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Does preconditioning reduce range?

Discussion in 'General EV Discussion' started by SteveD99, Jan 10, 2017.

  1. SteveD99

    SteveD99 Active Member

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    Preconditioning a car obviously uses power. I always thought that if the car was plugged in while preconditioning, the power was being taken from the mains and therefore had no impact on the battery and therefore range. Recent experience with my Zoe (R240) suggests differently.

    To benefit from Economy 7 I use the scheduled timer to start charging at 12:30am. Charging might finish between 4am and 5am at 100%. The preconditioning starts at 6:45am ready for a 7am departure. So I get in the car expecting 100% charge - only to find it is down to 97% or 98% (lowest I think was 94%). A few times the car has started charging again a couple of minutes before I need to unplug.

    So, this suggests that the preconditioning has been draining the battery. Have any other EV owners had the same experience? Is it something unique to the Zoe or do other models do the same thing?
     
  2. Prg350

    Prg350 Active Member

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    With the Leaf it will remain at 100% so only draws from the mains, not the battery. I don't have any charge timers set tho. The guessometer seems to drop a few miles with lots of preheating but then I usually ignore that anyway
     
  3. oxonEV

    oxonEV New Member

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    I have a timer set every morning to pre heat - no scraping yippee - and my Leaf is usually a 98% if it has had to do a lot of preheating despite being plugged in to charger. Warm morning air temperature = 100% battery. Perhaps the draw of full heating is more than the cable supplies so it drains the battery?
     
  4. davebodger

    davebodger Active Member Speak EV Supporter

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    Yes, my car does this. As far as I can see, the electric heater ramps up to at least 4.5KW over a 10 minute period.
    The charger in my car can only grab 3.6KW from the cable, or 2.4KW if it is on the granny lead, so at the end there is a deficit.
    If I leave it on charge for a further 10 minutes it seems to replace most of the charge but I would have to leave it for an hour to top it up properly to 100% because the charge rate is so slow at the top end.
    Kind of defeats the preconditioning if you don't drive it straight away. :)
     
    fr0d0 likes this.
  5. Mr_G

    Mr_G Well-Known Member

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    Even with a 6.6 kW charger on a 24 kWh car the battery still drops to 98% when it is a defrost the glass job for the preheat. I don't mind 2% loss to be able to jump into a warm and glass clear car. Normally the worst I get in winter averages out at 4.1 miles /kWh but first few percent from 100% always disappear very quickly in normal driving. If I drive uphill away from home 1% goes in about 0.1 mile and the GOM loses 10 miles of range down to 80 miles in the blink of an eye. :eek:
     
  6. Zoe Al

    Zoe Al Zoe Q210 Dynamique Intens

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    This is not the preconditioning draining the battery, it is the fact that a cold battery can't hold as much charge as a warmer one. So a level of charge held that is 100% when the temperature is around 0c overnight would correspond to 96 or 97% charged when the battery warms up as 7am approaches at the temp for example is 3c warmer. Mine does the same even if preconditioning is not active.

    Zoe's will draw 32a & have heat pumps so the heater doesn't appear to overwhelm the charging cable. Also I think timer preconditioning may be weaker than the 5 min blast from a key fob press, but as it will last up to 30 mins manages to make the car toasty & warm.

    Preconditioning the car will warm it (& the battery) up highlighting rather than causing the issue.

    Teslas have battery warming circuits to overcome this.
     
    Last edited: Jan 10, 2017
    Hairy Leafer and Bibsy like this.
  7. donald

    donald Well-Known Member

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    If it is anything like the Fluence, IIRC I had to set the timer 30 minutes before I actually wanted to leave else it'd not have completed its heat-up cycle and recharge, which took around an hour in cold conditions to get properly warmed up and ready set. So although ostensibly it was a 30 min warm-up (so would crank up at say 7AM for a 7:30 setting/departure), it took more than that to do the task properly. (e.g. - want to leave at 7:30, then set the leave time as being 7AM, so it'd crank up at 6:30 and it would 'over-run' for the next 30 mins past 7AM)

    As it happens, I am finding this with the Ampera too. The two preheats at the 3kW rating from the plug aren't quite enough to heat the cabin through in the 20 minutes the preconditions have to do that. Instead I have to turn the car on and let it reach an equilibrium that way, all powered up, and it generally takes 45 min to an hour to do that and settle back to a fully charged state.
     
  8. Zoe Al

    Zoe Al Zoe Q210 Dynamique Intens

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    With the Zoe if you set it for 7:30 if it starts about 7:00 or 7:10. If we have left late it won't over-run by 30 mins, just 5 or 10 mins.
     
  9. donald

    donald Well-Known Member

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    I thought it might have been like the Fluence, which I think kept going for 40 mins.

    All the same, maybe it is worth allowing it to complete the cycle, then it may top up at the end.

    Do you really need the full battery? In the Ampera we need every Wh, as it translates into using fuel for me every day at the moment, a litre or so.
     
  10. Bibsy

    Bibsy Active Member

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    I set my pre-conditioning for 7:00 each weekday. I'm up and about from 5:45, and you can hear the Zoe start the fans please at any time from about 6. Depends on the temperature, but definitely had pre-soak kick in an hour early.
     
  11. Zoe Al

    Zoe Al Zoe Q210 Dynamique Intens

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    You are a bit further north than me as a southern softie!! That makes sense that it is only trickle heating rather the full blast then.
     
  12. donald

    donald Well-Known Member

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    What I found with the Fluence (I am referring to it, on the logical assumption that the same engineers would have likely worked on both systems, ergo the same 'operating logic' for the Zoe) was that it would start around an hour early, as you say, but then might turn off, or it might keep on heating up.

    The impression I got was that it does a 'test heat' for a few minutes an hour beforehand, and sees how quickly the car is warming up. It then decides if it is a 'warm' day or 'cold' day, and works out what the starting time should be to get to the set temperature at the set time, and not start up earlier than needed. If it struggles to get the car warming up during the test cycle, it'll just stay running. That's my theory/reverse-engineering.
     
  13. Zoe Al

    Zoe Al Zoe Q210 Dynamique Intens

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    Am I correct that the Fluence has a standard rather than heat pump heater & only 3 kw charging?

    If so for the same time on a home charger, a Zoe can take 6 times the heat. It is also a bigger car so will need more heating. The sales brochure also said it purposely had smaller windows to make it more thermally efficient rather than using an existing bodyshell.

    My assumption from all that is that with a car more specifically designed they would be mad to just use the same software algorithms.
     
  14. donald

    donald Well-Known Member

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    I can't see why. If the logic of starting up heating early as a means to determine when to actually start the heating 'proper', so to speak, was what Renault did initially, I can't see why the power level would change that philosophy.

    Certainly towards the end of the heating phase, you want to be drawing the barest minimum of power, so makes no difference if you have 2kW or 2MW.
     
  15. Zoe Al

    Zoe Al Zoe Q210 Dynamique Intens

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    My only thought is heating very early is wasteful as more heat will be lost.
     
  16. Zoe Al

    Zoe Al Zoe Q210 Dynamique Intens

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    Must be cheaper in electricity to check outside / cabin temp rather than throw heat at it to check when full blown heating needs to start.
     
  17. donald

    donald Well-Known Member

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    It's not hugely wasteful. There is a certain quantity of thermal energy you need to put in to get the cabin to temperature. Whether you do that an hour before you leave, or only after you leave, it is the same quantity of energy.

    The 'extra' is 'merely' the thermal power loss during the transition from cold to warmed-up. When warmed up a typical car is somewhere in the 1.5kW loss range, so if it took say 45 mins to warm up, then steady for 15 mins, that'd be less than 1kWh extra for the whole hour's worth of heating, over and above being freezing cold at the start for 5 mins and not being able to see through your misted/frozen windows. At E7 rates (if you are leaving during that time) I'd say 1 kWh was money well spent.
     
  18. BSven

    BSven Well-Known Member Speak EV Supporter

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    Location:
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    It seems like the Leaf has some extra consideration for roof insulation that perhaps helps with reducing heating losses:

    Thermal Insulation Roof

    While it seems sensible that EV's try reduce heating losses, I don't know if this is any different from normal cars.
     
  19. Zoe Al

    Zoe Al Zoe Q210 Dynamique Intens

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    In normal cars heating is a by product of combustion so effectively free. In an EV heating has to be paid for so efficiencies are more important.
     
  20. donald

    donald Well-Known Member

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    Virtually insignificant.

    If you drive somewhere (with the heating on!! ;) ) when there has been a hard frost, when you get out and see there is still frost on the car roof, do you notice all the ice has gone from the windows? That's because, .. this is my guess, 85% of the thermal path is via the windows.

    The best improvement would be double glazing. Merc S models used to have it. Can't see the issue with making it for EVs, it would not be a huge cost and would easily save the cost/CO2 in one winter.
     
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