Reserve tank

We haven't heard yet what % of the available battery will actually be used, but it will be less then 100% - draining down to a low of probably 20% or so.

It would be nice to be able to use the rest of that charge in an emergency situation - even if it meant some degradation of battery performance as a result.

If the battery charge range is 20% to 80% - that means that 60% of the capacity should give you 100 miles, or the remaining 20% would be a reserve of about 33 miles. That would be more then enough to get you out of a bad situation - like running out of juice on a highway, or a two laner with no shoulder to pull off onto.

My understanding from reading about the Prius is that charging the battery to 100% full, and then running it down to 0% full *may* result in earlier battery degradation - I'm sure others here know more about the specifics then I.

Has anyone heard what happens to the car when you "run out of gas"? Does it just suddenly completely shutoff, or is there some type of more graceful failure mode?

LakeLeaf said:

Has anyone heard what happens to the car when you "run out of gas"? Does it just suddenly completely shutoff, or is there some type of more graceful failure mode?

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I don't have the direct information for you, but I remember reading that the car will first go into "Eco mode" when you hit the range limit. My guess is if you continue to push the car while in Eco mode that it will eventually just shut down.

We don't have details on Eco mode yet, but we speculated on what that was here: http://www.mynissanleaf.com/viewtopic.php?f=8&t=352&start=32

Pobably the "100" LA4 miles is 90% to 10% of the pack, or of the weakest cell in the pack.

LakeLeaf said:

We haven't heard yet what % of the available battery will actually be used, but it will be less then 100% - draining down to a low of probably 20% or so.

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I believe 24kWh is the usable amount of the pack. Otherwise we are in huge trouble. The Mini E has a "35kW" pack offering 28kW of usable storage...

If the Leaf's pack has, say, 19.2kW usable capacity, 100 miles is totally unrealistic even in the best circumstances. Of course, this is what the Leaf's detractors keep saying. I hope they're wrong.

I hope Nissan can stay away from marketing BS.

Pushing past the "normal" limit requires some serious deliberation. You can cause degradation, or even permanently damage the pack.

Tesla, for example, gives the owner certain options in this regard, along with warnings. I've heard of others (forget which), where the owner contacts the manufacturer to get the ability to extend the discharge. I imagine the conversation includes warnings and confirmation that the owner understands the potential consequences. It'll be interesting to see how LEAF handles this.

LakeLeaf said:

We haven't heard yet what % of the available battery will actually be used, but it will be less then 100% - draining down to a low of probably 20% or so.

It would be nice to be able to use the rest of that charge in an emergency situation - even if it meant some degradation of battery performance as a result.

If the battery charge range is 20% to 80% - that means that 60% of the capacity should give you 100 miles, or the remaining 20% would be a reserve of about 33 miles. That would be more then enough to get you out of a bad situation - like running out of juice on a highway, or a two laner with no shoulder to pull off onto.

My understanding from reading about the Prius is that charging the battery to 100% full, and then running it down to 0% full *may* result in earlier battery degradation - I'm sure others here know more about the specifics then I.

Has anyone heard what happens to the car when you "run out of gas"? Does it just suddenly completely shutoff, or is there some type of more graceful failure mode?

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i am not sure we will have a reserve like gas cars do. as an owner of an EV i can tell you, u dont just stop when u run out of electricity. batteries simply dont work that way. they simply start to lose power. if you are on the freeway, u will simply start to slow down. keep in mind, that running the batteries down to that point will probably shorten their life. Nissan may have software that would prevent u from going to far by simply shutting the vehicle off before it goes to far. but the slowdown process will happen before that point.

as far as the Prius; its range of charge runs from 40 to 80%.

This reminds me of a story somebody told me once, and this may be total BS, that there are stops on the throttles on planes (it was the 747 in this telling of the story) that you can "push through" and get like 115% of the max rated power, but if those stops are broken you have to overhaul the engines.

Nubo said:

I've heard of others (forget which), where the owner contacts the manufacturer to get the ability to extend the discharge. I imagine the conversation includes warnings and confirmation that the owner understands the potential consequences.

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Reva - in their upcoming car.

Page 14 of the "Product Uniqueness" .pdf shows all 24kwh available with the "empty lamp" coming on a 4kwh. From that, contrary to what one might expect, it looks like the entire battery capacity is available for use. :shock: Maybe with reduced performance when using that last 4kwh? :?

I noticed the level 2 charge is now 3.84kW up from 3.3kW... not much but I'll take it!

240 volts x 16 amps is 3830 watts, or 3.8 kW.

It is possible thay one might get only 3.3 kW actually to the battery (15% loss).

garygid said:

240 volts x 16 amps is 3830 watts, or 3.8 kW.

It is possible thay one might get only 3.3 kW actually to the battery (15% loss).

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But they also now say 7 hours instead of 8 to charge from empty?

Ok, 3.5 kW x 7 hours = 24.5 kWh is possible (only about 9% loss).

Some extra time might be needed (or used) for cell equilization (balancing) at a very low charge rate.

So far, I believe, we have not heard anything about the very important subject of cell management inside the battery pack (and we might not).

Did you overlook that they specified "about 7 hours" as being from "empty lighted to full charged", where empty lamp light is at 4kWh remaining out of 24?

(20kWh) / (7hr) is quite a bit less than 3.3kW, so how about this:

3.3kW * 7hr = 23.1kWh
- 13.5% loss: 3.1kWh
Net charge: 20kWh

Yes, I missed the "almost" empty part, Thanks.
7 hours for an almost full charge, and 8 hours for a full charge.
Sounds plausible.

Bicster said:

I believe 24kWh is the usable amount of the pack. Otherwise we are in huge trouble. The Mini E has a "35kW" pack offering 28kW of usable storage...

If the Leaf's pack has, say, 19.2kW usable capacity, 100 miles is totally unrealistic even in the best circumstances. Of course, this is what the Leaf's detractors keep saying. I hope they're wrong.

I hope Nissan can stay away from marketing BS.

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Why are you so worried, and why do you think that you'll be in huge trouble if the car only has 19.2kWh of usable capacity?

In A 19.2kWh pack should be enough to achieve the 100 mile LA4 rating. My Mitsubishi i-MiEV is a smaller car than the LEAF, but has similar performance and a 16kWh battery. In the last few days I've achieved a 90 mile range on a single charge. I know of other (again, smaller) electric cars with 12kWh batteries that can comfortably travel 75 miles on a single charge, whilst last year I was involved with a van manufacturer who was achieving 100 mile range on their 3.5 tonne van using 28kWh of lead acid batteries (usable capacity, 21kWh).

Ultimately, simply comparing kWh ratings of different batteries in different cars tells you nothing. There are so many different variables. It's a bit like measuring the cubic inches capacity of an engine to determine performance: if you take nothing else into consideration, the numbers mean nothing. With battery technologies, you need to take into account voltages, charge and discharge characteristics, ambient temperatures and temperature degradation, the power management system and the chemistry of the batteries themselves.

I'm not even entirely sure why the manufacturers bother to print kWh ratings for their batteries. They may as well publish the inside leg measurement of their CEO.

Back to the original question about reserve. With the Mitsubishi, the car does have a reserve tank - when the car tells you that you have '0 miles' left, you can continue driving for a few miles afterwards, eventually going into a 'limp home' mode at reduced speed before the car stops.

It's a similar situation with the G-Wiz, although if you really push the car to the limit, you can cause damage the batteries. The manufacturer does provide the dire warnings, and the car does go into limp home mode to protect the batteries. However, if you drive into the 'red zone' on more than two occasions, you will void the warranty on your batteries.

With the new REVA NXR, to access the reserve tank you have to send an SMS from your phone. The condition of the batteries is then remotely analysed and an additional charge is then released into the batteries in order to allow you to continue your journey. REVA say that there will be no degradation to the batteries as a result, because they remotely analyse the batteries to ensure the batteries are okay first.

This is interesting:

"Though automakers like to claim range in ideal circumstances, a better estimate may be to recognize that, today, range equates to around three or four miles per kWh of battery. Applying this formula to the Nissan Leaf with a claimed range of 100 miles and a battery with a 24 kWh rating would give an actual range between 72 and 96 miles."

http://green.autoblog.com/2010/06/13/concerns-continue-to-swirl-over-true-range-of-electric-vehicle/

100 miles on 19.2 kwh is not "totally unrealistic" that is just over 5 miles per kwh which is what my Zenn does on a VERY inefficient system and trust me on this; a Zenn is hardly something to model after. it was good for its time, but that time has long since past.

after hearing the curb weight, battery pack weight, etc. i have to think that pack is more than 24 kwh and maybe the usable charge is that. that could give a careful driver 120 miles or more.

either way, i am still excited, cant wait.

1. You CAN NOT charge the Prius battery to 100%, the computers will cut off charging. Well, maybe if you take it to Toyota AND they have one of the rare traction battery chargers. Even then, I will bet money it won't go over 80% (full 8 bars) and possibly only to 6 or 7 bars. The car 'lives' between 4 and 6 in normal driving, 3 and 7 not uncommon and 1, 2 and 8 are relatively rare. I wish there was a way to charge it to 8 at home on a regular basis. Starting 'full' would help overall MPG. But they like to leave 'head room' and besides, no one would want to plug in their car (or so Toyota thought).

In fact, if you go a big down will and it is re-genning to 'full bars', the engine will start and pull electricity out of the battery. Happened to me once. Stopped at a red at the bottom of the hill and the ICE kept starting and stopping. If I hadn't read about it ahead of time I would have been most concerned. The sad part is I was at the bottom of the hill and going to get on the Interstate. Hurts to waste electricity I would be using soon. But, of course, the computers don't read the driver's mind.

2. Don't know about the EV1 but Prius battery state is totally computer controlled. If you are out of gas and then drag it down to empty (40%) , it won't just start slowing down like a battery operated toy. Borrowing from Monty Python: It isn't 'dead', it is 'sleeping' I'm sure the Leaf will be the same because otherwise you COULD destroy a very expensive battery. But I agree, it would be REALLY GOOD if there was a 'open the reserve tank' switch like motorcycles have (or at least the little Honda 175 I had 35 years ago). It doesn't have to be 20 miles of range, but maybe a few miles. Enough to get off the Interstate even if you can't make it to a charging station.

bruceha2000 said:

... But, of course, the computers don't read the driver's mind.

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Not yet !