How much does aditional weight affect MPG

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Richter, Feb 13, 2012.

  1. Richter

    Richter Road Train Member

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    Hi everyone,

    I'm new to the forum and am looking at buying a used truck pretty soon. I want to design my own battery based APU since none of the stock ones quite get it right.

    So my main problem with stock ones is they don't have enough power for me to run everything I want. (heating, cooling, microwave, fridge, computer) The one made by idle free has 5.04kwh of batts and weights almost 400 pounds. Most apu's seem to range form 300-500 pounds. I'd like about 10 kwh of storage which weighs around 800 pounds. I could go with Lithium ion instead of AGM which would weigh only 250 pound for 10 kwh. lithium severely complicates the charging system and cost 3 times as much.

    So my main question is, will an additional 400 pound make any noticeable difference in mileage? Would it be worth going with a higher price battery and charging system to save 400 pounds?

    Thanks,
    Cody

    P.S. I've done the math and most trucks could easily charge over 10 kwh per day.
     
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  3. Cowpie1

    Cowpie1 Road Train Member

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    400 lb will not be noticeable on fuel mileage. Aerodynamics, tire rolling resistance, proper RPM engine range will do more for mpg than 400 lb. That amount of weight savings only would have an effect on the weight you haul.
     
  4. Richter

    Richter Road Train Member

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    Do most drives haul within 400 pounds of the max weight? I never thought about that as a concern. I'm new to trucking but can make a lot more driving my own truck. I think it would be a good move to own my own truck.
     
  5. JDP

    JDP Medium Load Member

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    Not to discourage you, but if you're new to trucking wait 2 or 3 years before you buy a truck. Get the experience as a company driver, live and learn, there are many more intricacies than meet eye. Better to learn on the company's dime than your own. I know what I'm about to say sounds offensive but I don't mean it that way. You said you haven't thought about the weight issue as it relates to decreased payloads. This is a critical aspect of the business and suggests you have a lot more to learn before become a business owner, not an employee.

    But to answer your question, it depends on what type of freight you're hauling. In my operation, I would not give up 400 pounds. 70+% of my open-deck trucks leave the yard grossing over 76K and many of them are that close to 80K that every bit makes a difference. Any weight savings for me translates to additional payload, mpg is not my concern from this aspect (though it is a concern, like cowpie said when speccing components) This is especially the case if you plan to haul bulk materials.

    400 pounds would not effect mpg significantly. If you're worried about mpg you should also take into account the year of the truck you're looking at. Trucks have increased significantly in weight and complexity over the last 5-7 years due to emissions regulations. This has hurt fuel economy much more than an additional 400 pounds.
     
    jimvrg Thanks this.
  6. Frenzy

    Frenzy Medium Load Member

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    My rule of thumb is that adding 1000 lbs will drop the mpg by .1.
     
  7. Richter

    Richter Road Train Member

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    Thanks for the input, especially you JDP. I'm certainly not buying a truck tomorrow but am trying to figure out projected cost so when i am ready I'll be good to go. (prob 6 months to 1.5 years) Your comment was not at all offensive. The reason I'd like to go to my own truck earlier then most is for fuel reasons. I have the capacity to create 1000 gallons of bio diesel per week made from used veggie oil. After paying for collection, road tax and making the fuel it cost about .65/ gallon and is a much greener fuel. So yes, your right, I'm not ready now, but I will be hopefully sooner then most. I'm a quick learner.

    In answer to the original question, it seems like mileage is not a concern with an extra 400 pounds, but overall weight is. Thus it would prob ebe better to save up for a better system
     
  8. JDP

    JDP Medium Load Member

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    Are you planning on running in a warm climate where you won't have the ill effects of cold weather on the bio diesel or do is there an additive to effectively overcome this?

    Do you know if bio diesel reduces your mpg? I guess even if it did significantly hurt it, at $.65/gal you're still going to come out ahead. Hell, lease on with a company that pays you 100% of FSC and your fuel only costs you $.15-$.20/gal roughly. That's considering you can do a round trip on one tank of fuel and you don't buy any OTR.
     
  9. Richter

    Richter Road Train Member

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    After I get some experience under my belt I'd hope to get a route in the southern states. Also trucks can be moded with aux tank heaters. Bio diesel does have a lower cetain rating but it lubricates much better. Because of the added lube, the engion doesn't work quite as hard. In my personal vehicle I get 1-3 mpg better with bio. Also the engiron will last tons longer.

    Posted from iPhone
     
  10. dancnoone

    dancnoone "Village Idiot"

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    Is this going to be a "self" made and installed system? Or a factory made/installed?

    Either way, I would be very concerned about carrying that large of a Lithium battery system.

    I'm all for long life batteries. Have lithium in most of the things I own. But the things have been known to blow up.

    And when they blow....it ain't pretty. Just mount them somewhere they will do the least damage.
     
  11. Richter

    Richter Road Train Member

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    They only "blow up" when over heated or broken. They can be safely mounted in a fire proof box. Although, I am seeign the limitations to a battery based system. It seems the Diesel based ones are a better option for OTR truckers.
     
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