New i3 book

[alohart]

On 17 June, David Bricknell, an i3 owner, published an iBook entitled Electric Vehicles and the BMW i3 (60Ah and 94Ah), a free download for those with an iOS or Mac OS X device. This iBook includes quite a bit of technical information that I know would interest some of you. A bibliography is included.

David is considering offering a PDF version for those of you without an iOS or Mac OS X device.

 

[Lithiumman]

This book is a great read for any EV owner not just for us i3 folk. I have learnt even more about my car through this book. David Bricknell goes into the technical details more than most. His scientific style, uses numerous diagrams and graphs, along with clear explanations about the many intricacies of electric cars making concepts that are new to most motoring enthusiasts, clearly understandable. While centered on the brilliant BMW i3, there are lots of references to, and explanations about, others EVs as well making this book important for anyone considering the purchase of an electric car. Particularly relevant, comprehensive and well explained are the sections on that core aspect of electric cars, the battery. Issues of capacity, chemistry, longevity, temperature, charging and management are now even better understood, yet I have been driving an i3 for 18 months. Thanks to David for his work on this text and making it freely available.

BMW i3 owner

 

[janner]

Great to hear that you like the book. It took quite a bit of time to put it together. Would appreciate it if you could post a review on the iTunes iBook site. So far I have over 200 sales/downloads.
David Bricknell

 

[Lithiumman]

Already put a review on iTunes, similar to what I wrote above. I am keen to promote EVs in any way possible hence, like you, I have also written an iBook and also made it a free download. "Supercharged Momentum : the century of the electric car". Hope the link works but if not just go to iTunes and search.

https://itunes.apple.com/au/book/supercharged-momentum/id814894431?mt=11

We are about 5 years behind the rest of the world down here in Australia thanks to a conservative government that tries to dampen any discourse on alternative energy, alternative transport or innovation. It's a very myopic attitude as we have more solar and wind resources than probably any other nation and this could bring us much wealth. Trouble is we also have huge coal resources and those with vested interests are big donors to the 'born to rule' mob and pulling many a political string. So my text may not be contemporary to the European EV scene. Not being as knowledgeable in the technical area and with the whole EV field so rapidly developing, I continue to correct and update it, but that is the beauty of this medium. I will have a few small corrections to make after reading your text, but it's all part of the creative process for me. Thank you.

John Murray

 

[busaman]

i would download it but i dont and wont own anything apple.... when it comes out in PDF format i will..

 

[janner]

John Murray. Thanks for your comments. I downloaded your book about a year ago when I bought my i3 and very much enjoyed reading it. Very professionally put together. I think our books are complementary.

 

[alohart]

i would download it but i dont and wont own anything apple.... when it comes out in PDF format i will..

Thanks for sharing.

 

[bwilson4web]

In this I would somewhat agree for different reasons:

i would download it but i dont and wont own anything apple.... when it comes out in PDF format i will..

I was able to download it but trying to read the iBook on an iPhone 6 brings new meaning to 'prescription font.' However, I was able to take screen-shots of selected pages and move them to a larger, readable screen. The format is getting in the way of the content and PDF or web page would be easier on my 'old man' eyes. Still, the few pages I 'screen captured' worked well.

Bob Wilson

ps. I've made a simple web page that supports downloading of my BMW i3-REx performance model:
http://hiwaay.net/~bzwilson/BMW/

Enjoy!

 

[bwilson4web]

Hi,

I'm beginning to approach the problem of how to measure the traction battery capacity. New, BMW reports it has a usable range of 18.7-18.8 kWh. I don't need a whole lot of precision so at lunch time I ran a quick hack:

• 87%->97% SOC change - upper 70F, in shade at Whole Foods
• 3.317 kWh - reported by the charger
  • ~3% SOC/kWh
    ~0.332 kWh/% SOC

The problem is 100% SOC would suggest 100*0.332 kWh ~=33.2 kWh ... obviously wrong unless someone slipped in the newly announced traction battery.

So I'm thinking I'll have to get on a constant speed loop after fully charging the battery and measuring with the Trip Meter what happens until the REx comes on. Any other suggestions?

Thanks,
Bob Wilson

 

[websterize]

Great job, janner. Very thorough work.

 

[jadnashuanh]

If you were to map the battery recharge rates, you'd find that it is by no means linear. Then, once the pack reaches close to 100%, it goes into a mode where it tries to do cell leveling, since not all cells are absolutely identical - some will reach full prior to others. Then, during discharge, the actual useable capacity of the pack will vary by temperature. SOme of that can be stabilized by the heating/cooling systems, but not all...some of it is based on the discharge rate, which heats things up.

 

[I33t]

Also, be aware that the battery capacity of your i3 will likely vary from the standard published numbers. You can see your actual cap via the hidden menu on the dash display.

 

[gt1]

Janner, I just finished the book. A lot of good information explained in the plain language. Thanks a lot for you work!

 

[gt1]

Hi,

I'm beginning to approach the problem of how to measure the traction battery capacity. New, BMW reports it has a usable range of 18.7-18.8 kWh. I don't need a whole lot of precision so at lunch time I ran a quick hack:

• 87%->97% SOC change - upper 70F, in shade at Whole Foods
• 3.317 kWh - reported by the charger
  • ~3% SOC/kWh
    ~0.332 kWh/% SOC

The problem is 100% SOC would suggest 100*0.332 kWh ~=33.2 kWh ... obviously wrong unless someone slipped in the newly announced traction battery.

So I'm thinking I'll have to get on a constant speed loop after fully charging the battery and measuring with the Trip Meter what happens until the REx comes on. Any other suggestions?

Thanks,
Bob Wilson

Try running the same test finishing with SOC under 80%. Should be more accurate.

 

[bwilson4web]

Also, be aware that the battery capacity of your i3 will likely vary from the standard published numbers. You can see your actual cap via the hidden menu on the dash display.

How do we access it?

Bob Wilson

 

[alohart]

How do we access it?

Follow these instructions.

 

[bwilson4web]

Also, be aware that the battery capacity of your i3 will likely vary from the standard published numbers. You can see your actual cap via the hidden menu on the dash display.

Hummm, I looked over the menu items (http://www.mybmwi3.com/forum/viewtopic.php?p=21323#p21323) and "13.08 Batt. Kapa. Max 19.8 kWh (maximum designed battery capacity)" reads more like how the car came from the factory versus some calculated battery capacity 'in service.' Did I miss something?

The more I think about it, running a constant speed test at 65 or 70 mph starting at 100% SOC to REx start, 6.5% may be the best and most accurate answer. I'll see if I can find a time-lapsed photo app for the iPhone and use it to document the experiment. This can also help us understand the non-linear, %SOC.

Bob Wilson

 

[janner]

This may be helpful to you in establishing the battery capacity - there are four BEVs and four BEVxs.
https://avt.inl.gov/sites/default/files/pdf/fsev/fact2014bmwi3ev.pdf

It's important to remember that battery capacity isn't absolute. It varies with temperature but more importantly it varies with discharge rate; the harder you drive the car the more difficult it is to get the energy out.
I've covered this in my book.

 

[jadnashuanh]

The pre-2017 i3's have a 22Kw battery...what you see is the amount they will allow you to use. That number does change based on the temp, and the age of the batteries.

 

[janner]

The nominal gross capacity of the battery is
96 cells x 60Ah x 3.75v = 21.6kWhrs
Max cell voltage is 4.1v which would equate to 23.62kWhrs but it would be instantaneous as voltage would drop as soon as you start to use it.
There is a reserved amount both top and bottom and once you subtract that you're left with the net usable amount.
The net usable amount depends on cell temperature and rate of discharge. If you drive the car hard then the net usable amount of battery is less than if you drive the car gently.
BMW quotes 18.8kWhrs but not the c-rate. It's probably one-third C and at a one C rate the net usable is nearer 18kWhrs.