Economic Reasons to Buy an EV instead of a gas powered car

Discussion in 'Tech: Batteries, Charging, Alternative Energy' started by Mr_funnypuns, Nov 2, 2019.

  1. Mr_funnypuns

    Mr_funnypuns Active Member

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    Sometimes when discussing EVs we get passionate about them, and bring up the topic of climate change to justify the claim that anything that man can do to control climate change, we should be doing. Some of it may be worth doing, and I’ve done some of the things that are worth doing. 7.5 kW on my roof. DRiving a Prius for 17 years (my first was an ‘02 that got crunched in a crash). Walking and riding a bike when I can. Now looking seriously at EVs because they look mature enough to rely on. And more. However, I’m under no illusions... my personal choices are completely irrelevant to the climate: the degree to which it is changing is unaltered because I personally made these choices. So, I had to make them for other rational objective reasons.

    The economics of why an EV makes sense is actually a fascinating analysis that is vastly oversimplified. I’m a six sigma black belt, and so I’ve been trained to think about choices in terms of rational value.

    Here’s one point to consider: over the life of a gasoline car, how much time do you spend at the pump, and what value do you place on that time? It’s not an arbitrary number. People who pump gas rather than that change an EV are making a decision to fill a 25-gallon tank with gas at $3 a gallon. It takes ten minutes to fill that car up with $75 dollars of fuel. It takes maybe another 10 min to get in and out of the station. A driver might fill a gas tank up once a week for 60 years, so that works out to a total of 60 * 52 * 1/3 hour = 1040 hours. 1040 hours spent smelling gasoline, much in cold weather, rainy weather. Time that could be spent with a shorter commute, giving you extra sleeping time, an extra cup of coffee, an extra hug with family, or just allowing a lower stress level when driving.

    When we make decisions about EVs we often neglect the value of our own free time, because we’ve never bothered to place a dollar value on it. Think about this: if we work 50 hours a week, and we get maybe an hour a day free... then you could value that hour of free time at 50x your hourly pay. That’s a reasonable estimate. Suppose you are working even a minimum wage job at $11 an hour. That means the the value of the time you spend pumping gas each year is 52 * 1/2 hour per week * $11 per hour * 50 =$14,300!!!

    No way to convert that time to cash of course.... but it does serve to show that the time savings granted by an EV in terms of just the time saving at the pump is more significant a value than we think it is... and maybe should factor into our decision about whether to by an EV or not.

    I started this topic to encourage rational economic thought about why to buy an EV... to avoid the polemics of debating whether EVs help the environment. The impact of an EV to an individual’s life is quantifiable and measurable, and is of great interest to anyone who is rational.

    I wonder how many cost savings, time savings, quality of life improvements, or avoided irritations we can indentify, and having done that, what dollar value might be placed on them? Remember in this exercise, you can’t count the value to a group... only to the individual, because the choice to purchase an EV is an individual choice, not a group choice.
     
  2. Mr_funnypuns

    Mr_funnypuns Active Member

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    Some things that EV owners don’t need to deal with
    1) REplacement lead acid batteries (0 vs. 1 every 3-4 years)
    2) Frequent brake service (100k brake life vs. 40k)
    3) Alternator replacement (0 vs. once in 200k)
    4) Starter replacement (0 vs. once in 200k)
    5) oil service (0 vs. 4x a year/3000 miles)
    6) trans service (0 vs. once every 100k)
    7) Intakee air filter (0 vs. once a year)
    8) Spark plugs (once every 100k)
    9) Catalytic converter(s) (once every ???)
    10) accessory belts & radiator hoses (0 vs. every 50k?)
    11) RAdiator Leaks ( 0 vs. once every ???)
    12) Fuel pump failure (0 vs. once every ???)
    13 Fuel injector replacement (0 vs. once every 200k)
    14) RAdiator FAn Failures
    15) Transmission / differential / transfer case Failures
    16) Timing Belt Service
    17) Lifters/Rockers/Rings etc. wearing out at ~250k
    18) camshaft flattened lobes

    + avoided time at the shop
    + avoided time keeping shop service writers & mechanics honest

    Anyone else have additions to the list?
     
  3. DucRider

    DucRider Member

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    While a nice list, some things you need to update.

    1) EV's DO have a 12V lead acid battery and it does need to be replaced periodically
    5) Oil changes are now 1 yr/10K on most vehicles and/or heat pump systems
    6) Most EV's will have gear oil that needs changing periodically
    11) EV's have radiators for thermal management
    12) see #11
    15) EV's also have one or more differentials

    On the con side, EV's have a large and expensive battery pack with a finite life span (tbd). But for routine maintenance, there is no doubt the EV is vastly superior.

    For shows, we have a cutaway BMW ICE we display side-by-side with an AMR (now part of Borg Warner) electric motor. ~1,500 moving parts vs ~4. 7,500 mile service interval vs 1,000,000 (est). The AMR is >400 HP and weighs <100 lbs. The visual really seems to reinforce the simplicity in a way words cannot.
     
  4. Mr_funnypuns

    Mr_funnypuns Active Member

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    Thanks for the corrections. It surprised me that EV still lead acid batteries. But thinking about it you do need a low voltage source to boot the system. So tgat makes sense... and means that I could crank start this car with a hand generator in tfw event of a dead battery.

    coolant system makes sense now that I looked it up. There’s a write up here

    https://teslamotorsclub.com/tmc/threads/tesla-thermal-management-system-explanation.88055/


    on some details of Tesla’s thermal management. I’ll wait and see the technical details from Rivian

    differentials on some EV... I guess I was thinking of Rivian’s 4 motors and extending to an invalid generalization.

    will revise list in a few days. See if there are other additions or corrections.
     
  5. electruck

    electruck Active Member

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  6. Feathermerchant

    Feathermerchant Active Member

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    EVs have a radiator/condenser cooling fan. The system operates at a much lower temperature which may improve durability.
    Tesla EVs (as of now) require no fluid change to the gearbox. There is also a pump and filter which I guess makes that possible.
    Supposedly the Model 3 drive unit is designed and tested for 1M miles operation. That's a lot of miles.
    EVs have an inverter which they cannot live without.
    EVs have an onboard charger
    EVs have a DC-DC converter to make 12V from whatever battery voltage.

    Still an EV is my choice because performance, saving the planet and at least Tesla's have a very high safety rating and just keep getting more features (safety and others) thru the over-the-air updates.
     
  7. Mr_funnypuns

    Mr_funnypuns Active Member

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    Operating temperature is a key parameter in doing a reliability estimate. Take any measured failure rate, and it goes up a factor of six as the temperature rises from 25C to 50C. When applied to inverters,a critical part of the car, keeping the temperature of the solid state switches low is why the inverters of the leaf, Tesla, VW, BMW, and the venerable collection of hybrids do not experience inverter failures. There are relatively few electronic parts in such a device, and I’d expected the system to be engineered for a failure rate better than 3.5 failures per million hours, under the maximum operating temperature of the system. This would give an expected service life of 87,600 hours.

    If we drive 20000 miles a year at an average speed of 45 mph, this equates to 444 hours per year, which means the service life of the inverter might approach 50 years.

    The keys to inverter longevity are:
    1. Selecting the right voltage parts - voltage causes failures as fast as heat
    2. Liquid cooling - keep the temperature of the switches (IGBT, FET, THYRISTOR) down below 50C
    3. Select capacitors to handle the working current. Cheap aluminum electrolytic parts won’t endure
    4. Correctly design the control system using FMEA to anticipate and prevent catastrophic failure modes
    5. Manufacturing build quality. All the good design in the world does no good if there’s a bad solder joint
    6. Design qualification. Test it to failure. Know the actual MTBF meets or exceeds the design MTBF
    The track record of cars using inverters is very good... but I don’t have any data on the number of inveter failures in the past 20 years.Personally, mine have worked flawlessly for 17 years.I don’t think we assign a very high failure rate to the inverter, and therefore we can assign a low cost of operation.

    On a slightly different note, I’m going to add ignition wires, and coil packs. Unlike an inverter in a properly designed car, these are subject to heat, and do fail. Breakdown of insulation...
     
  8. electruck

    electruck Active Member

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    ICE engines have numerous sensors, solenoids, valves, etc that are the source of many problems: air flow/pressure sensors, crank and cam position sensors, variable valve/cam timing actuators, transmission speed sensors, O2 sensors.
    There are also a variety of gaskets prone to leaks: valve cover, head, oil pan, transmission pan, oil filter. Similar with gas caps and radiator fill caps.
    In addition to accessory belts and radiator hoses, there are many vacuum tubes and connections which get brittle with age and exposure to heat leading to leaks and incorrect air/fuel ratios.
    Fuel filter replacements.
    Various harmonic balancers such as the crankshaft pulleys and dual mass flywheels.
    Accessory drive pulleys.
    Many engines these days have reduced displacement and added forced induction. In the case of current Volvos, this includes both a supercharger and a turbocharger along with an intercooler an associated plumbing.
    While Rivian will still have the axle half shafts (motor to wheel) with CV joints, there will be no main drive shaft with its central CV joint or flex joint/disc/guibo at the transmission.
    I haven't seen details of how the electric motors are mounted but their NVH characteristics should not require the failure prone fluid filled mounts frequently used with ICEs. (I'm actually very curious about what if any bushings Rivian will use between the motors and skateboard and skateboard and body)
     
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  9. ajdelange

    ajdelange Well-Known Member

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    You are going to have to do better than value of time saved pumping gas plus cost of spark plugs to justify the purchase of a BEV. In fact you will probably have to throw out practical considerations altogether and buy the car or not based on emotional ones such as that they are a hell of a lot of fun to drive.
     
  10. Mr_funnypuns

    Mr_funnypuns Active Member

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    A great many people undervalue their own time, considering their free time “free”, when in fact it has a real value. https://www.clearerthinking.org/ Has an excellent tool for a rough estimate of free time, It uses comparative economic thought experiments to give a justification for a value for fee time. Depending on the assumptions I make about what constitutes work time, I get a value of between $100 and $200 an hour. This is not the economic value to someone else. It is instead my valuation of my time, and it’s the point where I’d be psychologically willing to trade an hour of my free time for cash, doing an activity that is neither pleasant nor unpleasant.

    Now you suggest we need to throw out practical considerations and (instead) buy a car on emotional considerations alone. But, how is personal enjoyment not a practical consideration? If, contemplating a purchase, I expect to enjoy it, I will pay more for it. If I don’t expect to enjoy it, I will pay lass for it. This is the very reason that free time is worth more than my time at the office... I have less of it, and enjoy it more. In the same way when considering a purchase, I would not choose a lesser value over a greater one when I have the opportunity to do so.

    Thus I am interested in the economic value of the decision to buy an EV, rather than the economic cost, and I’m interested in the question more broadly than just the Rivian truck, though I have put down $1000 for a place line to buy one. Plugs, gasoline, and time at the pump and maintenance avoided is important, and do in fact easily create favorable payback vs. a comparable gasoline powered truck I begin with this question, because I want to narrow the field: electric, hybrid, or gasoline. I want to know which is of the highest value to me. I suspect the answer is EV, and its “a hell of a lot of fun” to work at answering the question.

    The question of “what is the cheapest way to get to work” is different than “what is the highest value way to get to work”, and yet both are purely economic questions. The answer to the first question is a derivative of the answer to the second question. The answer to the first question is a straightforward cost per mile calculation, while the second question adds to it my own valuation of myself.
     
  11. ajdelange

    ajdelange Well-Known Member

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    You are trying to assign some sort of quantitative measure to what the pop sci folks call "warm fuzzys". It is, IMO, a pretty pointless exercise as it is so subjective. There are things about BEVs you'll love (the Tech, not having to change the oil) and things you'll hate (waiting for a stall at an SC, trying to contact Tesla for service, having to wait 3 months for a rocker panel) but as you don't know how many of negative events you will encounter a-priori you can't really come up with a meaningful numerical score unless you come up with ridiculous valuations such as what your employer would pay you were you at work insted of pumping gas or use the old lawyers "I was thinking about your case while I was pumping gas" trick and bill the client $450 per hour.

    In any case you won't save any time not having to pump gas if you waste time writing about it here. That calculus would certainly come up negative in my case. But clearly I get warm fuzzys by haunting these forums so the lost time is worth it to me by some subjective measure.

    You would do better to gobble up as much info as you can regarding the actual operation of BEVs by checking the equivalent of this site for Tesla, Bolt, i-Pace etc. to see what the downsides are and then decide if the pleasures of owning and driving one are enough to offset. Put it all in a spreadsheet if you want and base your decision based on that. Once you have a decision think about whether you are pleased with it or not. This is a trick often used to make tough subjective decisions though the input to the process is usually a coin flip rather than a spreadsheet.

     
  12. Mr_funnypuns

    Mr_funnypuns Active Member

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    I don’t know about warm fuzzies. But it is fun to engage, and enjoyment life has value. We have different methodologies for valuation, and both are comparative in nature. You advocate a non quantitative methodology. Sometimes that’s appropriate, such as whether to buy the chocolate or vanilla ice cream from Culver’s. But when the cost of a wrong decision is high, I find that I am much more successful when I apply a quantitative methodology to the decision. My estimate of the value of my time is an estimate. But it is as useful estimate.

    How far out of your way would you drive to save $0.05 a gallon? The answer depends on how you value your time. I’d never drive any distance to save the $1.25 difference it takes to fill my tank. Nor will I spend any more time discussing this point. I’ll concede the last word to you if you wish take it, and instead move on to assessing the reliability of EVs through published failure modes, battery degradation data, et. Al sources.
     
  13. ajdelange

    ajdelange Well-Known Member

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    #13 ajdelange, Nov 5, 2019
    Last edited: Nov 5, 2019
    That was the point of the Dilbert cartoon.

    No, I prefer things to be quantifiable but many times they just aren't. I spent a long career in engineering watching (and profiting from) people trying to quantify the value of things that basically can't be valued. Consider a simple example: a rutabaga. Suppose there is one between us on the table. What's it worth? At least we have a unit of value, the $. So how many $ is the rutabaga worth? If you are contemplating buying it from me we probably have different ideas about this. So we haggle and eventually we settle on a price. We have agreed on the worth of the rutabaga. So you take it home and your SO says "You paid X$ for a rutabaga? You fool! They sell for half that at the super market!" Now your assessment of the value of the rutabaga has changed. As another example consider the price of gold. It is set by emotion but at least there is a mechanism - the market - to establish a value even if it only holds for a few minutes.

    That works fine when you are, for example, choosing which FET your company should use in the inverters in it's EV's. But how do you quantify the reliability of the Rivian you are contemplaying plunking down $100 K for? Either Rivian will figure out how to avoid the disaster that is Tesla service or it won't. Even if it doesn't you may be lucky and not experience a failure that puts your car out of service for months. Or you may not. You can obviously try to figure out what the reliability of a Rivian by guessing at what transistor they will use etc. and if doing that gives you warm fuzzies then by all means, do it. But don't expect to get meaningful guidance from such detailed analysis. Were we talking optics I'd say such an effort leads to empty resolution. IOW IMO your estimate is not really useful. But if you enjoy the analysis, have at it! Just so you understand where I am coming from I have done thousands of such analyses. I've gained insight but that's about all.
     
  14. Joel

    Joel Well-Known Member

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    Don’t forget to factor in how bad the majority of the Majors (Ford, GM,VW,Volvo) are with software. My AUDI sq5 had at least 6 major software issues, two of which would regularly cause the car to go into limp mode or shut down completely. AUDI response was they are working on it. Four months after I traded the car recall notices started coming to my mailbox for those issues. My Volvo was just in for updates at the dealer which took 2 days and then it had to go back because part of the update failed. Talk about lost time taking a car to a dealer multiple times for software.

    My son has a Tesla m3 and there are things Tesla can definitely improve on build wise. But overall it’s a great car and we don’t need to go to a dealer for a software fix. That is the part I like about Rivian, Tesla, and any others that may pop up independent of the majors.
     
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