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

BMW UK i3 REx without plugging in?

Tue Jan 05, 2016 2:28 pm

BMW i3 question

Hi all, new UK member here but have perused the site often as a guest.
My daily travel (5 days) consists of a relatively flat 5 miles averaging about 40mph* then a steep climb up over the Campsie fells which is a rise of approx 500m in 2.5 miles to the top and the same down the twisty other side with a further 5 miles of flat terrain to destination. My return journey is the same in reverse (not gear for the jokers).
Having gone through many sets of brake pads over the years, i acknowledge and bemoan the wasted energy going downhill whilst braking.
I've been weighing up the merits of the electric BMW i3 with range extender (plugging in the pure electric version every other night may become irksome when the novelty wears off, not to mention the prospect of getting stuck on top of a snowy mountain road in winter with a low battery level and no phone signal)
Theory is If i started the REx at say 75% battery level all the way up to the top of the fells then switch off and top-up the battery with regenerative energy from the steep descent.
My question is this:
Would it be possible to reach anywhere near 100% state of battery charge with regenerated electricity during descent, meaning no plug-in required "EVER"?
I suspect it's a lot more complicated than described but it would be my ideal situation.
Any comments or views from you knowledgable guys might sway me towards an i3 REx.


Thank you,
Peter

Edit: * Just noticed Where i said i averaged 40mph i meant a maximum of about 40mph, the average being closer to 15mph.
Last edited by Kundalini on Thu Jan 07, 2016 7:00 am, edited 1 time in total.

Jeffj
Posts: 252
Joined: Mon Sep 15, 2014 12:32 pm
Location: Boulder, CO

Re: BMW UK i3 REx without plugging in?

Tue Jan 05, 2016 3:23 pm

You can certainly increase the charge level of the i3 by descending and engaging the regenerative brake to capture the energy. However, nothing is 100% efficient, so you will use more energy to climb the hill that you will re-capture descending. I've descended 6,000+ ft. across ~20 miles with my i3 and (coupled with running the REx) have been able to go from ~30% SOC to 75% SOC.

I'd guess, however, from your description, that you wouldn't really gain more than a couple of percentage points on your SOC with the descent.

Why do you think plugging it in "every 2 days or so" would be a problem? It takes maybe 5 seconds to plug in the car, and about the same to unplug it, unless you have a really tortuous process for getting power out to your car.

jadnashuanh
Posts: 3453
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: BMW UK i3 REx without plugging in?

Tue Jan 05, 2016 3:53 pm

You certainly would minimize your brake pad wear with any EV, especially with the i3 if driven properly. Plugging in is not a big deal, but maybe bigger in the UK where you'd have to coil and uncoil the cord each time. The EVSE's in the USA have a cable tethered to the EVSE, but that is not the case in Europe. Still, it should not take much more than a minute. Not knowing the total distance of your typical trip, you might find that the BEV would work for you as well. The car does not use much power when it is not moving, and the REx is less efficient, especially at heating than the BEV (the BEV has a heat pump (standard in the USA, not sure about Europe) while the REx must rely on electrical resistance heating, which is much less efficient). Plus, the REx, being heavier, creates a hit on efficiency. Now, having the REx may mean you might get by with it as your only vehicle, and you have to consider that as well. It wouldn't suffice for my driving needs, but might for yours, which is why I bought the BEV verses the REx...we have few CCS charging units where I live, and my typical trip would be an annoyance trying to use the REx on petrol most of the way.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

MikeS
Posts: 698
Joined: Thu Jan 16, 2014 8:29 am
Location: Brighton UK

Re: BMW UK i3 REx without plugging in?

Wed Jan 06, 2016 12:09 am

“Plugging in is not a big deal, but maybe bigger in the UK where you'd have to coil and uncoil the cord each time. The EVSE’s in the USA have a cable tethered to the EVSE, but that is not the case in Europe.” This is true for public EVSEs where in UK we use our own cable. However, on my EVSE at home the cable is part of the EVSE so all I do when I charge is pick up the plug, remove the cap on the car and plug in. In reality, no more time consuming than plugging in my phone!
BMW 3 Series 2005 - Aug 2014
BMW Z4 35i 2009 - Mar 2014
BMW X1 Mar 14
BMW i3 Sep 14

janner
Posts: 230
Joined: Sun Jan 25, 2015 5:24 am
Location: Bath, UK

Re: BMW UK i3 REx without plugging in?

Wed Jan 06, 2016 12:50 am

You should think of the ReX as a BeV with 40kWhrs of energy storage and not as a car with a small engine. If you want to use the car for journeys other than your commute then get a ReX otherwise BEV and a home charger.

In the UK lots of home EV Chargers have tethered cables. It's only at public level 2 charging points that we need our own cable. Plugging in is not a problem if you do it at home. Don't think about an electric car if you can't charge at home.

Under most conditions 75% charge will be reached after 15 - 20 miles so you probably won't have reached this until you get to work. On the way back you might gain from being able to turn on the ReX but you shouldn't need to. If you count your 2.5 miles up and 2.5 miles down as say 10 miles flat then you one-way journey is 20 miles equivalent. You should be able to get there and back with lots to spare.
2015 i3 ReX Solar Orange, Loft interior world. BMW professional, 19" turbine-spoke 429 wheels, DC rapid charging, driving assistant plus.

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

Re: BMW UK i3 REx without plugging in?

Wed Jan 06, 2016 6:34 pm

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

jadnashuanh
Posts: 3453
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: BMW UK i3 REx without plugging in?

Wed Jan 06, 2016 8:44 pm

There are limits on how much the REx can increase the charge state of the batteries and WILL NOT recharge it to full capacity...it will shut off way before that happens, either from running out of fuel or from the computer. In normal practice, you can't turn the REx on manually until the SOC has dropped below 75%, and whatever level you engage it, that is the maximum it will try to maintain.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

psquare
Posts: 483
Joined: Wed Oct 15, 2014 5:57 am
Location: i3 REx, 225xe Hybrid UK
Contact: Website

Re: BMW UK i3 REx without plugging in?

Thu Jan 07, 2016 4:38 am

Kundalini wrote: Currently, plugging in at home would require the cable to cross a public pavement which wouldn't be allowed.


What about renting a garage or place to park nearby, which might come with a power socket? Not being able to charge at home and using hills/REx to keep SOC sounds like a pain to me. They say 85% of all charging is done at home...

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

Re: BMW UK i3 REx without plugging in?

Thu Jan 07, 2016 5:51 am

The home charging problem COULD be circumvented in the future.
In the meantime there must be, or soon will be, a software tweak available to allow the battery pack to be fully charged using the petrol engine alone while stationary (don't mind keep topping it up with petrol or storing a spare can in the boot).
I realise this might sound like it defeats the purpose of using an electric car but
the unique driving experience and the futuristic design appeal more to me than charging with plug-in electricity (of which up to 70% is derived from burning huge amounts of fossil fuels here in the UK).
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

psquare
Posts: 483
Joined: Wed Oct 15, 2014 5:57 am
Location: i3 REx, 225xe Hybrid UK
Contact: Website

Re: BMW UK i3 REx without plugging in?

Thu Jan 07, 2016 7:28 am

Kundalini wrote:I realise this might sound like it defeats the purpose of using an electric car but the unique driving experience and the futuristic design appeal more to me than charging with plug-in electricity


Glad you've pointed this one out yourself. :D

Kundalini wrote:(of which up to 70% is derived from burning huge amounts of fossil fuels here in the UK).


Ok, three things:

You could of course switch to a renewable energy supplier, thereby personally supporting the increase of renewables in the UK mix. And 70% fossil a tad high, by the way. We're talking 45-55%, depending on demand, time of day and weather. Renewables are almost 20% at the moment, not even including PV. Gridwatch is good for relatively up-to-date figures.
http://gridwatch.templar.co.uk

You're also forgetting about effects on air pollution by having an emission-free car (when driven as a pure EV).

Anyway, enjoy your REx. :)

Return to “General / Main i3 Owners Forum”