Clarity Fuel Cell

Pushmi-Pullyu said:
Well... there could be a danger of "explosion" in the sense of rapidly expanding gases -- and not in the sense of a fiery inferno -- if the seal on the pressurized hydrogen system was breached. But it's not like hydrogen is toxic. Hydrogen is (as most of us know, from high school chemistry class) dangerous if it's mixed with oxygen; when the oxygen level reaches ~25%, it becomes explosive. But without knowing more about fuel cell systems, based on just common-sense reasoning and what I know about the dangers of hydrogen explosions (less significant than the Hindenburg disaster suggests), my guess is that shouldn't be a significant danger unless the tank seal is breached. Seems to me that so long as the service area is well ventilated, there should be no problem with explosive hydrogen gas building up in the service area.
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You're a bit off on the 25% LEL limit of Hydrogen there--it is potentially explosive in air in any mix between around 4% and 75%. It's one of the widest ranges of any gas, which is one of the reasons it warrants caution if there is a leak in an enclosed area.

As you say, though, the actual risk of explosion is quite low in most real world situations, because H2, being a tiny molecule and extremely light, is very good at not building up a concentration--it will escape quickly into the upper atmosphere if outdoors, and even in most closed spaces. If a plume from a leak does catch on fire you just get a jet of flame. The only risk is if you build up a cloud in an enclosed space.

Here is a video (made many years ago) of a vehicle with an H2 tank that was opened and lit on fire--big jet of flame at the point of the leak, but the fire does not otherwise spread and just burned until the tank was empty. Contrast with some informal experiments some people I knew a long time ago did in their spare time; it was impossible to ignite smaller amounts of hydrogen in open air because it dispersed so quickly, but when a small amount was released into a closed, air-filled garbage can and ignited with a piezoelectric igniter, it blew the lid something like 30 feet into the air and melted the can.

Having spent a good chunk of my professional career working with fuel cells, I was always far more worried about the pressure in a hydrogen tank than the hydrogen itself. 2000psi cylinders are scary enough--they will become a missile if the regulator breaks--so the >10,000psi tanks in modern FCVs are that much worse. Carbon fiber is a strong material, though. The fuel cell itself only operates, I assume, at a few psi, so the only pressure danger is in the tank itself and the fueling hose and nozzle while fueling.

Pushmi-Pullyu said:
So, is this an excess of caution on Honda's part? Or Honda's lawyers requiring a ridiculous level of safety to avoid any possible injury lawsuit? Or is high-pressure storage of hydrogen more dangerous than I realize?
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If we're talking about the venting rig, it's just reasonable caution. Do it outside, of course, cordon off the area so some moron with a cigarette doesn't walk past it, and don't do it near a tall building or ventilation intake, since the plume could find its way inside or get sucked in as it rises and form an explosive mixture. I've seen very similar hydrogen venting schemes myself for amounts much smaller than what's stored in the tanks of a FCV.

Pushmi-Pullyu said:
...there is a leak in a H2 fuel tank which somehow catches fire and becomes a burning jet, it can't be seen with the human eye. The way NASA scientists and techs deal with the hazard, so I've read, is to walk around the tank holding a piece of cardboard in front of them. If they see an area of the cardboard char or catch fire, then they know they've found the leak.
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We always kept a straw broom handy for this--if you think there might be a fire, hold it in front of you to see if the bristles catch fire. We also, of course, used fancy optical flame detectors for the H2 fueling station we built.

My uncle, who worked in aerospace for many years, told me that the test facility for a hydrogen-based rocket program (Apollo, I think) he was peripherally involved in had thermal sensing wire running along the top of all hydrogen plumbing so that it would detect the burning plume if a leak and fire happened anywhere along it.
 
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M.M. said:
You're a bit off on the 25% LEL limit of Hydrogen there--it is potentially explosive in air in any mix between around 4% and 75%. It's one of the widest ranges of any gas, which is one of the reasons it warrants caution if there is a leak in an enclosed area.
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Hey, thanks for your comments M.M.

Well let's see: What I said upstream was:

Hydrogen is (as most of us know, from high school chemistry class) dangerous if it's mixed with oxygen; when the oxygen level reaches ~25%, it becomes explosive.
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That was rather careless of me; I meant a ratio of approx. 25% air to H2, not oxygen to H2.

Anyway, your comment reads like you know more about it than I do. That wouldn't be hard, since chemistry has never been my strong suit.

My comment was based on one of those "Mr. Science" videos, involving a Pringles can filled with H2. I've posted a similar one one below, but in this one, that "Mr. Science" claims a 2-to-1 ratio of hydrogen to air is needed before an explosion can occur. So that would mean ~33% air needs to be in the mix. That certainly does suggest the ratio can vary somewhat, if one Mr. Science claims 25% and another claims 33% air is needed.



M.M. said:
If a plume from a leak does catch on fire you just get a jet of flame. The only risk is if you build up a cloud in an enclosed space.
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Right. It irritates me that some people -- even people who practice critical thinking and ought to know better -- claim if the tank is punctured, all the hydrogen inside may instantly explode in a fiery inferno. Nope! There's no oxygen inside that tank to react with the hydrogen, so -- as you say -- what you'd get at worst would be a jet of flame, unless the entire tank ruptured.

M.M. said:
We always kept a straw broom handy for this--if you think there might be a fire, hold it in front of you to see if the bristles catch fire.
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And then, like the Wicked Witch of the West, you can use it to threaten the Scarecrow?
;)
 
Pushmi-Pullyu said:
I meant a ratio of approx. 25% air to H2, not oxygen to H2.
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I'm talking about H2 in air as well--the generally published LEL and UEL values are around 4% and 75%. Here's a paper that lists four different industrial standards of H2 in air (not pure O2) at atmospheric pressure on page 3:

http://conference.ing.unipi.it/ichs2005/Papers/120001.pdf

LEL values range from 3.6% to 4.2%. Those are of course worst-case industrial standards and not necessarily indicative of real-world performance.

But (I made a mistake on this before), those actually may be flammability limits (LFL). The explosive limit (the point at which the flame front travels faster than the speed of sound) is around 17% according to this site, which is closer to the 25% you mentioned, and may be where the value you were using came from. The discrepancy may come from differing definitions of LEL vs LFL, or industrial standards being more paranoid about explosive potential

As for that video, it's fun, but while I am neither a chemist nor a science teacher, based on a lot of safety trainings I've attended and the venting systems I've been involved with I don't think the "2:1 ratio" he keeps specifying is accurate in any scientific sense (he's also talking about the maximum at which it will explode, which is an UEL of 56% or UFL of 75%). I'm pretty sure that by the time the can in that video goes "boom" there's way less than a 2:1 mixture in it. The incoming hydrogen is already at lower than 100% due to the water vapor mixed in, and when he disconnects the tube at the bottom I doubt there is 100% mixing going on due to turbulence as the heavy, cool air is sucked in from the bottom to replace the hot, warm H2, so you have a partially-mixed front of air with a very low H2 concentration working its way up the can until a part that has at least 25% air reaches the top, causes the flame to propagate down into the low-fraction portion, and go boom.

The flame sitting on top of the can does do a great job of illustrating how light hydrogen is, happily shooting straight up from a hole even at atmospheric pressure.

I will, however, try to grab one of the professional chemists at work to verify what I'm saying here.
 
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Pushmi-Pullyu said:
Thanks for pointing that out. Clearly you've had some experience in the chemistry lab, far moreso than I have.
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Actually, the only time I ever spent in a chemistry lab was two semesters in college. However, do have some professional experience with hydrogen specifically--I was involved in building a hydrogen fueling station (back in Schwarzenegger's "Hydrogen Highway" days), and others where I work did first-responder training for early hydrogen stations (mostly for busses) across California.

I checked with our H2 safety expert, and he pointed me to a hefty printout of a NASA study we had on the shelf. Lots of curves based on danger limits in clouds of varying sizes and varying types of confinement. Long story short, LFL is 4% to 76% in air, and while most industrial sources use the term "LEL" when they really are talking about "LFL" to be paranoid,real-world LEL varies significantly depending on the situation--a small uncontained cloud requires a richer mixture to explode than a large uncontained cloud, and a contained mix will explode at an even lower fraction. But, ballpark, you're looking at around 25-30% to explode in an open cloud and down toward 15% if it's in a container.

Which pretty much confirms why they clear the area around the vent stack so thoroughly--it is possible to not just deflagrate (which can be pretty violent with hydrogen), but actually detonate (and the energy of ignition is ridiculously low, so even a slight static spark can set off an explosion). According to NASA a kg of H2 (which the Clarity holds more than), if ignited, can cause 3rd degree burns in a radius of over 10 feet away from the cloud itself.

None of which is to say that hydrogen is any more dangerous than the gasoline people have been driving around with for decades--that stuff is every bit as dangerous and potentially explosive, as the recent accident in Mexico demonstrated. Just that if you're venting several kilograms of it, you probably want to stand way back, just in case.

Random aside: We had a hydrogen electrolyzer that, under certain circumstances, would have hydrogen migrate through the membrane into the oxygen side. Someone termed this "uncontrolled recombination events", which is a very fancy way of saying "small explosions". It sounded kind of like little pinging sounds.
 
As mentioned in my previous post, I was called by Honda to have an appointment with dealer to "replace fuel cell stack". I sent in the car. I was told it will take about 1 week for this job. They provided a loaner car for me.
The work items on the paper:
- W: Perform campaign 18-148:6FC00 - 2017-18 Clarity FC fuel Cell voltage misdetection safety Recall
- C 19 Engine: Customer states stack replacement
- W: Perform campaign 19-006:6CJ00 - 2017-18 Clarity FC stack replacement PUD
- I 29 multipoint INSP
- I 29 set tire pressure

Dealer told me that the reason for FC stack replacement is that there is vapor developed in the FC stack and somehow generated HCI acid there. The acid will erode other parts of the engine.
 
AllenHuo said:
As mentioned in my previous post, I was called by Honda to have an appointment with dealer to "replace fuel cell stack". I sent in the car. I was told it will take about 1 week for this job. They provided a loaner car for me.
The work items on the paper:
- W: Perform campaign 18-148:6FC00 - 2017-18 Clarity FC fuel Cell voltage misdetection safety Recall
- C 19 Engine: Customer states stack replacement
- W: Perform campaign 19-006:6CJ00 - 2017-18 Clarity FC stack replacement PUD
- I 29 multipoint INSP
- I 29 set tire pressure

Dealer told me that the reason for FC stack replacement is that there is vapor developed in the FC stack and somehow generated HCI acid there. The acid will erode other parts of the engine.
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Continue above story.
Picked up my car today. Total 4 working days. All stated work in above post was done.
More description (and correction) on the paper about the campaign 19-006:6CJ00-2017-18 Clarity FC stack replacement PUD: Water improperly discharged inside the fuel cell stack mixes with hydrogen and oxygen, generating hydrogen peroxide. The hydrogen peroxide/water combination concentrates in one area, accelerating the deterioration of the electrolyte membrane in the fuel cell.
There is long list of parts/labor involved. But the main part is 3A100-5WM-A30 Kit FC Unit Assy.
 
AllenHuo said:
Water improperly discharged inside the fuel cell stack mixes with hydrogen and oxygen, generating hydrogen peroxide. The hydrogen peroxide/water combination concentrates in one area, accelerating the deterioration of the electrolyte membrane in the fuel cell.
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As someone who used to spend a lot of time designing fuel cell control systems, this is incredibly interesting to me (and I'm surprised Honda is saying it publicly). Every stack I've ever worked with has active humidification to prevent the membranes from drying out, and while getting evolved water out so it doesn't block flow paths was always a challenge I don't remember ever hearing about it being converted into hydrogen peroxide, or that as a cause of membrane deterioration. I'm going to have to talk to some of the stack designers and see what they have to say.

I am curious as to why the stack would have both hydrogen and oxygen on the same side of the membrane, though. Normally it's a never-the-twain-shall-meet situation, lest you get recombination, spot heating, water evolution in the wrong places, and a potential fire.
 
AllenHuo said:
As mentioned in my previous post, I was called by Honda to have an appointment with dealer to "replace fuel cell stack". I sent in the car. I was told it will take about 1 week for this job. They provided a loaner car for me.
The work items on the paper:
- W: Perform campaign 18-148:6FC00 - 2017-18 Clarity FC fuel Cell voltage misdetection safety Recall
- C 19 Engine: Customer states stack replacement
- W: Perform campaign 19-006:6CJ00 - 2017-18 Clarity FC stack replacement PUD
- I 29 multipoint INSP
- I 29 set tire pressure

Dealer told me that the reason for FC stack replacement is that there is vapor developed in the FC stack and somehow generated HCI acid there. The acid will erode other parts of the engine.
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Lot of people are getting the recalls done but not stack replacements.
I hear it is taking half a day.
The appointments are within 1-2 days of calling for service. Imagine that.
 
I've my Clarity FCX for a year now. It has about 15K miles. I did take in my car for addressing the recalls. I've noticed a significant drop in the range. The car averages about 50-55 miles/kg. I do see improvement in mileage when I use cruise control and drive at about 65-70mph. Based on the car average I expect it to give me a range of 275-285 miles upon refueling. But lately the range is only about 225-235 miles when the tank is full. Has anyone noticed similar issues?
I'm wondering if the hydrogen leak sensor is malfunctioning or may be it is winter weather related.
Further, the recall was related to hydrogen sensor malfuntion, I believe.
 
I have my Clarity FuelCell since Last May, and recently my range after a fill up is about 240miles...I had thought fuel cell car's range doesn't diminish during winter months...and to have 120 miles less than rated range kind of sucks...I am in NorCal...My co-worker's Mirai still shows about 280-290 after a fill up (we fill up at the same location). Also averaging 55miles / kg...I keep on thinking that maybe some liquid hydrogen got so "ICE'd" that the tank capacity somehow reduced...
 
Hi Folks,

I am on the waitlist for a 2019 Clarity Fuel Cell. Pls share your experiences on GAP Insurance and Excess Wear and Tear Insurance.

1. In your opinion is it even required? And if yes, how much did you pay for it?
2. Did you get it through the dealer or private insurance carrier? I currently have Geico and they don't offer it.
3. Is it advisable to get it before you drive the car off the lot or can you delay it?
 
While I have absolutely no experience with driving a FCEV, and have no desire at all to ever drive one, I have to wonder why anyone would spring for "Excess Wear and Tear Insurance" on a car which will be leased for 3 years or less. Surely you don't plan on keeping the car past the expiration of getting free fuel? Very, very few people are gonna pay $15-16 per kg for fuel for their car!
​
 
Picked up mine on September 1st, after waiting for a little over 5 months. We had a little scare here with some hydrogen shortage in the fall after the explosion of the facility down in Southern Cal as well as transport trucks. During that time, I've been getting my fill up in Mt. View at $18.7x/kg. I've recently tried filling up at various TrueZero stations from around the South Bay at $16.7x/kg. I had a little scare this past weekend as just about every station was empty, or got emptied out before I got there. I ended up getting refilled at the Shell Station in San Francisco with 11 miles left on my estimated range..

I've noticed that my range went from 300+ down to around 240-270 after each fill out about 2-3 weeks ago. I was getting around 66-70 miles/kg prior. But during the past 2-3 weeks, it was more like 60 miles/kg. I was trying to figure out what the cause may be: purity of the hydrogen? lower pressure during fill up? cold temperature outside? hydrogen from different manufacturer? liquid-converted vs gas hydrogen? So far, none of these seems to be the case. I was browsing through hoping to see if others have experienced the same thing. I just refilled this evening at the TrueZero by SFO, and the dashboard is showing that I have a range of 310 miles, and my trip back to Sunnyvale indicated I was getting 69.3 miles/kg.
 
Wow! I had no idea H2 was that expensive. That’s ~10 x more than my EV at current 3.93 miles/kWh with $0.10/kWhr and ~5x more than my HV at 50 mpg with gas at $2.50/gal.

With prices that high and availability that spotty , I don't think H2 is ready for prime time until the production/infrastructure matures.
 
Technically the fuel is free. Honda is paying for the fuel for the 3-year lease with $15k. At current rate, my calculation indicates that $5k would cover about 18.5k miles per year.

Let’s assume the price of H2 will remain the same, and you really want to take advantage of that 20k miles/year allowance, you’ll shell out $450 out-of-pocket to cover that last 1,500 miles. So you would really only be paying less than $40 of your own money per month for fuel...

But for most people, I think 18.5k miles should adequately cover your typical commutes.


Sent from my iPhone using Inside EVs
 
I think it's typical for the range to drop in cold weather. It's a combination of outside temp stressing the system coupled with more heater usage + pressure changes during fillup. Mine has gone down from 340ish to 280 or so. You should join he fb group on honda clarity fc. Members are very helpful and responsive.
 
gundam91 said:
Technically the fuel is free. Honda is paying for the fuel for the 3-year lease with $15k. At current rate, my calculation indicates that $5k would cover about 18.5k miles per year.

Let’s assume the price of H2 will remain the same, and you really want to take advantage of that 20k miles/year allowance, you’ll shell out $450 out-of-pocket to cover that last 1,500 miles. So you would really only be paying less than $40 of your own money per month for fuel...

But for most people, I think 18.5k miles should adequately cover your typical commutes.


Sent from my iPhone using Inside EVs
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Yes, it’s a giveaway covered in the lease but is in no way financially viable for Honda. At some point, people are going to have to pay for the fuel themselves if this is ever going to go mainstream.
 
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