REx auto kick-in point

[RJSATLBA]

Just trying to draw some stuff together from various threads, particularly the Range for Speed thread and the What Car thread.

I'd seen the item in the UK glossy price list on the standard equipment page where it states that for the REx model the REx auto starts at 18-20% soc but had also seen the US unhappiness that it doesn't kick in until about 4%, without the facility that exists on EU cars to invoke the REx manually to maintain charge once below 75%. From this I'd assumed that taking a range of say 80 miles a US REx would come on at 3-4 miles, with no option to maintain a higher soc whereas in Europe the REx would come in at about 15 miles but could be invoked manually from about 60 miles remaining.

I've now seen the comments about trying out the auto start in the UK, all of which refer to it coming in at around 2-4 miles, which sounds more like the US set-up than the EU one.

Is my confusion down to ambiguity where the official reference to it coming in at 18-20% refers to the absolute battery capacity of 22.2kwh, not to the usable capacity, so 18% would be at 4kwh, of which of which 3.4 is unusable (22.2-18.8), leaving only 0.6kwh usable. This seems more in line with contributors referring to it not kicking in until the range is down to 2-4 miles?

Have just seen surfingslovak's post in the Range for Spped thread in which he or she says that the absolute capacity of the battery is 21.6kwh, which kills my back of the envelope arithmetic, can anyone clear this up for me?

 

[TomMoloughney]

Just trying to draw some stuff together from various threads, particularly the Range for Speed thread and the What Car thread.

I'd seen the item in the UK glossy price list on the standard equipment page where it states that for the REx model the REx auto starts at 18-20% soc but had also seen the US unhappiness that it doesn't kick in until about 4%, without the facility that exists on EU cars to invoke the REx manually to maintain charge once below 75%. From this I'd assumed that taking a range of say 80 miles a US REx would come on at 3-4 miles, with no option to maintain a higher soc whereas in Europe the REx would come in at about 15 miles but could be invoked manually from about 60 miles remaining.

I've now seen the comments about trying out the auto start in the UK, all of which refer to it coming in at around 2-4 miles, which sounds more like the US set-up than the EU one.

Is my confusion down to ambiguity where the official reference to it coming in at 18-20% refers to the absolute battery capacity of 22.2kwh, not to the usable capacity, so 18% would be at 4kwh, of which of which 3.4 is unusable (22.2-18.8), leaving only 0.6kwh usable. This seems more in line with contributors referring to it not kicking in until the range is down to 2-4 miles?

Have just seen surfingslovak's post in the Range for Spped thread in which he or she says that the absolute capacity of the battery is 21.6kwh, which kills my back of the envelope arithmetic, can anyone clear this up for me?

The total pack size of the i3 is 21.6kWh, even though you'll typical read it has a 22kWh pack. Of that, only 18.8kWh's is usable, and all references to the state of charge will be a percentage of the usable portion of the battery (18.8kWh) so if you turn the Rex on at 10% state of charge, at that point you only have about 1.8kWh's of energy at your disposal. It's not an exact science though (determining the battery pack's current state of charge at that moment) so expect some slight variation from time to time.

 

[SanSerif]

The UK spec (well, mine at least) auto-triggers at around 5% but can be manually triggered below 75%.

I suppose this is better than having the auto-trigger hardwired at 18% as once mooted; you have flexibiity but, if you forget to do anything, the computer will save your bacon at the last minute. It might be nice to be able to set the auto-trigger point - but in pursuit of electric miles I'd probably set it low anyway.

 

[RJSATLBA]

Tom and SanSerif, it sounds like the explanation is much simpler, BMW have changed the kick in point for European cars from around 18-20% to 5% since the brochure and price list were published.

 

[surfingslovak]

Is my confusion down to ambiguity where the official reference to it coming in at 18-20% refers to the absolute battery capacity of 22.2kwh, not to the usable capacity, so 18% would be at 4kwh, of which of which 3.4 is unusable (22.2-18.8), leaving only 0.6kwh usable. This seems more in line with contributors referring to it not kicking in until the range is down to 2-4 miles?

Have just seen surfingslovak's post in the Range for Spped thread in which he or she says that the absolute capacity of the battery is 21.6kwh, which kills my back of the envelope arithmetic, can anyone clear this up for me?

Roger, it's easier and better to do this calculation with the usable battery capacity. This is the energy, which should be available from the battery to drive the wheels. If you assume 5% SOC kick-in point for the REx, this leaves about 0.9 to 1 kWh of usable energy in the battery. Once the REx gas tank is exhausted, and assuming that the battery kept its charge, you should have another 4 to 5 miles left at normal driving speeds. More if you slow down considerably. I hope this helps. As Tom said, the SOC is an inexact science, and batteries are chemical beasts, which are not as predictable as the digital gadgets most of us are accustomed to. Well-manufactured high-quality batteries will have highly predictable performance and lifecycle, but the devil is in the details, literally.

 

[Tommo]

Hi

i picked up my Rex on Monday and decided to go all out and drive it on a 180 mile round trip today using a combination of battery, rex and a public charging point

I had been informed by the iGenius that the Rex kicked in at a pre-determined point but when the charge got to about 20% I set the Rex maintain that SOC as I was concerned that I would need some battery later on....not sure what point the auto-kickin point is.

The Rex did a great job, it did not make too much noise and kept the SOC at the 20% mark....

I had a major problem with Ecotricity charging point at Clacket Lane services - it just had the message "waiting for charging request from vehicle" on the screen. When I called the Ecotricity help desk they said that owing to a software issue many of their charging points are not compatible with the i3 but they will be upgraded over the coming year!!! She said some work and some don't.....which is not good for planning a trip.

I filled up with petrol and continued on the journey....I used a full charge and one and a half tanks of fuel...not the most economical trip but it proved to me that the i3 is a very capable car.

The range forecast is very accurate...I did get the battery charge down to 3miles and 5 miles on the Rex which was quite worrying and the Rex sounded like a washing machine on full spin!

 

[SanSerif]

Interesting that Ecotricity's points don't work. Can't complain too much seeing as they're providing the service free of charge. I assume that you were using one of the "fast" points where you need to bring a cable rather than a "rapid" (which has its own cable). Did you get it to work at all? I've read that Ecotricity are starting to roll out CCS rapids so hopefully we won't need to hang around for hours at motorway services soon.

I've yet to do a big run in mine. I clocked up 102 miles travelling to Farnborough and that's my max. I wasn't diligent enough to record how much of that was on battery and how much on REx. If I do the trip again, I'd try and squeeze the most possible out of the battery. I did manage 70 miles on battery the other week - with 20 remaining on the predict-ometer.

 

[Tommo]

Hi

I got the public charging cable from the BMW dealer at a cost of £165.....

indeed you cannot complain if it is free....the Ecotricity unit had a tethered cable so I just plugged that in but the unit was having none of it sadly so i had to give up

I noticed that Whiteley Shopping Centre have Pod-Point charging units which are also free, I will apply for one of their cards too (£12.50) and the Charge Now card (£20)

What EVSE have you had installed at home? I am getting the pod-point universal as it is so much smaller than the BMW one.

The car gets LOTS of attention!!

 

[SanSerif]

I think I may have identified your charging problem.

Clacket Lane only has the "rapid" chargers - not the slow "fast" chargers (!) The current generation of Ecotricity rapids can't charge i3 (or VWs or any other EU standard CCS-fitted car(!)).

Ecotricity are starting (imminently, allegedly) to upgrade rapids to triple-headed jobs (Nissan-standard, Renault-standard and CCS-standard) - but, until they get round to it, the only Ecotricity chargers you can use are the slow "fast" chargers (marked in blue as "AC medium" on their maps).

Anyway, I'm glad you tried it. I'd wondered what would happen if you tried to plug into (presumably) the AC side. I'd hoped that it would just sup at a slower rate.

 

[SanSerif]

Re: home charger - none fitted as yet. When I get round to re-homing the bicycles in the garage, I'll order one. As you note, the BMW one is monstrously big an unnecessarily expensive so I'll get something smaller.

Just plugging into a 3 pin socket seems fine at the moment. There's not many time when I clock up multiple long journeys in a day and need speedy recharging. Waking up to a full tank is all I need - so it's fine if it takes all night.

 

[BrianStanier]

Anyway, I'm glad you tried it. I'd wondered what would happen if you tried to plug into (presumably) the AC side. I'd hoped that it would just sup at a slower rate.

From the message it would seem that it was plugged into the AC side. but there'a handshake problem. I suspect that will be true for some of the 7kW fast chargers too - some Leafs don't talk properly to them either.

 

[Houdini]

So the way I read it you can manually trigger the Rex to maintain the level of charge you want. But it will automatically come on at 5%. If you run it out of fuel does it switch back to battery then and allow you to run the i3 right down, perhaps even out?