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Discussion Starter #1
Not trying to troll here but I’ve been trying to preheat my Leaf to see if it makes any difference to the range and to be honest, I just can’t seem to get it to make a difference. No matter if I just warm the car for 5 mins or 1 hour, it doesn’t seem to make any significant difference to my journeys / commute and thinking about it, I just can’t see why it would!
Even if you heated the whole car (including the batteries) to a toasty 20 degrees, the moment you started driving in cooler weather, the wind chill alone would reduce the batteries to the ambient temperature in a few minutes! There’s no way that using the heater alone would keep the batteries at a warmer temperature as, as far as I can see (and I could be wrong!) as no warm air from the heater is directly diverted to the batteries anyway.
So, how is it supposed to work? Why would increasing the battery temperature for a few minutes give you significant increases in range for the duration of your journey?
Can someone please explain it to us noobs?
 

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Discussion Starter #3
Yup, I get that but apart from warming up the interior, aren’t people saying that it affects range too?
 

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For the Leaf, pre-heating doesn't heat the batteries. All it does is heat the cabin and whatever energy it uses to do that is energy you have saved from your batteries and so can use for driving rather than heating thus "extending" range. Its not really extending range just not wasting energy on cabin heating thus reducing range.

The amount of saved range you will get will be relatively small.
The main benefit is a warm car as soon as you sit in, rather than waiting 5mins for it to heat up.
 

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Yup, I get that but apart from warming up the interior, aren’t people saying that it affects range too?
Say you get 3 miles per kWh. If you use 1 kWh pre-heating the car while it's plugged in rather than taking it from the battery, then that's 3 miles of extra range you have available when you start driving.
 

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The battery is really warmed by charging. If I could be bothered before a longer journey I could:
1. Rapid charge the car at the local charger to 85% (adds 1 to 2 bars of battery temp).
2. Drive home and plug into slow charger whilst loading up. (To 100%).
3. Drive off with a warm battery and more range.

In reality I just accept (on very long journeys) that my range to my first rapid is limited in colder weather. After the first rapid the battery performs better.

Some countries have a "cold pack" battery heater. For them battery preheat is a real and necessary thing.
 

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Discussion Starter #7
Yes, I totally get that! You’d be crazy to preheat on battery but I swear a few people have mentioned that heating extends range! I must have been imagining it (or looking on another ev forum lol)
I’ve been trying for days to get it to make a difference. <facepalm>
 

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I think the point is you're supposed to do it while still plugged in, meaning you don't use any precious kWh just warming up the car once you start driving. Once you unplug it makes no difference.
Interesting. Charged the Leaf overnight as usual - it had plenty of time to get to 100% (even with 2 to 3 hours cell balancing) as it was well charged anyway.

Kicked off pre-heat about 20 minutes prior to leaving (still connected to the 16 amp charger). Jumped into the nice toasty car ....

.... dash tells me there is 98% charge. Where did my 2% go?
 

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Interesting. Charged the Leaf overnight as usual - it had plenty of time to get to 100% (even with 2 to 3 hours cell balancing) as it was well charged anyway.

Kicked off pre-heat about 20 minutes prior to leaving (still connected to the 16 amp charger). Jumped into the nice toasty car ....

.... dash tells me there is 98% charge. Where did my 2% go?
From what I can tell what it does is it goes in a cycle as follows...

1) Turn on heater for pre-heat, powered by HV battery
2) % drops so the charger replenishes the battery
3) Continue heating
4) Go to step 2

So, if it happens to finish the pre-heat before step 2 finishes it can leave you down a percent or two.


Another way it can also happen, particularly if you are using a granny EVSE or a 16A charge point, is that if the main charging process is still in progress when the pre-heat comes on the EVSE won't be able to provide enough power to charge the car and pre-heat so it can leave the car a few percent short (i.e. it never gets to 100% in the first place). Thats not the case for you based on your description above.

The trick, if you plan to use pre-heat, is to ensure that the main charging process is finished well before pre-heat is likely to start.... give it a good 45mins+ so that charging and pre-heating don't overlap.

Its less likely to happen if you have a 32A charge point and a 6.6kW charger in the car as it will have enough power to drive the heater and charge at the same time.
 

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It can lose a few percent because the heater is rated at 5Kw so if are charging by any means less than the 6.6Kw charger it can use a bit of battery it would top this up again if it was left charging.
 

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@Mr Roboto pre-heating just does the passenger cabin like you said and its probably 90% for comfort thing. That said, i find getting the car up to temperature takes a lot more energy than maintaining the temperature. Check out the energy info screen for proof.

+Wind chill is not as bad as you think. The car and its batteries are a huge thermal mass and it takes hours for them to cool down.
 

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I think the point is you're supposed to do it while still plugged in, meaning you don't use any precious kWh just warming up the car once you start driving. Once you unplug it makes no difference.
In practice it doesn't seem to work that way, I've got one of those electricity usage monitors and I watched it the first time I tried pre-heat in the morning. Batteries were initially full. No current was drawn from the charger.

Now maybe if was on long enough to lower the battery enough it might trigger a new charging cycle, but its unlikely it would be on long enough. There's a limit, I think 15 minutes. Of course I've got the charging timer on these days so that wouldn't happen anyway.

Only advantage of pre-heat is a warm (or cool) car to get into. To maximise range - dress warmly.
 

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In practice it doesn't seem to work that way, I've got one of those electricity usage monitors and I watched it the first time I tried pre-heat in the morning. Batteries were initially full. No current was drawn from the charger.

Now maybe if was on long enough to lower the battery enough it might trigger a new charging cycle, but its unlikely it would be on long enough. There's a limit, I think 15 minutes. Of course I've got the charging timer on these days so that wouldn't happen anyway.

Only advantage of pre-heat is a warm (or cool) car to get into. To maximise range - dress warmly.
UPDATED based on correction from posters below...

There are three versions of pre-heat....

1) The manual 15min pre-heat that you kickoff from the app when the car is not plugged in
2) The manual upto 2hr pre-heat that you kickoff from the app when the car is plugged in
3) The auto pre-heat from the timer you set in the car.

For 1) its limited to 15mins and obviously uses energy from the battery.
For 2) it shouldn't use much, if any, battery power as it will recharge it from the charge point as the battery runs down.
For 3) it will run for much longer than 15mins, depending on outside temperature, and will topup the battery from the charge point. This timer only works when plugged in.
 

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There are two versions of pre-heat....

1) The 15min pre-heat that you kickoff from the app.
2) The pre-heat from the timer you set in the car.

For 1) its limited to 15mins and uses energy from the battery regardless of whether it is plugged in or not and you will lose range that way.

For 2) it will run for much longer than 15mins, depending on outside temperature, and will topup the battery from the charge point. This timer only works when plugged in.
For 1) are you sure it stops at 15 mins, even if plugged in?
If plugged in I thought it would go for an indefinite period, only stopped when you unplug.
 

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Not trying to troll here but I’ve been trying to preheat my Leaf to see if it makes any difference to the range and to be honest, I just can’t seem to get it to make a difference. No matter if I just warm the car for 5 mins or 1 hour, it doesn’t seem to make any significant difference to my journeys / commute and thinking about it, I just can’t see why it would!
Even if you heated the whole car (including the batteries) to a toasty 20 degrees, the moment you started driving in cooler weather, the wind chill alone would reduce the batteries to the ambient temperature in a few minutes! There’s no way that using the heater alone would keep the batteries at a warmer temperature as, as far as I can see (and I could be wrong!) as no warm air from the heater is directly diverted to the batteries anyway.
So, how is it supposed to work? Why would increasing the battery temperature for a few minutes give you significant increases in range for the duration of your journey?
Can someone please explain it to us noobs?
You need around 1.5 to 2 kWh flat to heat up the cabin to operating temperature. Of course, if you are happy to drive out in a cold car and wait for it to heat up very slowly, then sure it won't make a difference.

There is simply no way that 250kg of solid mostly-metal will revert to ambient temperature in minutes. Your pack will still be warm the next morning from a drive in the previous evening.
 

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The preheat activated from the app will run for 2 hours when plugged in or 15 minutes if unplugged.
Thats why I left the 1%! ;)

Must test that this evening!

It escapes me why someone would want a 2hr pre-heat.... thats a lot of wasted energy!
 
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