NiMH and my Leaf

[surfingslovak]

i suspect you will be proven wrong. i predict "some" LEAFs will see 120-150,000 miles by the time they reach 30% degradation. granted not all will, but then again, not all RAV 4 EV NiMH battery packs did well either

Glad to be proven wrong. The total mileage question aside, reports of 10% range loss from many drivers across what could be considered moderate climes after year and a half, is not what some would consider good longevity. Given what Steve Marsh is reporting at 55K miles in the ideal battery climate of Kent, WA, I don't think that we will ever see a 150K Leaf with 70% capacity remaining. Not unless you or Mark Larsen pulled some magic with numbers. In that case, nothing would surprise me.

 

[DaveinOlyWA]

i suspect you will be proven wrong. i predict "some" LEAFs will see 120-150,000 miles by the time they reach 30% degradation. granted not all will, but then again, not all RAV 4 EV NiMH battery packs did well either

Glad to be proven wrong. The total mileage question aside, reports of 10% of range loss from many drivers across what could be considered moderate climes, is not what some would consider good longevity. Given what Steve Marsh is reporting at 55K miles in the ideal battery climate, I don't think that we will ever see a 150K Leaf with 70% capacity remaining. Not unless you or Mark Larsen pulled some magic with numbers. In that case, nothing would surprise me.

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ya, i ran some guesstimates on his degradation and came up with two figures both running him over 100,000 miles at 30% degradation.

even if we take his worst figures. he had use of a GID meter which showed him charging to 243 at full. if his degradation remains constant he is losing a GID every 1400 miles or so. if 30% degradation is losing 84 GID, he would hit that at 120,000 miles if his loss is linear from here.

now, the consensus is loss is a bit quicker at first then levels off. what we dont know is

1) when the degradation starts because it does not start right away so the above calculation "could" be way off

2) whether his rate of degradation is leveling off or still on the "upswing" although i STRONGLY suspect most of his range loss is due to the change in weather.

 

[surfingslovak]

now, the consensus is loss is a bit quicker at first then levels off. what we dont know is

1) when the degradation starts because it does not start right away so the above calculation "could" be way off

2) whether his rate of degradation is leveling off or still on the "upswing" although i STRONGLY suspect most of his range loss is due to the change in weather.

Yes, the weather plays definitely a role, and the Gids/mile reported are consistent with the reported energy economy. I don't understand that in your case, when you see 281 Gids indicated in similar climate, then this must be accurate and represent no loss of capacity, but in Steve's case the Gid count must be inaccurate, and also represent more capacity. What kind of logic is that?

I don't want to get into another argument over the behavior of this car, and how to interpret observed results. We had plenty of that. I'm well aware of the fact that until we can read the battery state of health from the CAN bus, there will be always someone who wants to believe something and will try to prove their bias.

Please understand that I have no axe to grind, and if the battery pack will turn out to be long-lived, I will be very happy to hear it. All I wanted to say in my post above is that we should not let our current impressions and expectations color what we think of lithium ion batteries in general. No need to get defensive. And with that, I'm going to wish you a good evening.

 

[DaveinOlyWA]

now, the consensus is loss is a bit quicker at first then levels off. what we dont know is

1) when the degradation starts because it does not start right away so the above calculation "could" be way off

2) whether his rate of degradation is leveling off or still on the "upswing" although i STRONGLY suspect most of his range loss is due to the change in weather.

Yes, the weather plays definitely a role, and the Gids/mile reported are consistent with the reported energy economy. I don't understand that in your case, when you see 281 Gids indicated, then this must be accurate and represent no loss of capacity, but in Steve's case the Gid count must be inaccurate, and also represent more capacity. What kind of logic is that?

I don't want to get into another argument over the behavior of this car, and how to interpret observed results. We had plenty of that. I'm well aware of the fact that until we can read the battery state of health from the CAN bus there will be always someone who wants to believe something and prove their bias.

Please understand that I have no axe to grind, and if the battery pack proves to be long-lived, I will be very happy to hear it. All I wanted to say in my post above is that we should not let our current impressions and expectations color what we think of lithium ion batteries. And with that, I'm going to wish you a good evening.

i am not disputing what you are saying and i agree its way too early in the game to make any definitive conclusions concerning longevity of these packs. however, the general consensus seems to be that there is no future for many LEAF owners unless they can get replacement packs which i am sure they will be able to do and yes there will be people who need replacements sooner due to greater driving need

and i dont generally post to argue. mostly to see if my logic is valid (which can be shaky at times) which means sometimes i post hypothetical thoughts and statements. its that reason that i do value anything you have to say

 

[kubel]

Nilar.

</Large format NiMH patent encumbrance conspiracy theory>

 

[TonyWilliams]

"Super-light magnesium alloy wheels and seats provided strength despite their low weight.... Magnesium wheels are light wheels, much lighter than steel or aluminum wheels. That means they will give better mileage for your car because there's less weight to move. The main factor weighing against magnesium wheels is the price. They're expensive.

Well, they are also DANGEROUS!!! Imagine a fire with you sitting in a magnesium seat; what puts that fire out?

Burning magnesium dissociates water so as to combine with the oxygen, so water won't put out a magnesium fire. Magnesium combines exothermically with water and actually INCREASES the fire with more oxidizer (the O in H2O).

How many fire departments will know that, while they are lighting you up with water?

 

[jlsoaz]

I have now had my Leaf for 16 months with about two years left on my lease. As long as I have charge in the battery, I am very well pleased with the car. However being on the cautious side, I am uncomfortable attempting a trip of more than 60 miles although I have gone farther. My problem is not range anxiety but what I call range lust, the car meets my basic needs but I just want to hit the road and keep driving.

The expiration on my lease will come at about the time that another event will occur, the NiMH battery will come out of patent. We know that both the EV1 and Toyota RAV4 Electric had true ranges of over 100 miles. If someone would bring out a NiMH powered electric car, I think that I would buy it rather than get another Li powered car. We know that NiMH batteries are very dependable and by now manufacturing costs should be down quite a bit. A car like the EV1 which just everybody loved could probably be built today to sell for less than $20,000.

I should be interested in the thoughts of others about this.

I'd like to see more competition and let there be a judgment in the marketplace as to whether NiMH EVs would be a good solutions to the severe range limitations of some of the LiB Evs. I question if this will happen since the body language of the major auto oems seems to be (any exceptions?) anti-NiMH for traction batteries for plug-in vehicles. I don't know if this is attributable to persistent soto voce legal pressure against NiMH, or they simply think LiB is the better technology, or what.

There are some excellent LiB PIVs that will go well beyond 100 miles, though for now they are $50k and above.

There are also a few hard-to-discern wildcards on the battery maker side, including BASF (which bought Ovonic I believe), GP Batteries, Johnson Controls, Varta, SAFT and Hunan Corun.

Since the Chinese have only half-respect for international patents, I have been wondering if there is to be any breakout in actual real-world competition in batteries if it might come from them. We know sometimes they seem to beat their heads against the Lead-Acid battery side of things.... why not try NiMH? Hunan Corun is a wild-card in this respect.

In the end, I think a lot of us are hoping that LiB will work out, and there are reasons to believe that it will (including in the areas of battery longevity and high gross onboard kWh). The vehicles that Tesla is putting out are in my view kind of mind-blowing and if their approach to TMS turns out to deliver on good battery/range longevity, then maybe this will render somewhat moot the NIMH question.

Still, I think it is a good suggestion that there should be an open global competition (however overdue) and let the market decide based on real-world empirical buyer experiences and decisions rather than based on technology suppression and resultant not-completely-open-competition. I think the market will likely decide on LiB, but how about making sure that there is in fact competition?

I do not know with absolute certainty that the apparently repressive patent situation will be fully alleviated soon. Are you certain of this?

I was re-reading the RAV4 EV forum recently and someone said something about more modern NIMH technology. Does anyone know what was meant by this? Have there been important recent innovations?

I think some 2000s-era NIMH evs had the same range degradation problems that some 2010s-era LiB evs have but this was not as widely discussed. I don't know how the percentages compare. Example: I once test-drove a RAV4 EV in 2002 or so in SoCal and the dealer told me that he had one or two buyers who were EV1 drivers who had suffered such severe range degradation that it was kind of a no-brainer. This may not have been the whole story, but the comment stuck with me.

 

[surfingslovak]

Example: I once test-drove a RAV4 EV in 2002 or so in SoCal and the dealer told me that he had one or two buyers who were EV1 drivers who had suffered such severe range degradation that it was kind of a no-brainer. This may not have been the whole story, but the comment stuck with me.

Interesting, I've heard that some of the early EV1s had lead-acid batteries. There was talk of some pretty serious battery problems that were resolved after GM switched vendors. Not sure if this extended into the NiMH era. ElectricVehicle would be a good guy to ask about that.

Well, they are also DANGEROUS!!! Imagine a fire with you sitting in a magnesium seat; what puts that fire out?

Burning magnesium dissociates water so as to combine with the oxygen, so water won't put out a magnesium fire. Magnesium combines exothermically with water and actually INCREASES the fire with more oxidizer (the O in H2O).

How many fire departments will know that, while they are lighting you up with water?

Interesting, haven't thought of that! SAE seems to think that alloys with certain chemistries might be permitted in aircraft applications. I wonder if GM used an alloy that was potentially quite hazardous. Looks like the tech in the EV1 was really pushing the envelope.

 

[TEG]

http://en.wikipedia.org/wiki/Alloy_wheel" onclick="window.open(this.href);return false;

Magnesium alloy wheels

Magnesium wheels were the first die-cast wheels produced, and were often referred to as simply "mag wheels." However, true magnesium wheels are no longer produced, being found only on classic cars. Magnesium suffered from many problems. It was very susceptible to pitting and corrosion, and would start to break down in just a few months. Cracking was a common problem, and the wheels were very flammable. Magnesium is used for flares and early flash lamps. Magnesium in bulk is hard to ignite but, once lit, is very hard to extinguish, being able to burn under water or in carbon dioxide, which are common extinguishing materials. Tires that caught fire could soon ignite the magnesium, creating difficulties for fire responders. Magnesium wheels required constant maintenance to keep polished. Alloys of magnesium were later developed to help alleviate some of the problems.

Magnesium wheels were originally used for racing, but their popularity during the 1960s lead to the development of other die-cast wheels, particularly of aluminum alloys. The term "mag wheels" became synonymous with die-cast wheels made from any material, from aluminum alloy wheels to plastic and composite wheels used on items like bicycles, wheelchairs, and skateboards.

Magnesium alloy wheels are sometimes used on racing cars, in place of heavier steel or aluminum wheels, for better performance.

 

[TEG]

Interesting, I've heard that some of the early EV1s had lead-acid batteries. There was talk of some pretty serious battery problems that were resolved after GM switched vendors. Not sure if this extended into the NiMH era. ...

Yes, some EV1s had Lead-acid batteries that didn't last very long.
I think there were some battery cooling issues with the first batch of EV1s too.

The Ford Ranger EV truck also came in lead-acid and NiMH versions.

The lead-acid versions tended to need new battery packs every few years. Lead-acid doesn't have very high cycle life when deep cycled.

The EV1 was using Ovonic NiMH, and the (Toyota) RAV4EV + (Ford) RangerEV + (Honda) EVplus all used Panasonic NiMH.
During the Ovonic (Texaco/Chevron) vs Panasonic litigation, Panasonic claimed that they revised/improved the NiMH chemistry such that it should no longer be considered similar enough to be covered under the Ovonic patents. Well, they lost that battle, and were kept off the market in the USA, but the ones that did get here before seem to hold up much better than the Ovonic versions.
Many Ford Ranger EV & Rav4EV Circa year 2000 are still working with their Panasonic NiMH batteries.
The EV1s were recalled/crushed, so hard to compare, although there are a handful of Chevy S10 EV pickups still around with (I think) Ovonic NiMH batteries, so I suppose someone could compare the degradation of S10 EV packs to Rav4EV packs to compare the long term differences.

By the way, BatteryMD probably knows a lot about the differences between these different NiMH batteries.
http://www.batterymd.com/projects.html" onclick="window.open(this.href);return false;

 

[elmobob]

Several people have pointed out the weight advantage of Li. I don't see how it matters when the EV1 and Toyota RAV4 Electric had much greater ranges than the Leaf. Moreover my Prius sat out in the Arizona sun for ten years and this did not affect the battery efficiency. If GM wanted to serve the country, it would either build the EV1 again or sell the plans to another company that would. The EV1 was also a more beautiful car than most.

With NiMH there is more data on how it's expected to perform however we cannot come to the conclusion that NiMH Ovionics chemistry is better than what's on the leaf because on a prius for example the 1.2 KW is only discharged very gently, if you notice you have to feather it to stay in EV plus its only charged to 80% max and discharged to 40% max. If you where to have this same NiMH battery chemistry on the leaf and draw 80KW+ peak for short periods of time periodically and use it close to it's full capacity I'm sure you'll experience just as high level of degradation. I will agree that NiMH batteries from current available data have proven to not be as sensitive to heat as the current chemistry of batteries on the leaf, but if Nissan had put active cooling on this battery this would not be an issue however it would have resulted in an increased price + decreased available range.

 

[surfingslovak]

The battery pack in the Prius is quite large, and it weighs a ton. This is not a fair comparison, but if Leaf's pack had the same weight density, we would only have about 6 kWh total capacity. If we only used 20% out of that in a 40 to 60% SOC cycle, then that's about 2 kWh usable.

The traction battery is a sealed 38-module nickel metal hydride (NiMH) battery pack providing 273.6 volts, 6.5 A·h capacity and weighing 53.3 kg (118 lb)[112] is supplied by Japan's Panasonic EV Energy Co. They are normally charged between 40–60% of maximum capacity to prolong battery life as well as allow headroom for regenerative braking. Each battery pack uses 10–15 kg (22–33 lb) of lanthanum, and each Prius electric motor contains 1 kg (2 lb) of neodymium; production of the car is described as "the biggest user of rare earths of any object in the world."

The 1st-gen RAV4 EV did pretty well, based on anecdotal reports at least.

The RAV4 EV has 24 12-volt 95Ah NiMH batteries capable of storing 27.4 kWh of energy. (Total weight about 1,000 lbs.)

The RAV4 EV's battery system is a consumable item. Toyota reports that battery pack replacement costs are currently higher than the value of the used vehicle. Toyota tested the RAV4 EV in Japan for 300,000 miles (480,000 km) over two years before introducing the vehicle in the United States. The economies of scale are affecting the replacement cost of the RAV4 EV.

Darelldd has lots of interesting data on his page. A Leaf-sized pack would have about 16 kWh total rated capacity if it had the same weight density.

On August 23, 2004, my Rav4EV had a "battery event." Nobody knows exactly why, but at 32% SOC, my car shut down after briefly showing a low module voltage in the 4V range. The battery ECU was initially swapped for a new one, and two modules were going to be replaced next. Although the suspect modules tested OK for capacity - after a day of sitting, my dealer's EV tech was not happy with how they responded.

Panasonic NiMH battery for RAV4 EV traction pack:
2002 Part number: G9280-42012 (random price assigned as $4700 in 2008)
Type EV-95

Nominal Voltage 12V
Nominal Capacity 95Ah
Specific Energy 63Wh/kg
Specific Power(D,O,D=80%) 200W/kg
Dimensions (mm) 116(W) X 175(H) X 388(L)
Weight 18.7kg = 41.2 lbs

RAV4EV 288v pack (24 x 12v x 95ah = 27.3kWh)

 

[TEG]

My NiMH RangerEV has the same Panasonic EV95 batteries, but 25 of them (instead of like 24 in the RAV4EV).

 

[EVDRIVER]

The battery pack in the Prius is quite large, and it weighs a ton.

I was not aware the Prius pack was more than 3X the weight of the LEAF pack :lol:

 

[DaveinOlyWA]

It's too early to tell for EVs but for my power tools and other electronic devices, Li has lasted much better than NiMH...

Part of that might be for ironic reasons. I think many cheap power tools had limited or a total lack of cell balancing and management. You can sort of get away with out that on NiMh. But Lithium absolutely requires it. And so I think a lot of power tools have dead batteries because people would keep using the things until they just stopped working and had no choice but to recharge the battery. Where most of the lithium devices these days will actually monitor the cells and force the device to stop working at a certain depth of discharge.

i actually read a really good article about power tools and batteries a few years ago (in magazine in doctors office) and the real reason for the better Li performance is the actual tool itself being much more efficient.

also Li being lighter means the batteries can be made lighter (#1 complaint for power tools) and have more cells increasing voltage which means better torque

 

[DaveEV]

The battery pack in the Prius is quite large, and it weighs a ton. This is not a fair comparison, but if Leaf's pack had the same weight density, we would only have about 6 kWh total capacity. If we only used 20% out of that in a 40 to 60% SOC cycle, then that's about 2 kWh usable.

That's really the key there - in the Prius the battery can degrade a significant amount and you don't even notice unless you drive in situations where you really push the pack to high and low states of charge (very hilly driving, for example).

 

[Nubo]

Nilar.

Vaporware.

 

[jlsoaz]

Some quick notes:

The EV1 had 3 batteries.

AC Delco Lead-Acid (cruddy I guess)
Panasonic Lead-Acid (good reputation, preferred by some over NIMH I guess)
Ovonic NiMH

If I recall, there was some talk of revisions to the charging aspect of the EV1 (the NiMH variant?) to account for running some cooling when it was charging? The efficiency or inefficiency of the charging process was of some interest. I have no recollection of this being mentioned with the NiMH RAV4 EV, but it is a broad thing to keep in mind that different batteries may have this or that somewhat-more-obscure issue to be aware of, sometimes manufacturer-specific, sometimes not.

 

[DaveinOlyWA]

i suspect you will be proven wrong. i predict "some" LEAFs will see 120-150,000 miles by the time they reach 30% degradation. granted not all will, but then again, not all RAV 4 EV NiMH battery packs did well either

Glad to be proven wrong. The total mileage question aside, reports of 10% range loss from many drivers across what could be considered moderate climes after year and a half, is not what some would consider good longevity. Given what Steve Marsh is reporting at 55K miles in the ideal battery climate of Kent, WA, I don't think that we will ever see a 150K Leaf with 70% capacity remaining. Not unless you or Mark Larsen pulled some magic with numbers. In that case, nothing would surprise me.

i talked with Steve today and I misunderstood his post. he is actually finishing his commute at or near VLB frequently. so he has 24 less GID to work with than i thought which means he might not make it during the colder days of this winter without slowing down or something. i let him borrow my SOC meter so he will be collecting data and we should have a better idea of where he is at.

 

[TEG]

I think it is established that NiMH is not as efficient in charging. You lose a higher % of your input power when charging. So, where overall efficient use of power is a goal, I think Li-Ion beats out NiMH there. NiMH is also said to have more "self leakage" where a vehicle left parked for extended periods will self-drain.

Possible benefits to NiMH could be in calendar life, safety, and possibly power density.
(But you have various Li-Ion chemistries that can vary in those attributes already.)