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Discussion Starter #1
I did a search on here and a few other websites, which confirms my fear that unfortunately you can't set the i3 to charge in off-peak (Octopus Go) hours without setting a departure time so it can also precondition the battery.

My Podpoint charger also doesn't offer any sort of control over timing.

This seems a pretty ridiculous situation to me and I'd rather not spend more money on special ohme cables or a replacement wall charger.

Is there an easy way I can abort the preconditioning cycle after its charged overnight?

Even better, a way to automate this using smarphone or computer?
 

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Not perfect but you could set the departure time daily to just one day a week.
Would it not then wait until the night before the departure day before charging?
It might help, but I'm really hoping to be able to charge/top-off daily.
 

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Set the departure time for one day a week at a late morning time and set the charge band (I use 12.35 to 04.30 am for Octopus Go). That works whenever you plug the car in. I don’t think it will precondition for that time unless you set pre-condition. Not sure but I always unplug next morning anyway. It’s not intuitive. If you get stuck I will check my set-up and let you know which boxes to tick.
 

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Discussion Starter #6
Not perfect but you could set the departure time daily to just one day a week.
Well it seems I owe you an apology for dismissing this suggestion. I'm sorry, still getting used to some of the slightly odd design logic.

Yesterday I set the departure time for 11am on Wednesdays, unticked precondition (cabin temp) and plugged in the i3.

It charged up overnight just fine.

I will see what happens on Wednesday - I suspect it will heat up the battery from 10:30-11am ready for departure. This is the bit I want to try and cancel/abort.
 

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That's why you set it for a later time, so that you can unplug it in the morning...
 

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Someone might know the relative temperatures of the battery after charging and preconditioning.

maybe then you could set the departure time in line with charging time in such a way that the battery is already close to desired temp and the preconditioning doesn’t activate or is minimal?
 

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Preconditioning takes the battery up to 10 deg. C. (I have read that it takes it higher but not according to the experts) because regen. is inhibited below that. I have only used preconditioning in very cold weather where range is important because the car heats up very quickly once underway. I guess you can pre-cool (?) but leaving the windows open for a while works pretty well.
 

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A useful article albeit from 2015. It doesn’t give any indication of what temperature the batteries would get to when charging altho obv this would vary depending on time elapsed, charge rate and ambient temps.
 

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The batteries are heated to 10 deg. C. That’s the only preconditioning. They may, of course, get warmer during the charging process but not by deliberate intent.
 

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Ok so if 'normal' battery operating temp is 25C to 40C and preconditioning heating is only on upto 10C then setting a departure time a few hours after charging has finished should mean that (in the uk at least) the battery is still warm enough from charging to not activate the battery heater.

What would complete the picture is the temp the battery gets up to after a few hours charge at 7kw and whether battery cooling might kick in?
 

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The optimum temperature for efficient battery operation is between 25 and 40 deg. C. I think that the charge rate would be reduced if the temperature is too high but the cooling would kick in above 40 deg. C. It can take several hours to stabilise the battery temperature. I don’t believe that level of technical information you are asking for is available and, in any case, would be entirely ambient temperature dependent. Bear in mind also that the charging current varies over the range depending on SOC.
 

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Pre conditioning works as follows


“For the i3, preconditioning of the battery takes approximately 3 hours to raise the battery cell temperature to 10oC (where regenerated energy will be accepted by the battery) and takes around 0.5 to 1kWhrs of energy; driving the car will cause battery chemical reactions to take place ensuring that the cell temperature increases further towards the optimum.”

— Electric Vehicles and the BMW i3 by David Bricknell

“The precondition process when setting a ‘departure time’ requires 3-hours to implement and the i3 needs to be plugged in to at least a 220V/ 10A supply. The final part of the pre-con process is cabin heating and this can take a further 0.5kWhr and maybe up to 3kWhrs of energy with peaks of 5kW power in very cold conditions but for shorter periods of time. The car takes the power directly from the charging socket and will top it up with battery power should cabin heating demand higher power than is available. This means that you may have less than 100% battery SOC on departure unless your charger can provide at least 7kW.”

— Electric Vehicles and the BMW i3 by David Bricknell


Best bit of money I have ever spent on an ebook explains everything about the i3 - loads of graphs etc.

NB the battery is only heated to 10C so that the regen works, once you are driving the battery then continues to warm. The heating system does not heat the battery to 20/25C which is optimum just enough so the Regneration works. Also it is not a steady heat but pulses which start and stop to allow the heat to dissipate in the battery. Also if you charge at 00:30 for 4 hours at 7kw on Octopus Go this will have probably got the battery to 10C anyway so then only the cabin preheat will kick in 20 minutes before departure.
Anyway you can read more in this excellent book (y)
Electric Vehicles and the BMW i3
 

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A useful book, expensive and not indexed but there’s nothing else out there. It has been updated for the 120 Ahr. and I was quoting from it.
 

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A useful book, expensive and not indexed but there’s nothing else out there. It has been updated for the 120 Ahr. and I was quoting from it.
Only £4.90 for the kindle app worth every penny. Finally understood what was on the drive after reading this. Spent a couple of afternoons reading it cover to cover and yes updated for 120 Amp Hour so well up to date.
 

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Took some numbers down today - ambient 14c, battery still at 9c as it was a cold night.

30 mins on rapid 50kwh batt temp went up to 23c.

wouldnt normally charge to full but in the interest of science 45mins on the rapid and batt temp read 24c.

Drove around town stop start stuff for an hour after that, sun came out and ambient rose to 17c, battery temp barely moved from 24C

...and 90 mins after parking up, ambient temp still at 17C the battery has only dropped 1 degree to 23c.

...and 4 hrs after parking up, ambient has dropped to 15C and the battery has only come down to 21C

...and next morning 9.30 am,18 hours after parking up, a mild night but temps did dip as low as 7C and the batt temp is still at 14C! So it looks like it takes an age for the battery pack to dissipate heat.
 

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Took some numbers down today - ambient 14c battery still at 9c as it was a cold night.

30 mins on rapid 50kwh batt temp went up to 23c.

wouldnt normally charge to full but in the interest of science 45mins on the rapid and batt temp read 24c.
Good to know, now do 4 hrs on a 7kw would be interesting what it gets to on that at night :)
 
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