Räckvidd mot fart 2

I det tidigare inlägget ”Räckvidd mot fart” förklarades att höga farter innebär begränsningar i räckvidd. Vill man åka långt gör man bäst i att hålla ner farten. Inlägget blev en veritabel succé och genererade frågor om förhållandena är desamma i låga farter och det har vi nu testat i del 2.

I första inlägget testades skillnader i konsumtion mellan 80, 100 och 120 km/h. Testerna gjordes med samma vägsträcka, vind, temperatur, etc. Bilen sattes på farthållare i alla tester. Det visade sig att strömförbrukningen ökade 25% när farten ökade från 80 km/h till 100 km/h och vid 120 km/h var den mer än 50% högre.

I del 2 av testet har vi nu prövat skillnaden i konsumtion mellan 40, 60 och 80 km/h. Även den här gången var förhållandena desamma och bilen kördes med farthållare i de angivna farterna. Det visar sig att även i lägre farter är skillnaden i konsumtion markant. Bilen drar 15% mer energi vid 60 km/h jämfört med 40 km/h. Vid 80 km/h har förbrukningen ökat med 40% jämfört med vid 40 km/h.

Det var av praktiska och säkerhetsmässiga skäl svårt att testa de låga farterna på samma vägsträcka som de höga farterna men eftersom förbrukningen vid 80 km/h var nästan identisk i de båda testerna har jag kopplat ihop dataserierna. Av det kan vi dra slutsatsen att förbrukningen är 120% högre vid 120 km/h jämfört med 40 km/h!

Power Consumption at different Speed

Om vi precis som förra gången räknar om förbrukningen till räckvidd blir resultatet mer intressant. Om vi tänker oss att det givet en viss temperatur, vind, vägsträcka etc finns tillräcklig laddning i batterierna att kunna köra 100 km i 100 km/h så går det att köra ca 25 km längre om farten sänks till 80 km/h. Vid 60 respektive 40 km/h kommer vi då 155 respektive 180 km.

Range at different Speed

Förhållandet visar sig vara nästan linjärt och planar endast ut mycket marginellt i låga farter. Slutsatsen blir därför att om man är intresserad av att slå räckviddsrekord med en i3 så ska man köra i snigelfart. Behöver man åka långt och vill komma fram snabbt är det dock säkert en bättre strategi att köra fort och ta en pausa på 20 minuter vid någon snabbladdningsstation.

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14 reaktioner på ”Räckvidd mot fart 2

  1. Having driven my i3 for the last 4 weeks, your findings are absolutely true.

    This vehicle is best at speeds under 90km.

    The Eco Pro Plus is far more effective than I realized, especially in highway stop & go traffic.

    Leaving in comfort mode, I could’nt believe how quickly the charge disappears.

    If your willing to work with the settings, on going, what a huge difference.

    Love my car, was expecting better range overall. Learning curve like anything else.

    1. What was the test distance here? I’ve driven mine i3 from south of Norway up into the mountains E6/E16 and from mine experience i3 has much lower consumption over longer distances. Some examples:
      70 km distance at +90 km/h -> 12.5kW/100km
      100 km distance at 70-80km/h -> 13.3kW/100km
      70 km distance at +100 km/h -> 15.8kW/100km

      1. Additional comment to the low 12.5 kW/100km consumption:
        The 90km/h distance: flat highway
        The 70-80 km/h distance: a lot of up/down hills

        1. Hi Geir,
          It is important to underline that this was never an attempt to measure consumption or range. It will be very different depending on road, temperature, etc. The only thing measured was the difference in consumption at different speeds.

  2. Hi,

    I just bought an BMW i3 (waiting for it by the end of may) and after I discovered your page and I became quite curious because you mention this – as far I can unserstand:
    40 km/h – 10kwh instant consumption => 100km x 10kwh /40kmh = 25kw to make 100km?
    120km/h – 23kwh instant consumption => 100km x 23kwh/120knh = 19kw to make 100km?

    Or you drive for 100km and the total consumption at 40kmh was 10kw? meaning an instant consuption of 10 kw / (100km /40kmh) = 4kwh?

  3. I travel to and from work 100km each direction everyday. And 80 of them is at 110km/h.
    I use about 17.8-18.5Kwh at this speed. In comfort and with very cold i have to REX 5min.

    But normally i reach work at 7-10% charge left. And since it cant fully charge during a whole day on 230 charger i leave at 95% and most days reach home at 6% with REX autostarted. Since i travel highway that much i dont regenerate any energy at all wich impedes distance.

    Nowdays i dont do 140 on our 110 roads like ive done the last 20 years before….. 😉

      1. I was using about 0.5 litres/day
        After update of software in car i dont Rex anymore except when weather is very cold. When i wrote post i had only had car for 2 months, but now after another 14months i learned alot and drive mostly in Eco-Pro mode. This gives about 25 more kilometres. Commfort mode i use when i drive locally or want to drive a bit ”manly”….

        Done 51000Km in the car now. I love every minut in it and will NEVER NEVER go back to a fossil car.

        As an added bonus here on the west coast in Sweden many municipalitys have a free rapid recharger available.

        I calculate my use of gasoline so far is about 250litres.(0.6l/10km) Mostly used on long distance travelling during vacations.
        Something i have noticed when i meet leaf owners and Zoe owners on charging stations is the fact i recharge my battery from 5% while they usually have about 20-30% charge in batterys when they charge it.
        REX is a big winner for sure.

        1. Thanks, very, very interesting !!! So, even in Comfort mode, you can expect 15 to 20 km per liter of extra range, quite impressive !

  4. If consumption is, indeed, proportional to speed, there is an interesting mathematical consequence.
    For a fast journey, drive for half the time and charge for half the time.
    This assumes there is no initial charge (or the journey is long) and no speed limit.

      1. Yes, I noticed that after I posted.
        You are talking about a practical problem using rapid chargers as they actually work, and doing a thorough job.
        I am talking about a theoretical observation, which may provide some insight.
        (I am also assuming that chargers charge at constant rates, which they don’t.)
        Here in Ontario there are very few rapid chargers. So the quickest way to get a long way might be to drive at 60 kph, maybe on back roads to be safer.


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