Hydrogen and FCEVs discussion thread

[DaveEV]

I suspect the PHEVs will continue to use the amazingly reliable NiMh chemistry for their ~1 kWh battery.

I'm not aware of any current PHEVs that use NiMH and the only manufacturer still using NiMH for their hybrids is Toyota, everyone else has moved on to Lithium. I suspect that even Toyota will move to Lithium in their next gen Prius.

 

[abasile]

What I still haven't seen answered is whether or not a fuel cell loses power due to altitude effects, or whether there's enough excess O2 at altitude to keep the reaction providing full power. AFAIK there's no compression taking place, just a straight intake of air at atmospheric pressure.

Good question. I'd like to see a FCEV take on Pike's Peak!

Another concern I have is braking on mountain descents. The ~1 kWh battery is far too small to offer adequate regenerative braking on the 4900' descent we do regularly; our Prius battery fills after the first several hundred feet of descending. At the same time, a FCEV has no engine to use for braking as in a PHEV or HEV. Relying solely on friction braking is not recommended due to overheating. All of that "excess" potential energy needs to get dumped somewhere. Maybe a larger battery is needed, in which case they might as well add a plug.

 

[RegGuheert]

Good question. I'd like to see a FCEV take on Pike's Peak!

Another concern I have is braking on mountain descents. The ~1 kWh battery is far too small to offer adequate regenerative braking on the 4900' descent we do regularly; our Prius battery fills after the first several hundred feet of descending. At the same time, a FCEV has no engine to use for braking as in a PHEV or HEV. Relying solely on friction braking is not recommended due to overheating. All of that "excess" potential energy needs to get dumped somewhere. Maybe a larger battery is needed, in which case they might as well add a plug.

It seems as if an electrolyzer might be in order. Are any fuel cells reversible? Put water in the output and get hydrogen and oxygen back?

Another solution would be a plug-in FCEV with a Volt-sized battery.

 

[walterbays]

Good question. I'd like to see a FCEV take on Pike's Peak!

Each type of vehicle can be suitable for many environments without being suitable for all. A BEV isn't suitable for someone with a long daily commute and no workplace charging. You don't need to put greately excess batteries in all BEV's in order for them to still be suitable for a large number of people. An ICE isn't very suitable for someone who lives in a city where they like to breathe the air, or in a nation subject to attacks by oil funded terrorists, or on a planet subject to catastrophic climate change. But still for quite a few years it will remain the most suitable choice for a lot of people.

So if a FCEV isn't suitable for Pikes Peak that's no real problem. If it's not suitable to be sold in mountain states like Colorado it can still be wildly successful in most of the country. If it's not suitable to be sold in the hills of Southern California then the makers might want to do a cost benefit analysis of adding a larger battery, and if it needs to be very large, of adding a plug.

The question remains whether it's a good idea to spend scarce public money on greatly more expensive FCEV infrastructure to support more expensive FCEV vehicles with questionable environmental benefits, in lieu of putting the money into proven technology. Or whether only a modest public investment in FCEV is being made, in line with what was done with BEV and PHEV at a similar stage in their development, on the chance that FCEV may finally turn out to be a viable solution for many people.

 

[AndyH]

I suspect the PHEVs will continue to use the amazingly reliable NiMh chemistry for their ~1 kWh battery.

I'm not aware of any current PHEVs that use NiMH and the only manufacturer still using NiMH for their hybrids is Toyota, everyone else has moved on to Lithium. I suspect that even Toyota will move to Lithium in their next gen Prius.

I agree on the PHEVs. That was a typo - supposed to have been 'FCEV', but that's incorrect as well - Hyundai's updated web page says they're using 'Li-Polymer' as well.
https://www.hyundaiusa.com/tucsonfuelcell/

I'm not sure LiPo is a better choice than NiMh in vehicles like the Tucson. The battery is performing the same functions in the Tucson FCEV as is the battery in the Prius and NiMh is a proven tech with a very long service life.

 

[RegGuheert]

I'm not sure LiPo is a better choice than NiMh in vehicles like the Tucson. The battery is performing the same functions in the Tucson FCEV as is the battery in the Prius and NiMh is a proven tech with a very long service life.

Toyota has achieved long life from NiMh, but not Honda. And Toyota now has all the market share. Both used top-quality cells, so I'll assume it depends on the design of the battery. I don't think Honda achieved isothermal conditions in their design.

 

[abasile]

So if a FCEV isn't suitable for Pikes Peak that's no real problem. If it's not suitable to be sold in mountain states like Colorado it can still be wildly successful in most of the country. If it's not suitable to be sold in the hills of Southern California then the makers might want to do a cost benefit analysis of adding a larger battery, and if it needs to be very large, of adding a plug.

I agree that mountain capabilities are not important for a great many people in less rugged areas of the country. However, for any vehicle with long range to be sold for general, personal/consumer use in Western states including California, I think it needs to be capable of handling mountains. It seems that virtually every educated person of any means in California wants to at least occasionally drive to Yosemite, Big Bear, Mammoth, Lake Tahoe, Julian, etc. Up here near Big Bear, we now see Teslas fairly regularly, and we are no longer the only LEAF-owning mountain residents.

The question remains whether it's a good idea to spend scarce public money on greatly more expensive FCEV infrastructure to support more expensive FCEV vehicles with questionable environmental benefits, in lieu of putting the money into proven technology. Or whether only a modest public investment in FCEV is being made, in line with what was done with BEV and PHEV at a similar stage in their development, on the chance that FCEV may finally turn out to be a viable solution for many people.

I'm fine with some public support for FCEVs. At least for now, though, I think BEVs should continue to get priority in terms of CARB credits and funding.

 

[evnow]

I'm fine with some public support for FCEVs. At least for now, though, I think BEVs should continue to get priority in terms of CARB credits and funding.

The problem with FCEV is that the infrastructure is bloody expensive. One fueling station will eat up the funds for a dozen QC.

 

[smkettner]

I'm fine with some public support for FCEVs. At least for now, though, I think BEVs should continue to get priority in terms of CARB credits and funding.

The problem with FCEV is that the infrastructure is bloody expensive. One fueling station will eat up the funds for a dozen QC.

So the FCEV needs 600 mile range to compete on infrastructure. Assuming 12 QC would get LEAF 600 miles.
In a grid structure you may not get LEAF 250 miles in 4 to 6 directions.
With twice the range LEAF EV would seem to win hands down.
The real burden with FCEV is they need the infrastructure for all use where EV only needs enough to cover long distances.

 

[GRA]

So if a FCEV isn't suitable for Pikes Peak that's no real problem. If it's not suitable to be sold in mountain states like Colorado it can still be wildly successful in most of the country. If it's not suitable to be sold in the hills of Southern California then the makers might want to do a cost benefit analysis of adding a larger battery, and if it needs to be very large, of adding a plug.

I agree that mountain capabilities are not important for a great many people in less rugged areas of the country. However, for any vehicle with long range to be sold for general, personal/consumer use in Western states including California, I think it needs to be capable of handling mountains. It seems that virtually every educated person of any means in California wants to at least occasionally drive to Yosemite, Big Bear, Mammoth, Lake Tahoe, Julian, etc. Up here near Big Bear, we now see Teslas fairly regularly, and we are no longer the only LEAF-owning mountain residents. <snip rest>

Agreed on the need for adequate regen storage in Ca. That's one of the reasons we need to take one up to the mountains and back. I suspect it's a cost/weight/space issue at the moment. The FCHV Tucson is considerably heavier than the gas version, and bigger batteries would make it heavier still (although it'd still be a lot lighter than a BEV of equivalent range]. Perhaps this will need to wait for further improvement of fuel cell power density and/or battery energy density/specific energy, but until somebody tries it we won't know. Hyundai is apparently planning to introduce their next gen fuel cell around 2016, so if a bigger battery is needed maybe that's when it will happen.

The other possibility is that they just piss the power away once the battery's full - you could divert it into a resistor or something, just like the way off-grid wind and water turbines are regulated when the battery/water tank is full. Definitely questions to ask.

 

[AndyH]

So if a FCEV isn't suitable for Pikes Peak that's no real problem. If it's not suitable to be sold in mountain states like Colorado it can still be wildly successful in most of the country. If it's not suitable to be sold in the hills of Southern California then the makers might want to do a cost benefit analysis of adding a larger battery, and if it needs to be very large, of adding a plug.

I agree that mountain capabilities are not important for a great many people in less rugged areas of the country. However, for any vehicle with long range to be sold for general, personal/consumer use in Western states including California, I think it needs to be capable of handling mountains. It seems that virtually every educated person of any means in California wants to at least occasionally drive to Yosemite, Big Bear, Mammoth, Lake Tahoe, Julian, etc. Up here near Big Bear, we now see Teslas fairly regularly, and we are no longer the only LEAF-owning mountain residents.

The question remains whether it's a good idea to spend scarce public money on greatly more expensive FCEV infrastructure to support more expensive FCEV vehicles with questionable environmental benefits, in lieu of putting the money into proven technology. Or whether only a modest public investment in FCEV is being made, in line with what was done with BEV and PHEV at a similar stage in their development, on the chance that FCEV may finally turn out to be a viable solution for many people.

I'm fine with some public support for FCEVs. At least for now, though, I think BEVs should continue to get priority in terms of CARB credits and funding.

High altitudes don't appear to be a problem. I doubt Ford was the only company driving mountains during their FCEV testing, and we have an example early in the thread of a complete fuel cell system for powering an electric unmanned aerial vehicle. I recall one of Robert Llewellyn's shows let us hear one of the fans used to push air into the fuel cell stack.

http://corporate.ford.com/microsite...11-12/environment-products-plan-migration-fcv

From 2005 to 2009, Ford participated in a technology demonstration program partially funded by the U.S. Department of Energy (DOE), as well as other government supported demonstration programs in Canada and Europe. A total of 30 Ford Focus FCVs were in operation in these programs. These vehicles were tested to demonstrate technical feasibility, performance durability and reliability; for example, they were subjected to driving tests at sub-zero temperatures and high altitudes to prove vehicle performance under a range of customer-encountered driving environments. By 2009, these vehicles had accumulated more than a million driving miles without significant technical problems, thereby demonstrating the reliability of fuel cell powertrain systems in real-world driving conditions.

http://www.motortrend.com/auto_shows/1311_hyundai_tucson_fuel_cell_vehicle_debuts_in_los_angeles/

The system has been tested at temperatures ranging from -4F to greater than 117F, at humidity levels as low as 0-20 percent (also hard on a fuel cell), and at altitudes higher than 8500 feet. It has also survived all standard crash tests plus an 8-g sled test without going all Hindenburg.j

[youtube]http://www.youtube.com/watch?v=hYYR_wG-x_E[/youtube]
(What a difference four years makes, eh?)

 

[GRA]

<snip>

High altitudes don't appear to be a problem. I doubt Ford was the only company driving mountains during their FCEV testing, and we have an example early in the thread of a complete fuel cell system for powering an electric unmanned aerial vehicle. I recall one of Robert Llewellyn's shows let us hear one of the fans used to push air into the fuel cell stack.

http://corporate.ford.com/microsite...11-12/environment-products-plan-migration-fcv

From 2005 to 2009, Ford participated in a technology demonstration program partially funded by the U.S. Department of Energy (DOE), as well as other government supported demonstration programs in Canada and Europe. A total of 30 Ford Focus FCVs were in operation in these programs. These vehicles were tested to demonstrate technical feasibility, performance durability and reliability; for example, they were subjected to driving tests at sub-zero temperatures and high altitudes to prove vehicle performance under a range of customer-encountered driving environments. By 2009, these vehicles had accumulated more than a million driving miles without significant technical problems, thereby demonstrating the reliability of fuel cell powertrain systems in real-world driving conditions.

http://www.motortrend.com/auto_shows/1311_hyundai_tucson_fuel_cell_vehicle_debuts_in_los_angeles/

The system has been tested at temperatures ranging from -4F to greater than 117F, at humidity levels as low as 0-20 percent (also hard on a fuel cell), and at altitudes higher than 8500 feet. It has also survived all standard crash tests plus an 8-g sled test without going all Hindenburg.j

Andy, maybe this was addressed in the video (the closed captioning is unintentionally hilarious, if not terribly coherent), but 'tested higher than 8,500 feet' isn't the same thing as 'not a problem'. 'Pushing' air into the stack doesn't necessarily mean compressing it. I 'tested' my dad's '76 Peugeot 504 diesel at altitudes over 10,000 feet MSL, with density altitudes up to 14,000 feet. Yes, it could get to those altitudes, but it was definitely ill-suited for them. The car had a curb weight of 3,000 lb. but only 65 hp @ SL, and took forever to rev up. It took about 3 miles of straight, level road to safely pass someone on a two lane road at or above 4,000 feet density altitude, its top speed was inadequate, and it overheated during the 13 mile/3,160 foot climb up from Lee Vining to Tioga Pass in Yosemite with two of us and gear on a typical summer day, when we got stuck behind an RV and had to crawl along at a speed too low to provide sufficient airflow to the radiator, nor had we a hope of passing. We had to pull off halfway up and kill two hours waiting for the car to cool down.

The Tucson starts with about a 50% higher power/weight ratio @ SL (4,100/134 = 30.6 lb./hp vs. 3,000/65= 46.2 lb./hp) than the 504 had, and will do 0-60 in 12.9 seconds versus the Peugeot's 28.1 seconds. so it starts out way ahead - IIRR my '88 Subaru Turbo only did 0-60 in 13.4 or maybe it was 13.7 seconds, although it seemed to have the same power at 12,000 feet as it did at sea level, and could pass fairly easily on mountain roads even while loaded. 0-60 in 13+ seconds seems slow today, but I don't recall ever having any trouble merging into traffic, so 12.9 seconds doesn't bother me. But after far too many white-knuckled merges in the 504 :shock: , every car seemed easy.

Do you know of any site that has performance specs at altitude, or an engineer describing fuel cell output at some height above sea level, and/or what's going on?

Edit: Aha, here's something:

"Performance of Proton Exchange Membrane Fuel Cell at High-Altitude Conditions"

http://arc.aiaa.org/doi/abs/10.2514/1.20535?journalCode=jpp" onclick="window.open(this.href);return false;

So, taking the number mentioned in the paper of -1.5%/1kft above 1kft. for unpressurized fuel cells as representative (lacking anything better to go on), at a density altitude of 10kft (not uncommon going over Donner summit up to Tahoe in summer) we'd be down 14.5% on power. That's considerably better than an unpressurized ICE, but nowadays turbos are all the rage and it would depend what their critical altitude is.

Edit: Here's another one, with graphs which seem to show similar performance degradation as above:

http://www.nfcrc.uci.edu/3/activities/researchsummaries/Hybrid_FC-GT_Systems/Proton_exchange_Membrane_Fuel_Cell/HYBRIDfuelCELL_PEMFC.pdf" onclick="window.open(this.href);return false;

And one more, which talks about air compressor power requirements increasing fuel consumption 10-19% as altitudes increase up to 3km:

http://www.diva-portal.org/smash/get/diva2:7360/FULLTEXT01.pdf" onclick="window.open(this.href);return false;

 

[abasile]

I do find it interesting to learn of the operational tradeoffs involved with FCEVs. It's good to know that loss of power with altitude probably isn't all that bad. As for regen braking, we might have to wait for folks like Mr. Bush to try a good mountain drive.

http://www.motortrend.com/auto_shows/1311_hyundai_tucson_fuel_cell_vehicle_debuts_in_los_angeles/

The system has been tested at temperatures ranging from -4F to greater than 117F, at humidity levels as low as 0-20 percent (also hard on a fuel cell), and at altitudes higher than 8500 feet. It has also survived all standard crash tests plus an 8-g sled test without going all Hindenburg.j

I didn't realize that low humidity levels are hard on fuel cells. Do you know how/why this is so? During our seasonal "Santa Ana" wind events, it's not at all unusual for the relative humidity to drop into the single digits.

 

[GRA]

http://www.motortrend.com/auto_shows/1311_hyundai_tucson_fuel_cell_vehicle_debuts_in_los_angeles/

The system has been tested at temperatures ranging from -4F to greater than 117F, at humidity levels as low as 0-20 percent (also hard on a fuel cell), and at altitudes higher than 8500 feet. It has also survived all standard crash tests plus an 8-g sled test without going all Hindenburg.j

I didn't realize that low humidity levels are hard on fuel cells. Do you know how/why this is so? During our seasonal "Santa Ana" wind events, it's not at all unusual for the relative humidity to drop into the single digits.

From the last paper I linked, a doctoral dissertation by Kristina Haraldsson, dating from 2005:

"2.3.1 Water Management

"A water management system is needed to humidify the reactants for fuel cells operating
temperature above 60 °C [Larminie & Dicks, 2000]. To ensure adequate conductivity and
long life of the membrane, water must be supplied in sufficient amounts and distributed in
a homogeneous way. There must be a balance though to avoid the flooding, or water
blocking the pores of the electrodes.

"A water balance, i.e. the amount of condensed water equals the amount of water needed
for humidification, is an important feature in automotive applications. In order for the fuel
cell system to be water self-sustaining, therefore, the water management system also
contains equipment to condense the exhaust flows and collect and re-use the water.
The way the humidification is performed varies, ranging from external humidification,
e.g. direct water injection and enthalpy wheels, internal humidification such as using wicks
or self humidification, to no humidification at all. Removing or minimizing the external
humidification would simplify the fuel cell system in terms of space and heat supply.
However, the control of the internal humidification has proven to be difficult [Eckl et al.,
2004] and the no humidification is reported by Rajalakshmi et al. (2004) to increase the fuel
cell system weight and consumer more power.

"2.3.2 Air Management

"The fuel cell stack is supplied with intake air by a blower or a compressor, depending on
the desired operating pressure. Pressurized systems allow for smaller and more compact
fuel cell stacks, although to the cost of the compressor power requirements. Also, the
efficiency is low at low speeds and the compressor may behave sluggishly, i.e. not
responding instantly to load changes. The operating pressure of a fuel cell stack is usually
between atmospheric pressure and 3 bar. The turbocompressor and the twin-screw
compressor are the most investigated options due to their low weight and small size. Kulp
et al. (2002) found that the turbocharger is more efficient than the twin- screw compressor,
especially at low mass flows. However, a neutral water balance was more difficult to
maintain with a turbocharger than in a twin-screw set-up."

 

[GRA]

What we want to know is addressed in the paper between pages 41-54. "Fuel Cell Vehicle Performance" starts on page 41; "Fuel Cell Hybrid Vehicle Performance", particularly relevant as one of the vehicles modeled was an SUV, starts on page 47. For instance, fuel efficiency decreases 19% on the US06 cycle at 3km (9,843 ft.).

 

[AndyH]

What we want to know is addressed in the paper between pages 41-54. "Fuel Cell Vehicle Performance" starts on page 41; "Fuel Cell Hybrid Vehicle Performance", particularly relevant as one of the vehicles modeled was an SUV, starts on page 47. For instance, fuel efficiency decreases 19% on the US06 cycle at 3km (9,843 ft.).

Note that pressurizing stacks allows an increase in power density, and that one of the most significant changes in fuel cell stacks since 2005 is the jump in power density. I would just about bet money that the push for commercialization after 2005 has provided us with FC stacks that are pressurized and for which the compressor losses and altitude performance are already included in the efficiency numbers.

http://www.hydrogen.energy.gov/pdfs/htac_may2012_hyundai.pdf
http://www.fch-ju.eu/sites/default/files/documents/ga2010/sae-hoon_kim.pdf



http://www.telegraph.co.uk/motoring/first-drives/8989897/Hyundai-ix35-fuel-cell-review.html

Hyundai’s experience with UTC has influenced the development of its own fuel-cell, which only requires air at low pressure to reduce noise and maximise overall efficiency, although the ix35’s blower does slightly pressurise the cell and purge it of water when switching off.

“We don’t use air compressor because energy consumption is very high,” says Kwon Tae Cho, a senior research engineer on the fuel cell project. “We use an air blower instead, which means net power goes up, but noise is low.”

 

[AndyH]

http://corporate.ford.com/microsite...11-12/environment-products-plan-migration-fcv

From 2005 to 2009, Ford participated in a technology demonstration program partially funded by the U.S. Department of Energy (DOE), as well as other government supported demonstration programs in Canada and Europe. A total of 30 Ford Focus FCVs were in operation in these programs. These vehicles were tested to demonstrate technical feasibility, performance durability and reliability; for example, they were subjected to driving tests at sub-zero temperatures and high altitudes to prove vehicle performance under a range of customer-encountered driving environments. By 2009, these vehicles had accumulated more than a million driving miles without significant technical problems, thereby demonstrating the reliability of fuel cell powertrain systems in real-world driving conditions.

Andy, maybe this was addressed in the video (the closed captioning is unintentionally hilarious, if not terribly coherent),

No, the only on-topic function of the video was to hear the sounds of the air blower. I don't expect the captions covered that very well at all. :lol:

... but 'tested higher than 8,500 feet' isn't the same thing as 'not a problem'. 'Pushing' air into the stack doesn't necessarily mean compressing it.

Ok, I realize this place is in hard-core left-brain mode but I selected the snip from Ford to provide the most concise summary of things FCEV developers apparently evaluate. I found a number of companies that perform fuel cell testing, and some of the required tests are conducted in a chamber with reduced atmospheric pressure to simulate high-altitude operation. The vehicle manufacturer takes the cars on the road to 'prove vehicle performance' fits with the lab work. Ummm...as to "tested" not necessarily equaling "not a problem"...the function of a vehicle is to move people from point A to point B. If the vehicle was unable to move people up a hill that would in fact be "a problem" in my world.

As for fans, blowers, and compressors - I agree that 'pushing' air isn't necessarily 'compressing' it (though recall that stuffing a higher volume of a fluid into a smaller space tends to change things). In the aircraft world, for example, there are different ways to operate a turbo-charger. In one mode of operation, the device is used to force more air into the engine with the goal of increasing the power available (a 100 hp non-turbo engine might become a 150 hp engine when blown). In another mode, the device is not used at sea level (or used very little) yet is made to pump more air at higher altitudes (to maintain atmospheric pressure in the engine). This allows an engine that is rated to produce 160 hp at sea level continue to produce about that amount of power at altitude. This is turbo-normalizing. I'll bet Hyundai's using the fan to provide a bit of both functions.

Turbocharging VS. Turbonormalizing
http://www.nar-associates.com/technical-flying/turbo/turbonormalization_wide_screen.pdf

edit... Guy - It looks like your links covered this well enough. I'd like to see results of actual tests for a complete fuel cell system as fielded. So far I'm not finding much. Electric turbochargers are in use today as well and they cure 'turbo lag' - should bode well for maintaining pressure in the fuel cell stack. I hope there aren't any 'gotchas' in this tech similar to the Leaf's hot climate challenges.

 

[jsongster]

90 pages and counting... Come on... let's go for 100!

http://www.greencarreports.com/news...s-have-been-called-hydrogen-batteries-instead

A BEV by any other name... so an FCEV is just a BEV whose battery is fluid refillable.

Hydrogen is just another recharge method... for a battery. So what is all this fuss about... another battery with future promise.

 

[GRA]

<Snip prior>

... but 'tested higher than 8,500 feet' isn't the same thing as 'not a problem'. 'Pushing' air into the stack doesn't necessarily mean compressing it.

Ok, I realize this place is in hard-core left-brain mode but I selected the snip from Ford to provide the most concise summary of things FCEV developers apparently evaluate. I found a number of companies that perform fuel cell testing, and some of the required tests are conducted in a chamber with reduced atmospheric pressure to simulate high-altitude operation. The vehicle manufacturer takes the cars on the road to 'prove vehicle performance' fits with the lab work.

Pity Ford and Hyundai didn't do that with their HEVs and PHEVs before posting dynamometer test-only mpg ratings. . . but I digress.

Ummm...as to "tested" not necessarily equaling "not a problem"...the function of a vehicle is to move people from point A to point B. If the vehicle was unable to move people up a hill that would in fact be "a problem" in my world.

It all depends on what conditions the customer considers acceptable, doesn't it? It was entirely possible to drive that 504 up from Lee Vining over Tioga Pass in some conditions (at night or in fall, no other traffic so could pick my speed, just myself and gear in the car), but not others. Since I needed to be able to do so in the majority of the 'other' conditions it wasn't suitable for me, but might be for others. The question is how limiting the conditions are, for how many people. If you can cover 85% of the potential user population and conditions, you may be fine, 95% definitely. But 60% or less, probably not. Which is why I'm a big fan of empirical testing under field conditions, especially with new tech, instead of relying on the claims of company reps.

<snip areas of agreement>

 

[AndyH]

Ummm...as to "tested" not necessarily equaling "not a problem"...the function of a vehicle is to move people from point A to point B. If the vehicle was unable to move people up a hill that would in fact be "a problem" in my world.

It all depends on what conditions the customer considers acceptable, doesn't it? It was entirely possible to drive that 504 up from Lee Vining over Tioga Pass in some conditions (at night or in fall, no other traffic so could pick my speed, just myself and gear in the car), but not others. Since I needed to be able to do so in the majority of the 'other' conditions it wasn't suitable for me, but might be for others. The question is how limiting the conditions are, for how many people. If you can cover 85% of the potential user population and conditions, you may be fine, 95% definitely. But 60% or less, probably not. Which is why I'm a big fan of empirical testing under field conditions, especially with new tech, instead of relying on the claims of company reps.

I'm sure we all have car horror stories. I drove some old vehicles that could almost get out of their own way, or that weren't useful during hot days without the cooling system boiling over, as well - but it's not the 1960s any more.

Sure - it would be cool if equipment manufacturers posted every document they have on their website but I think we can both agree that's not going to happen. This is why I've talked about 'information warfare' and 'marketing VS. reality' in other parts of this forum - we 'little people' get marketing info. That's why we have to spend so much time and effort collecting flakes of paint from under the curtain and trying to paint an accurate picture with them. :lol:

But - and I think this is an important but - just because some 'want' data and cannot find it does not mean those data don't exist. The first place I'd start is with Federal vehicle design/safety rules for the 'minimum standards' and then work 'toward' a specific vehicle from there. I'd bet we'll find that the current minimum standards results in a vehicle that we don't have to push over a hill on an exceptionally hot summer day.