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Guys, I was wondering how many miles can we travel when the EV gets to reserve mode ?
I mean after a low battery warning pops up, how many miles can the car actually travel before we get to the next charging point? Does it vary from car to car or is there some common ground on this - Which is the best car in this context?
 

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I think you're trying to map gasoline engine concepts onto EVs. There's no 'reserve' as such. All EVs and PHEVs have some sort of battery range remaining indicate in front of the driver all the time. With PHEVs when that reaches zero, the petrol engine fires up. With BEVs the behaviour of the car as you get near battery exhaustion varies with model. Perhaps a Leaf owner can describe what it does before it finally grinds to a stop!
 

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The leaf has 2 warnings, after the first warning the car continues as normal, after the second warning the car slows down, you can not accelerate as much or get high speed (turtle mode) until the car comes to a halt. Your lights etc keep working (until the 12v battery is drained) but you can not 'start' the car back up.
 

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Zoe Devotee
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When you get down to --- you have to assume you have no more range, anything extra is a bonus if you've still got distance to your next charger.
 

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On Tuesday night, I went from 8 to -- on the range estimator and the battery read 8%. I had 3 miles until home, but one very big hill. I drove at 33 mph all the way home, at the bottom of the hill the battery indicated --% too.
I made it home with no tortoise (a turtle is a sea creature).
When I started the drive home, it was 29% and 29 miles. I was managing a mile per every percent.
I had scheduled a charge but I got stuck in traffic and I was getting more range as I was travelling slower than the 65/70 mph that I had anticipated. As I got nearer to home, I passed the charger with 15% and 15 miles left and 15 miles on the range estimator.
 

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LEAF:- from experience. at around 20 miles left the yellow triangle warinng light shows together with a loud 'Ping'. Quite quickly the guessometer goes into flashing mode. or bars not numbers. Suddenly more pings and the car goes into Turtle mode. It will only drive slowly, and not for very far. Then , in my case, after about a mile everything goes black. The car stops and you walk home.
In terms of 'reserve' that's what the yellow warning triangle and the 'Ping' is for!

You may have been misled by the safety margin built into the battery setup, this is to protect the battery not to give a 'get you home' reserve.
 

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I had a Gen1 Leaf. On that the "low battery" warning came on at 17% battery (from leafSpy) and with around 8-9 miles indicating on the range estimator. At that point the range remaining just flashed and still counted down okay.

I could usually get 5-6 miles more before any more warnings, with a range indicator of 3-4, at which point LeafSpy would usually show about 10% left so I suspect I could have squeaked another few miles after the very low battery warning (which is the point of power limitation)

Gen 2 leaf also shows low battery at 17% and flashes away, although generally for some reason I usually have 15-16 miles indicating at that point.

Haven't got to very low battery warning yet on the Gen 2.
 

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Zoe Devotee
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I made it home with no tortoise (a turtle is a sea creature).
.
Are you implying a turtle cannot move on land? They can.... slowly! So I think Turtle mode stands, plus the Leaf looks a bit like a turtle, especially when limping along in turtle mode. :p
 

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Are you implying a turtle cannot move on land? They can.... slowly! So I think Turtle mode stands, plus the Leaf looks a bit like a turtle, especially when limping along in turtle mode. :p
The looks are growing on me like algae, so I will succumb to your analogy.
 

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Here's a mini rant I wrote on the Tesla Owners FB Group a few weeks back. Almost certainly applies to other EV types too...

*** THERE IS NO RESERVE ***

A reserve is a known backup, where the car (or plane) has been designed to squirrel away a bit of fuel deliberately to provide owners with a get-out-of-jail free card in case they don't pay attention to their range and hit zero. This is pretty common with ICE cars and especially diesels where if you run out of fuel completely the whole system has to be bled and refilled and it's an enormous hassle (my old Audi A8 had a behaviour where once you get past 0 miles range showing the engine management system would start deliberately making the engine misfire in order to shock the driver into thinking they're running on fumes and to immediately get fuel!)

The Model S does not do this. Why would it - the single biggest criticism levelled against electric cars is that their range is too low - so the idea that Tesla would deliberately under-state the real range of their cars is crazy.

What does exist is uncertainty about how much usable charge remains in the battery, and since it would be a disaster for Tesla if the cars regularly shut down before they reach zero range, the algorithm that guesstimates when you are going to run out is naturally cautious, so that on average most people will not run out until somewhere after the 0 point. This is what leads to so many videos on youtube of people driving (sometimes for significant distances) beyond zero. But that's not a reserve, that's a set of error bars on the exact location of "empty". And there absolutely have been a few people who have had their cars shut down before they hit 0.

The Model S "runs out" of energy when the safety system designed to protect the pack kicks in. That happens as soon as the voltage of any of the individual modules within the pack drops below a defined value. This is a hard-coded protection mechanism that cannot be overridden: as soon as any cell drops below a certain voltage, the main battery contactor disconnects the whole pack in order to protect it from permanent damage. At that point you just coast to a halt, and the 12V system will keep powering the accessories for a little while until the 12V battery also discharges.

Since cell voltage varies depending on how much power you're drawing from the pack, this means that if you drive hard it's likely that one of the battery modules will drop below the shutdown voltage sooner than it would have if you drove gently. That's why the dotted lines appear in the dash power meter when you're low on charge - the car is limiting power to avoid the situation where you accelerate hard and the battery protection logic shuts the whole pack down even though there's quite a bit of charge still available.

So the car is cautious with its educated guesswork about how much energy is remaining in your battery pack, which means that on average when it reads 0 miles remaining there will actually be a bit more energy left. And assuming you're driving along a road where it is easy and safe to stop at any time you can happily keep going after it reads zero and benefit from the cautiousness of the software. But as Tesla get better at accurately predicting the zero point they will naturally start to reduce the size of the error bars, which means that over time it gets less and less likely that you will be able to keep driving for any significant distance after the car reads 0.

But this is all totally different to a petrol car where it's known for example that when the tank gauge hits empty, in practice all the fuel pipes, pumps, etc still have another litre or so of petrol inside them.

tl;dr there is no reserve :)
 

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Perhaps we need to have a fuel selector tap just like on aircraft - a second battery that the competent can physically turn to when the main tank gets to empty :)
 

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I always carry a gallon of petrol in my vehicles in case of emergency - this will get me 40 extra miles, more than enough to find a filling station.
What's the procedure in a BEV? Recovery to the nearest charging point and a 30 minute wait until charged?
 

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If I remember this correctly, the Volt has a sort of double reserve: when you run out of battery it switches to dinojuice, and if that runs out it switches back to battery in limp-along mode for another few miles. The first of these is of course normal running (almost every day for me), the second requires particular bravery or foolery to encounter.

If you want a description (and video) of the Leaf's behaviour when running out of battery, try Video: Nissan Leaf (Almost) Does a Tour Stage
 

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Zoe Devotee
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Here's a mini rant I wrote on the Tesla Owners FB Group a few weeks back. Almost certainly applies to all other EV types too...

*** THERE IS NO RESERVE ***

A reserve is a known backup, where the car (or plane) has been designed to squirrel away a bit of fuel deliberately to provide owners with a get-out-of-jail free card in case they don't pay attention to their range and hit zero. This is pretty common with ICE cars and especially diesels where if you run out of fuel completely the whole system has to be bled and refilled and it's an enormous hassle (my old Audi A8 had a behaviour where once you get past 0 miles range showing the engine management system would start deliberately making the engine misfire in order to shock the driver into thinking they're running on fumes and to immediately get fuel!)

The Model S does not do this. Why would it - the single biggest criticism levelled against electric cars is that their range is too low - so the idea that Tesla would deliberately under-state the real range of their cars is crazy.

What does exist is uncertainty about how much usable charge remains in the battery, and since it would be a disaster for Tesla if the cars regularly shut down before they reach zero range, the algorithm that guesstimates when you are going to run out is naturally cautious, so that *on average* most people will not run out until after the 0 point. But that's not a reserve, that's a set of error bars on the exact location of "empty". And there absolutely have been a few people who have had their cars shut down *before* they hit 0.

The point at which the pack shuts down is determined by when the voltage of any of the individual modules within the it drops below a defined value. This is a hard-coded protection mechanism that cannot be overridden: as soon as any cell drops below a certain voltage, the main battery contactor disconnects the whole pack in order to protect it from permanent damage. At that point you can simply coast to a halt, and the 12V system will keep powering the accessories for a little while until the 12V battery also discharges.

Since cell voltage varies depending on how much power you're drawing from the pack, this means that if you drive hard it's likely that one of the battery modules will drop below the shutdown voltage sooner than it would have if you drove gently. That's why the dotted lines appear in the dash power meter when you're low on charge - the car is trying to avoid the situation where you accelerate hard and the battery protection logic shuts the whole pack down even though there's quite a bit of charge still available.

So the car is cautious with its educated guesswork about how much energy is remaining in your battery pack, which means that on average when it reads 0 miles remaining there will actually be a bit more energy left. But as Tesla get better at accurately predicting the zero point they will naturally start to reduce the size of the error bars, which means that over time it gets less and less likely that you will be able to keep driving for any significant distance after the car reads 0.

That's totally different to a petrol car where it's known for example that when the tank gauge hits empty, in practice all the fuel pipes, pumps, etc still have another litre or so of petrol inside them.

tl;dr there is no reserve :)

With the Zoe there kind of is a reserve. It counts down the miles until you get to 5 miles then goes to ---, after those 5 miles it goes into Limited performance mode, limiting you to 16kw of power, which is good for 30mph, for what distance I don't actually know, certainly at least 1 mile as that's about the distance I covered to my charger.
 

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@mgboyes Personally, I bring my Scuba experience to EV driving.

Like Scuba cylinders (though of course the risk of running out is far more serious) I too view 0 as zero. I also see zero as not a target, but an emergency situation.

Two reasons for this:
1) It's always good to have contingency
2) The gauges aren't 100% accurate at lower pressures, or in EV terms the estimate is more inaccurate at low SOC.

Whilst I know there are others that are happy going to <5 miles, it's not for me. So even if there was a hidden reserve I'd not be using it.

As a bit of side trivia, the Audi system reminded me a little of old fashioned Scuba cylinders :)

"J" Valve

The idea was you would find it difficult to breathe when the cylinder got close to empty, and you'd pull the lever to allow access to the final reserves of the tank, then make your way to the surface.

Unfortunately they would get knocked or people would forget to set them correctly at the start of the dive, in that case you'd pull the lever only to find you had no reserve. You were then S.O.L.

So now good practise is to use a gauge, and surface with 50 bar left in the cylinder (which is 1/4 of a typical fill) You have contingency, and you avoid low level inaccuracies. Carrying this over to EV driving I use a more cavalier 10% buffer (20 miles), but then the consequences of running out are far less serious ;)
 

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I took heed from this post and last night whilst driving back from the Arsenal game :), we stopped for a rapid charge. I could have made it home with an estimated four miles in reserve, but chose to stop for a toilet break and to fill the kids up so that I wouldn't need to cook when I got home.
 

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The Leaf has 2 warnings... the Low Battery Warning (LBW) at about 18% and the Very Low Battery Warning (VLBW) at about 10%. At both these warnings there is a visual warning and a audible warning but nothing changes as far as the performance of the car goes. At some point after that (and I can't remember what the % is as it has only happened to me a couple of times) the Turtle shows and the car then slows... first to 30 mph max then even slower until it stops.

So, you do not need to take emergency action at the LBW or VLBW but at the VLBW I would start to look for somewhere safe to stop. If you ever get to Turtle then you have yards to go not miles so pull over and stay safe.

What's the procedure in a BEV? Recovery to the nearest charging point and a 30 minute wait until charged?
Yup... that is pretty much it... except that it might be a 30-60 min wait to start charging if there is a queue and then a 30 mins charge yourself... not to mention the 2hr wait for the flat bed truck to turn up. That is why I don't do many long trips in my EV any more.
 

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On the Soul there are options for reminders which you can customise, which can vary from almost no warnings to complete nuisance interruptions. I choose 'almost nothing'. There is also a low battery 'icon' in the instrument cluster which lights as follows:
upload_2015-11-30_22-56-36.png

I have put a link to the Soul Handbook in the Soul EV threads of SpeakEV. At 10% of usable battery the range goes to "--" but at that point there are 5-15km of range left, depending on conditions(according to handbook). Our range at the mo is about 95, so 10% is about 9 miles, whereas the summer range was easily 110, (sometimes much more) so 10% must be about 11 miles. The range indicator is always conservative but like other posters say, you don't want to leave it too late. We will stretch it if we are near home. If you are thinking of long trips in a battery EV, the range of each section can be limited to 80% of range minus the 'low' you are prepared to accept (apart from the first section after a 100% charge). Most of us plan to stop at the charger before the one we really need, in case one is broken. We have done 77 miles from 80% to reach home though. Basically, we have learned to trust the car, but not the chargers (not completely anyway)
 
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