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Discussion in 'Automotive' started by HadACoolName, Mar 6, 2015.

  1. default0.0player

    default0.0player
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    Battries have finite lifetime. Assume you have a battery that is rated 500 cycles lifetime. If you do 20%~80%~20%~80%~20%~80%~20%~80%~20%~80%.... Then you got about 1000 cycle lifetime, Still way lower than infinite.
    --- Post updated ---
    This is about internal resistance, most li-ion battery is rated 3.0V~4.2V voltage, the perceived voltage is higher than actual when charging, when the perceived voltage reached 4.2V the charging speed goes down even though the actual voltage is still lower than 4.2V, otherwise you risk overcharging the battery. Similarly, EVs will lose horsepower when the battery is lower than 20%, which don't happen in ICEVs.
    --- Post updated ---
    No, it's not about political "ism"s, its about cost effectiveness, when they use EVs batteries as a ballast to "balance" the power plants. They'll immediatly notice that their plants are working more efficiently, but it'll take years to be noticed, the cost of replacing dead batteries(battery has finite cycle lifetime) is way, way higher than the cost saved by running plants at a slightly higher efficiency. Sadly those polititians don't even know about delayed gratification.
    Also, when doing this, EV owners have to plan their livings in advance, so this scheme is acturally restricting user freedom.
     
  2. SixSixSevenSeven

    SixSixSevenSeven
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    Actually, incorrect. Yes, batteries have a finite lifetime. But over 90% of their wear is sustained when discharging below 20% or charging at a high rate over 80% (both regions in which dendrite formation occurs). Resulting in a 500 cycle battery that is being run 20-80 constantly potentially exceeding 5000 cycles, not 100. Combine with how there are Tesla's coming up on 100000 miles already (there's one in the work car park with such mileage) with under 5% wear, or, still having 95% of their original capacity and range.

    Batteries only have a finite lifetime due to wear, the wear can, and is, actively reduced.
    The recommended default setting for tesla charging is to only charge to 80%, though if a user requires more, the settings can be changed and it can be triggered on a once off. That alone hugely reduces the wear, and hence, increases lifetime.
    internal resistance is very constant throughout discharge of a battery and not the reason for horsepower loss, that is simply loss of voltage. Nor is it to do with perceived voltage. But it does link to internal resistance in a different way. High charge rate with high internal resistance results in heat. High charge percentages, the battery isn't actually in a particularly chemically stable state, heat+instability is just a catalyst. You find batteries wear much much harder, you find risk of explosion is much much higher. It's not stopping overcharging (though that's important too), it's reducing of battery heat. You actually hit that perceived 4.2 far later in the charge cycle than 80%, but you still need to cut back earlier. I have built a DIY 3 stage lithium charger before with a recovery stage, constant current bulk charger and then the finally constant voltage top off.


    Some of these demonstrated 200kw+ charging EVs like the taycan are even actively cooling the cells to do it. Some of the others (Tesla roadster and semi) simply get away with it due to so many cells in the system that the charge rate per cell is still quite reasonable (which for both mentioned vehicles, again required as internal resistance does limit peak currents you can pull from cell, more cells in parallel, more current, more power, haul a trailer or accelerate at ludicrous speeds). It's an interesting point though, the bigger the battery, the more power you can safely charge it with, total charge time might still be the same but miles gained per minute of charging may be higher.
     
  3. GotNoLimbs!

    GotNoLimbs!
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    Your knowledge hurts my mortal mind
     
  4. default0.0player

    default0.0player
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    Well, that's LiFePO4 batteries.
    Perceived voltage has something to do with internal resistance. Perceived voltage = actual voltage - (current X internal resistance), where the actual voltage depends on battery levels, current depends on gas pedal and internal resistance depends on temparuture.

    As shown in the picture, the higher the current, the lower the perceived voltage at the same battery level.
    echarging.png
    The internal resistance has two parts. The physical one is the resistance of the anode/cathode itself, the chemical one is the voltage difference of moving electrons in the electrolyte when charging or discharging.
    Therefore, if you stop the charge when reaching 4.2V at the first time, the voltage will drop to 4.1V right after stop, then slowly drop to 4.05V when the chemical balanced. Smart chargers can calculate the internal resistance and apply a higher than 4.2V voltage, after charging the battery will be higher than 4.2V then slowly drop to 4.2V so no overcharging.

    Therefore, you cut back later than reaching 4.2V, not earlier.
    If you just want to charge to 80% for longer battery life you can constant current to 4.2V then immediatly turn off the charger.

    Also keep in mind that it is NiMH battery, not Li-ion battery that heats up when close to 100% charge, due to the recombination process.
    That's nothing. Battery charge/discharge in rated by C number. If a battery has 10Wh, charging at 20W is 2C charging. Modern high-current batteries such as those in radio-controlled scale models, can handle 90C discharge rate and 15C charge rate. Those batteries are expensive as hell, if you put them into an EV you can get the vehicle ready to go in under 5 minutes, however it would require 1.5MW to do that. Refuel an ICEV is different, you transfer the energy by moving the fuel, which does not require high-powered machines.
    200kW charging a 100kWh battery pack is only 2C charging, even flashlight batteries can easily do that.

    Unfortunately, the more the battery, the heavier the vehicle, the lower the mile per kWh.
     
    #16004 default0.0player, Oct 17, 2019
    Last edited: Oct 17, 2019
  5. aljowen

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    I am pretty sure that Tesla uses the exact same cell size and chemistry as flashlights and lots of other electronics (e-bikes, certain laptops, battery banks, swegways, vapes, etc). (Ofc there are many grades of battery quality, Something generic out of China will be in a different league to a Samsung or Panasonic)

    IMG_20191017_150043__01.jpg


    So it seems a bit overly derogatory to state "even flashlight batteries" as if they are some sort of different breed. The lipo batteries used in RC cars can discharge/charge quicker etc, but they have their own problems, and there is a reason why many RC car clubs require them to be charged in fireproof bags.
     
  6. default0.0player

    default0.0player
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    Cell size =/= chemistry. Of course you can use high-current battery in a flashlight but it's not needed.
    There four types of battery classes. Cheap, high-capacity, high-current and balanced.
    Cheap batteries are, well, very cheap, such as those 18650 only rated 2000mAh and 1C discharge.
    High capacity is those Panasonic NCR18650B rated 3250mAh, 2C discharge and 0.6C charge.
    High current batteries have lower capacity but high C ratings, a good typical example is the Sony VTC5 which rated 2600mAh and 30A discharge.
    Balaced batteries are about 2850~3000mAh and 3C to 5C discharge rate.
    The flashlight battery shown in your picture, the INR18650-25R is between balanced and high-current class(2500mAh 8Cdischarge).

    Non of the EVs are using high-current batteries.
    AFAIK Tesla Model S is using the Panasonic NCR18650PF or NCR18650BE that is only capable of doing 2C-2.5C discharge.They put two motors with a combined power of 592kW, which is not good for the batteries.

    E-bikes swegways:Mostly cheap batteries
    Laptops, batterybanks: Cheap or high-capacity depends on quality.
    vapes: high-current.
     
    #16006 default0.0player, Oct 17, 2019
    Last edited: Oct 17, 2019
  7. SixSixSevenSeven

    SixSixSevenSeven
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    Cba to actually break this down, but there is a lot up here that is just outright wrong, or you have deliberately misquoted me, one or the other. I suspect the prior when you are using graphs that demonstrate a completely different point than you are arguing. A discharge graph of voltage drop due to ESR under load has nothing to do with charging circuitry.
    *All* batteries get warm during charge. NiMH gets warm while *held* at charge, that isnt during charge though. Note, smart chargers also have a temperature sensor in the battery to track such things.


    I have literally constructed lithium battery chargers. I work in the electronics industry. I am well aware of C ratings. You appear unaware that samsungs 2C recharge cells are also rated for a *peak* 2 C charge and are recommended to be charged far far slower, with recommendations from samsung themselves to taper charge rate off at high or low states of charge and only use 2C rates during the bulk portion of the charging cycle. This can also be witnessed in basically every charging circuit under the sun, besides that TP4056 single cell charger from china that sometimes crops up in tiny devices that are so cheap as to be disposable.

    Wear is *not* linear.
     
  8. vmlinuz

    vmlinuz
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    Alabama turbo



    Alabama turbo
     
  9. Potato

    Potato
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    This video is inspiring to me. I want to recreate it but I'm scared.
     
    • Like Like x 1
  10. redrobin

    redrobin
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    I genuinely feel that hydrogen is a legitimate way forward. It's literally the most abundant element in the universe, is friendly to jolly polar bear, and has the convenience of ICE.

    You'll never see me be in favor of a 100% battery electric car, but I'll absolutely back a hydrogen fuel cell.
     
    #16010 redrobin, Oct 19, 2019
    Last edited: Oct 19, 2019
    • Agree Agree x 1
  11. SixSixSevenSeven

    SixSixSevenSeven
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    Honestly most of the arguments against hydrogen apply to pure battery, so yeah, I guess I agree.
    Biggest upside of an EV over hydrogen is charging at home, but there's even been proposals for hydrogen/battery hybrids kinda giving you best of both worlds
     
  12. skodakenner

    skodakenner
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    the other good thing about hydrogen is that it works easily with Lorrys and ships as well. Also you can use your hydrogen car for powering your house as well. Or like Hyundai wich is planning to sell the hydrogen part of theyr iX30 as a power generator for citys.
     
  13. HadACoolName

    HadACoolName
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    Do it plz
     
  14. skodakenner

    skodakenner
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    Just realized that you can now buy a Ford Explorer in europe but it costs 74 grand wich is pretty expensive imo if it wants to succeed against other 7 seaters here. For example a 7 seater Skoda costs 30 grand yes it doesnt have the space of the explorer and not the engine but its way easier to use here cause you can park it. Also a Audi Q7 costs nearly the same as a Explorer but the Explorer has alot of kit as standard.
     
  15. Harkin Labs Gaming

    Harkin Labs Gaming
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    Why are they charging so much for it. Here in the states, the base trims are less than $30,000, which is even less than the Skoda you are talking about if you factor in exchange rates. I don't think you can even option out a Ford Explorer to cost more than $65,000. It doesn't make much sense to me because Explorers aren't well built, luxurious, or have any other features that would make someone want to pay that much money for.
     
  16. aljowen

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    Its worth noting that prices in Europe are typically the "on the road" prices with no hidden fees. So the price they quote is the price that you pay including sales taxes. Its also fairly rare to pay list price, but I assume that is the same in the US. Most dealers will automatically give you 5-10% off when they give you a quote.
    Taxes on car sales within Europe vary quite a lot, some countries don't tax emissions very much, whereas in others the price of certain cars can double based upon value and emissions. So if that explorer is using a US spec engine, in some European countries that could bump up the price considerably, in others it may not make any difference.

    With all that said, cars brought to Europe from the US typically don't make a whole lot of practical sense. They have never been brought over in quantities large enough to provide a cheap supply of spare parts. They are almost always a bit more expensive than they should be, and they are not tailored to meet local demands (or around local tax laws for some countries). For example, most people in Europe learn to drive in a manual transmission car, so when they go to buy their own car, they typically want to buy a manual. Equally, fuel economy is often one of the key selling point of cars in Europe, whereas US designed cars traditionally tended to fare a little worse in that regard since they make different compromises to suit their target market.

    To give an older example, the Chevrolet Lacetti was between £11k-£13 when new. Yet you could get a Peugeot 206sw for between £8k-£14k
    The Lacetti got between 32-39mpg(uk) depending on model, the Peugeot got between 35-64mpg(uk) depending on the model.

    Both are pretty bland normal cars, so what reason was there to spend potentially £3k (22%) more on the Lacetti?
    upload_2019-10-20_13-0-36.png
    upload_2019-10-20_13-0-54.png
     
    #16016 aljowen, Oct 20, 2019
    Last edited: Oct 20, 2019
  17. Harkin Labs Gaming

    Harkin Labs Gaming
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    I didn't really know that cars are taxed so heavily over there. I agree that cars built for the US are designed for the specific needs of US customers, and don't necessarily work well in other environments.

    What I find interesting is that I have never heard of or seen a Chevrolet Lacetti. I believe it is a Mexico/South American market car. It looks similar in size and appearence to the Chevrolet Aveo, which wasn't a great car.
     
  18. aljowen

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    No idea, I just assumed that with an interior like that, it clearly wasn't designed for a European market

    More info here: https://en.wikipedia.org/wiki/Daewoo_Lacetti
    So in the US it was sold as a Suzuki. Apparently Pininfarina did the styling...
     
    #16018 aljowen, Oct 20, 2019
    Last edited: Oct 20, 2019
    • Informative Informative x 1
  19. MrAnnoyingDude

    MrAnnoyingDude
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    Polish Ford site tells you to wait until 2020 for pricing.
     
  20. aljowen

    aljowen
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