, when you consider the REx petrol engine is capable of producing 25 Kw then, without restrictions, it could charge the battery pack from 1/2 empty to full in just 23 minutes (disregarding losses and warm up time).
Thats a Rapid Charging station in the boot.

While 34Hp does equal a bit over 25Kwhrs, do you really believe that the REx is 100% efficient! Far from it! There is a fair amount lost in heat and friction not counting losses in the conversion process of the generator. Burning fossil fuels in a small engine is not particularly efficient.

Note that 23 minutes at 75 MPH is 28.75 miles. When I travel almost 30 miles at 75 MPH, I will use almost half my charge. So, the efficiency going from the 34HP engine to the battery is not too bad.

The biggest inefficiency of the REX is going from the energy content of the gasoline to the 34HP output. That is under 40% efficient. Going from the 34HP output to the battery is likely over 85%, including losses in both the engine's generator and the battery charge efficiency.

Kundalini
Posts: 11
Joined: Tue Jan 05, 2016 2:22 pm
Location: Bonnie Scotland

Re: BMW UK i3 REx without plugging in?

Tue Jan 19, 2016 7:06 am

The petrol power plant in the REx is the same 647cc two-cylinder engine used in the BMW C650 GT maxi-scooter where it produces 44 kW (60 bhp) at a dizzy 7,500 rpm but would be too powerful and unbearably noisy in that guise.
I expect BMW have de-tuned it for maximum possible "efficiency" (a balance of least petrol used with power output best suiting battery charging coupled with least noise) for this application.

The 25kW output is just that, friction and heat don't reduce it, with any heat produced (some by friction) being an added bonus which isn't wasted and can be efficiently utilised in other ways.

I could be wrong so don't quote me, but wouldn't the battery charging power delivered by the engine via the generator already be DC therefore eliminating the need to inefficiently convert from AC as happens when plugging in (unless you paid extra for the rapid DC charging option)?
BMW are sometimes accused of making exaggerated claims regarding range and charging times; similarly (although difficult to prove) the electrical output at charging points is probably seldom constant or accurate, so yet more inefficiencies.

Anyway, nitpicking over small gains and losses seems unimportant when a major, calamitous, underground gas leak (broken well) in Aliso Canyon, California has been spewing out around 72 million cubic feet of methane into the atmosphere every day for months now (roughly equivalent to the emissions from about 4 1/2 million cars) and they don't expect to stem the flow until Feb/March..... which likely means June.

Another fine mess.

nowtta60
Posts: 182
Joined: Sun Aug 03, 2014 10:15 am
Location: Staffordshire, UK

Re: BMW UK i3 REx without plugging in?

Wed Jan 20, 2016 5:26 pm

Kundalini wrote:Any significant rise in demand on the National Grid due to the rapidly increasing number of electric plug-ins, only increases the use of "dirty" fossil fuels to balance supply.
Thanks, Peter

You do realise with those dirty fossil fuels that an i3 powere by just coal fired electricity is still lower on CO2 in the life cycle than a diesel / petrol powered car.
At 800g/kWh for coal (which includes for minining, trasnportation and not just the burning)
i3 gets about 4 miles per kWh.
So 200g/mile
Or about 125g/km. All life cycle emissions included.

A 125g/km ICE only gets about 75% of its official mpg figures, which has the same effect on emissions.
So 125g/km for an ICE becomes 166g/km.
And thats just foe the fuel burned by the car, not drilling, pumping, refining, shipping, and forecourt pumping usage which is included in the coal figure.

Hoever the grid isn't all coal powered - and will be zero coal in 10 years as the government announed plans to shut down all coal plant within 10 years. Current grid emissions which should be used for a fair comparison are 350g/kWh. So an i3 on grid elecrtic is
350/4/1.6 = 54g/km.
OR go to Ecotricity or Good Energy and get 0g/km.

Lastly - 50,000 people a year are killed in the UK by the effect of air pollution from transport. Moving the emmssions from exhaust pipes to powerstations is much better than using city air as a sewer. NOX and CO and SO2 and PMs. These are much more highly regulated and controllable when emitted from centralised sources like coal or CCGT powerstations. Flue gas de-suplhursation, SCR NOx scrubbers, electrostatic particulate filters etc.

Then we come to the fact that 97% EVs are charged at home at night. On a grid which currently has 20GW of space capacity overnight. Or enough to provide 2/3 of the dfaily driving demand of the whole UK car fleet. (120GWh per night over 6 hours). EVs make the grid by more efficient - by not having powerstations slowing down from and coming up to generation temperature, which means burning fuel with no power generation.

For the future we'll also have smart grid capabilty so EVs can be switched on and off from charing to balance the minute to minute national needs.

In short... Don't spread myths created by the oil industry! ;-)
i3 REX Ordered 06/08/14. Collected 27/01/15
Capparis White, 429s, Loft, Park Assist, Winter Pack, Professional Media, Drive Assist Plus, DC Prep, LED headlamps.
Essential energy reading for EV owners... http://www.withouthotair.com/

nowtta60
Posts: 182
Joined: Sun Aug 03, 2014 10:15 am
Location: Staffordshire, UK

Re: BMW UK i3 REx without plugging in?

Wed Jan 20, 2016 5:40 pm

Kundalini wrote:Oh dear........ Thanks for the replies guys.

Currently, plugging in at home would require the cable to cross a public pavement which wouldn't be allowed.
The nearest "fast" charge station would be the BMW dealership (9 very slow/ heavily congested miles away).
I do live opposite a petrol station though (typical).

I had originally thought the small 2 cylinder petrol engine in the UK spec i3 REx could only be used to maintain battery charge state, not increase it (although how they worked that one out whilst combining it with battery charge increasing regenerative power I'll never know).
If I was wrong then, problem solved.
Charge the battery pack to max with the engine then drive on near silent electron power till i next need to use my onboard generator to charge up.

RESULT !!!

Thanks again guys,
Peter

Who says its not allowed? Threre's a few people on speak EV forum who've stuck an EVSE pod at the edge of their property and then use an anti trip mat to stick the cable under while charging. It's debatable whether its legal and you won't get grant funding at all, but at least you can fully charge an i3 in under 4 hours.

The other option is to see if the council will apply for the 75% grant to stick in a public charger in a location near to you. They might have issue with the other 25%, but I'm working on a solution to that with a bunch of other EV owners. Trying to set up a community owned charging network. Lots left to sort out, but it looks feasible.
i3 REX Ordered 06/08/14. Collected 27/01/15
Capparis White, 429s, Loft, Park Assist, Winter Pack, Professional Media, Drive Assist Plus, DC Prep, LED headlamps.
Essential energy reading for EV owners... http://www.withouthotair.com/

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