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Hi People

Having owned my 24kw 17 Reg leaf for over 1 year I have noticed that in cold times ( Like now ) I get about 6 miles less on the GOM

Are cold Batt's less efficient than say 20 degree temp Batt's ?

Hope you all made the best of Christmas and the new year ( With restrictions )
 

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In a word, Yes. All BEVs do, although most modern designs offer the facility to heat the battery. In some colder climates the LEAF came with resistive heater elements for the battery but they work best below -5C as above that they use more energy than the extra that a warmer battery releases.
 

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Short answer:

Yes lithium batteries don’t really like the cold, they don’t hold as much charge when the charging is done at lower temperatures, you can’t charge them as quickly and they don’t operate as efficiently.

They like to be in a “Goldilocks zone” of between about 15’c - 30’c this varies a little depending on the battery chemistry and who you ask! 😃
 

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Hi People

Having owned my 24kw 17 Reg leaf for over 1 year I have noticed that in cold times ( Like now ) I get about 6 miles less on the GOM

Are cold Batt's less efficient than say 20 degree temp Batt's ?

Hope you all made the best of Christmas and the new year ( With restrictions )
There's many reasons to get less range in an EV in winter and some that apply to all cars including ICE...

All cars have increased rolling resistance if the road is wet - wet roads have a surprisingly large effect, sometimes as much or more than dry cold, and wet slushy snow is even worse. Cold air is thicker causing more drag at higher speeds.

But some range loss factors are EV specific - power consumption from heating and cold battery as you mention.

A cold battery is indeed a bit less efficient because the internal resistance goes up especially if it gets down near or below freezing. This higher internal resistance increases I^2R or ohmic losses in the battery.

These losses are highest at high power levels, so the efficiency loss of a cold battery is worst if you are are accelerating or braking hard while if you drive more conservatively it minimises the effects of the higher resistance.

On the other hand, the increased losses of a cold battery cause more heat generation in the battery and help to warm it up, so with enough driving the battery will eventually warm up to a more agreeable temperature.

But there is a second factor as well which is probably more important - the usable capacity of the battery reduces at low temperatures.

When a battery is under load the voltage drops, and to protect the cells they can't be allowed to go below a certain voltage at any time. (Approx 3 volts per cell or slightly higher depending on the car) As the battery discharges the voltage also drops so the combination of SoC and load sets a lower limit on how low the battery can be usefully discharged without getting to a dangerously low voltage.

When the battery is much colder the internal resistance goes up increasing voltage drop for the same load and as a result it can't be discharged to as low a SoC under load without dipping below the minimum allowed voltage.

In essence some of the bottom end capacity of the battery has to be "walled off" to protect the cells and becomes temporarily unavailable. The BMS takes account of the cell temperatures and scales the reported SoC on the dashboard to "hide" this missing capacity.

So if you had a battery that had say 25kWh usable capacity at 20C you might find that it only had 22kWh usable capacity at -5C while still staying above the minimum allowed cell voltages. As soon as the battery warms up the "missing" capacity is available again.

As long as you drive relatively conservatively I suspect the reduction of usable capacity with cold is more important than the reduced efficiency caused by higher internal resistance.

And both these battery effects are smaller than the increase in power consumption of simply trying to keep the car warm with the heater. If it's very cold dropping the cabin temperature a couple of degrees and turning the seat heaters on can make quite a difference to range especially on a Leaf where a low heat output can be managed by the heat pump while a high heat output calls upon the resistance heater as well.

As for what you can do about these various winter range loss mechanisms - plugged in preheating can save as much as about 2.5kWh (equal to about 8 miles range in winter) so is well worth doing, also if you use the charge time to delay charging until the early hours of the morning the charging of the battery just a few hours before you use the car will help warm the battery a few degrees.
 

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There's many reasons to get less range in an EV in winter and some that apply to all cars including ICE...

All cars have increased rolling resistance if the road is wet - wet roads have a surprisingly large effect, sometimes as much or more than dry cold, and wet slushy snow is even worse. Cold air is thicker causing more drag at higher speeds.

But some range loss factors are EV specific - power consumption from heating and cold battery as you mention.

A cold battery is indeed a bit less efficient because the internal resistance goes up especially if it gets down near or below freezing. This higher internal resistance increases I^2R or ohmic losses in the battery.

These losses are highest at high power levels, so the efficiency loss of a cold battery is worst if you are are accelerating or braking hard while if you drive more conservatively it minimises the effects of the higher resistance.

On the other hand, the increased losses of a cold battery cause more heat generation in the battery and help to warm it up, so with enough driving the battery will eventually warm up to a more agreeable temperature.

But there is a second factor as well which is probably more important - the usable capacity of the battery reduces at low temperatures.

When a battery is under load the voltage drops, and to protect the cells they can't be allowed to go below a certain voltage at any time. (Approx 3 volts per cell or slightly higher depending on the car) As the battery discharges the voltage also drops so the combination of SoC and load sets a lower limit on how low the battery can be usefully discharged without getting to a dangerously low voltage.

When the battery is much colder the internal resistance goes up increasing voltage drop for the same load and as a result it can't be discharged to as low a SoC under load without dipping below the minimum allowed voltage.

In essence some of the bottom end capacity of the battery has to be "walled off" to protect the cells and becomes temporarily unavailable. The BMS takes account of the cell temperatures and scales the reported SoC on the dashboard to "hide" this missing capacity.

So if you had a battery that had say 25kWh usable capacity at 20C you might find that it only had 22kWh usable capacity at -5C while still staying above the minimum allowed cell voltages. As soon as the battery warms up the "missing" capacity is available again.

As long as you drive relatively conservatively I suspect the reduction of usable capacity with cold is more important than the reduced efficiency caused by higher internal resistance.

And both these battery effects are smaller than the increase in power consumption of simply trying to keep the car warm with the heater. If it's very cold dropping the cabin temperature a couple of degrees and turning the seat heaters on can make quite a difference to range especially on a Leaf where a low heat output can be managed by the heat pump while a high heat output calls upon the resistance heater as well.

As for what you can do about these various winter range loss mechanisms - plugged in preheating can save as much as about 2.5kWh (equal to about 8 miles range in winter) so is well worth doing, also if you use the charge time to delay charging until the early hours of the morning the charging of the battery just a few hours before you use the car will help warm the battery a few degrees.
That’s a great answer! 👍

I have noticed in my 40 Leaf that in the cold the first 10% SOC when started from very cold seems to disappear very quickly, after this I’m guessing the battery has warmed up and the charge percentage drops off much more slowly from there.

The heater makes a big difference, I think when starting from cold it uses a little resistive heater to help the heat pump first thing which uses more power.

I deliver locally in my leaf so make lots of short trips all day but if you only drive a few miles then park it an let it go stone cold again before driving home for example I can imagine that the “winter effect” is rather more pronounced.
 

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A quick fix on a cold morning is to bung in a rapid charge (from where I live there are motorway services about 8 miles into my commute), a quick 10 minutes rapid brings the battery temperature up which, as well as adding range by adding charge, also warms it up (and once you are driving it tends to stay warm partly due to its large thermal mass and partly because you are pulling power from it, even on a freezing day) which means it goes back to a "normal" capacity.
 

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The battery packs have quite a bit of thermal inertia, mileage drops further as any residual heat gets dissipated. I fully expect that you will notice a few more miles disappear as we get further into this cold snap.
with my 24 I could expect 90ish in the summer and 60ish in the winter. If you do lots of short journeys you can expect your total range to be lower as getting the cabin toasty from frozen takes about 5 or 6 miles range worth of energy each time that you do it.
As mentioned above if it becomes a problem a rapid charge is a good way of getting some warmth into the battery and if you have a garage use it!
 

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I have noticed in my 40 Leaf that in the cold the first 10% SOC when started from very cold seems to disappear very quickly, after this I’m guessing the battery has warmed up and the charge percentage drops off much more slowly from there.
Is that with or without plugged in preheating prior to departure ? Unless you're already using preheating, most of that initial rapid drop will be the power consumption of the heater running flat out getting the cabin up to an acceptable temperature. Keep an eye on the climate control power use meter on the zero emissions screen when you first start the car vs after it's up to temperature and you'll see what I mean.

It would take more than those first 10 miles of driving to warm the battery appreciably. In my entire 18 mile trip to work in the morning the battery temperature only rises a couple of degrees, and that's with half the journey on the motorway. Rapid charging increases the battery temperature far more than driving.
The heater makes a big difference, I think when starting from cold it uses a little resistive heater to help the heat pump first thing which uses more power.
It uses more than a little, it uses it a lot during initial warm up. :) I've posted about this in detail in another thread recently but the heat pump typically only runs at about 500 watts and rarely goes over 1kW, so the difference between that and the total climate control power consumption is the resistance heater. The resistance heater always runs during initial warm up and keeps running for quite a while depending on conditions and how high you set the temperature.

The balance of power between the resistance heater and heat pump can be monitored in Leafspy. On the power bar graph, and it's quite sobering how much the resistance heater still gets used.

I deliver locally in my leaf so make lots of short trips all day but if you only drive a few miles then park it an let it go stone cold again before driving home for example I can imagine that the “winter effect” is rather more pronounced.
Yes, lots of short trips with a long stop between them will decimate the range of an EV as that initial cabin warm up each time consumes a lot of power. I certainly notice my range is a lot shorter when my daily driving is broken up into 4 separate trips (a two part outbound journey with a short gap and a two part return journey with a longer gap) vs simply driving the same distance without stopping.

Not much that can be done about it unfortunately.
 

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There are quite a lot of similar discussions in ASHP house heating systems right now re needing (higher) heat output during colder weather from a heat pump. All models vary a bit and one quite key difference is the type of fluid used - this affects the ‘range’ of temps the fluid can usefully be used over and therefore the performance at the extremes (right now is an England extreme but miles away from being a proper extreme). Heat pumps harvest heat from the ambient air and so provide more output heat than the input electricity in kW. The ratio is lower as ambient drops.

In a similar way house heat pumps compromise in one of two ways - either they run for far longer and slowly warm the house (via weather compensation controls) or they switch in one or two immersion heaters. The latter is much more expensive as no heat is harvested from the air by the immersion(s).

In a car we typically don’t want the heat pump to slowly warm the cabin (or defrost) over several hours so in comes the resistance heater. Clearly you can use pre-heat while connected to counter this initial warm up load.

I suppose I’m saying ‘it is what it is’ and the parameters Nissan had to play with depend on the type of heat pump fitted.
 

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When the battery is much colder the internal resistance goes up increasing voltage drop for the same load and as a result it can't be discharged to as low a SoC under load without dipping below the minimum allowed voltage.

In essence some of the bottom end capacity of the battery has to be "walled off" to protect the cells and becomes temporarily unavailable. The BMS takes account of the cell temperatures and scales the reported SoC on the dashboard to "hide" this missing capacity.

So if you had a battery that had say 25kWh usable capacity at 20C you might find that it only had 22kWh usable capacity at -5C while still staying above the minimum allowed cell voltages. As soon as the battery warms up the "missing" capacity is available again.
I wonder if its possible to potentially land yourself in trouble, lets assume the following scenario;
You've been on a lengthy motorway blast (say 70miles in ~5C ambient)
The battery is warm due to the extended usage and the car is giving you all the allowed charge.
Now you reach your destination with less than 5% SoC, park overnight where the ambient temperature dips below freezing. Now the battery cells have a higher resistance than they did when you parked?
Could your 5% SoC suddenly be 0% when you put a load on the battery to set off in the car again?
Obviously this is a fairly unlikely scenario but could be possible?
 

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I wonder if its possible to potentially land yourself in trouble, lets assume the following scenario;
You've been on a lengthy motorway blast (say 70miles in ~5C ambient)
The battery is warm due to the extended usage and the car is giving you all the allowed charge.
Now you reach your destination with less than 5% SoC, park overnight where the ambient temperature dips below freezing. Now the battery cells have a higher resistance than they did when you parked?
Could your 5% SoC suddenly be 0% when you put a load on the battery to set off in the car again?
Obviously this is a fairly unlikely scenario but could be possible?
I would not leave the car parked overnight at 5% under any conditions. And yes you could get yourself into trouble doing that if you had a warm battery and left it to cool, however it would take more than just overnight for it to cool dramatically. A couple of days left unused, yes.

I really notice the difference in morning battery temperature if the Leaf hasn't been driven for a couple of days vs driving to work every day.
 

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Answering that in an obtuse way it’s never a good idea to leave an almost depleted battery out in the cold anyway.
I agree a terrible idea but it's entirely plausible an owner who doesn't know all the specifics and the do's and don'ts could end up in such a situation, although probably wouldn't be a common occurrence.
 

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I agree a terrible idea but it's entirely plausible an owner who doesn't know all the specifics and the do's and don'ts could end up in such a situation, although probably wouldn't be a common occurrence.
and that's why 100% is not 100% and 0% is not 0% on a car battery.
The car's BMS leaves quite a bit of charge in an unusable reserve to protect the battery, you can never really fully charge or deplete your car traction battery, its one of the reasons why they perform much better and for longer than the battery in your phone or laptop
 

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I inadvertently charged my 47,000 mile, twelve bar SoH, 24kWh Leaf to 100% yesterday evening. Normally it is set to limit charge to 80% so this hasn't happened before. Why it was allowed to charge to 100% is irrelevant but I had no need to use it this morning and the weather was so appalling that I didn't want to drive it to use the top two decades of percentage so I started it on my (secure and hidden) drive, left it 'ON' in park with heat and a/c on normally to deplete the extra charge level. Profligate, of course (sorry Greta!) but it scrubbed off the top 30% in only about two to two and half hours or so just sitting there. This demonstrates just how power hungry the 'hotel load' of heat, air conditioning, DRLs, fans etc really is. I should repeat the exercise with all things optional switched off as a comparison but I can already hear the screeching of the energy efficiency harpies as they circle overhead!
 
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