# Range



## dougingraham (Jul 26, 2011)

The rule of thumb is to take the weight of the vehicle in lbs (with driver) and divide by 10. The number that comes out of this is the estimated watt hours per mile. In your case it looks like around 1800 lbs so 180 wh per mile. In order to make use of this you need to know how many watt hours your battery pack is. Your nominal voltage is 72 and the batteries are 100 AH so you have a 7200 watt hour pack. 7200/180 = 40 miles. That seems pretty good and it would be if it was true. If your batteries were lithium you would most likely get close to that and the car would weigh 200 lbs less. The problem is you are talking about Lead Acid batteries. The 100AH rating is for a 20 hour discharge. To get your 40 miles you would have to drive no faster than 2 mph. If you try to drive that 40 miles at 40 mph which would be a 1 hour discharge you lose about half the capacity of the cells. So at reasonable speeds your range would be 20 miles. And with Lead Acid it gets worse. In order to get reasonable life from the Lead Acid batteries you can only use half of the capacity or they degrade quickly. This puts your lead acid range at 10 miles. If you take good care of them at drive no more than 10 miles per charge you could expect that at the end of two years your range would be about half.

Since you have all of this stuff already I suggest you build the car and drive it until it needs new batteries or you discover the range is not what you need. Then replace them with an equivalent weight in Lithium cells.

Best Wishes!


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## ratrog64 (Dec 10, 2014)

So, you mean to tell me that all of these guys building ev beetles with regular deep cell batteries and 72 or 96 volt systems are only getting about 10 to 15 miles per charge? No wonder there are so many ev converted beetles for sale for pennies on the dollar!
Seems to me that unless you are willing to spend 6 to 9 k on batteries, there is really no point in doing an electric vehicle.

Thanks for the information!


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## dougingraham (Jul 26, 2011)

If you do a 96 or 144 volt system with 100AH batteries a couple of things happen.

1) You have more range because you have more energy although it is hurt a little by the additional weight. A 144 volt system would have twice the range of a 72 volt system if it weighed the same.

2) You have more range because the average battery current is reduced which lessens the capacity loss due to the higher currents.

Another thing to take into account is that for a lot of people a 15 mile range would be plenty for a grocery getter. I spent three month before I did my conversion monitoring my daily drives and discovered that my average day was only 12 miles. And surprisingly my longest day was 28 miles. People think they drive lots more than they do. I know I did.

As to the $6k to $9k on batteries, you get all of that back in fuel savings over a 3 to 6 year period. Depends on how much you drive and the cost of gasoline and electricity. Compare a vehicle that gets 30 mpg with an EV that gets 180 wh/mile. At todays price of gas of $2.50 a gallon you will get 12 miles per dollar spent on gasoline. At todays price for electricity of $0.12 per kilowatt hour you will get 46 miles per dollar spent on electricity. That is traveling 3.8 times farther for that dollar spent. If gas goes up to $4 per gallon again the ratio is 6.13 times farther driven on a dollar.


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## madderscience (Jun 28, 2008)

... and if you go with lithium instead of lead, you don't have to divide by 2 for realistic maximum range, or by 4 to let the batteries last more than a couple of years. Instead, a conservative rule of thumb is 70% of rated capacity, e.g. if you get a 100ah pack, you can use 70ah and have plenty of margin. The only other consideration with lithium is to make sure you have enough C rate, e.g. even if a 60ah pack will give you enough capacity, if you will need 500A to accelerate then those cells may not be big enough. 

However, in an 1800lb VW chassis you can go pretty small and still be OK. There are a couple people in my local EV group with similar vehicles to what you are considering with 60ah, 144v packs which work just fine.

Its also worth pointing out that generally speaking once you replace your lead acid pack the first time, you could have bought a better lithium pack up front for about the same amount you spent on two lead acid packs.

If you don't like the prices now, stow the conversion kit for a couple years, and keep an eye out for surplus nissan leaf cells, they are only going to get cheaper over time.


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## PStechPaul (May 1, 2012)

I used my http://enginuitysystems.com/EVCalculator.htm to find that a 1600 lb vehicle going 31 MPH on a 1% slope needs 4.8 HP and uses about 116 Wh/mile, so your 7.2 kWh battery pack (derated to 40%) would possibly provide a range of 7200*0.4/116 = 25 miles, and that does not take into account the efficiency of the mechanical and electronic components.

Climbing a rather steep 10% slope at just 3 MPH takes just 1.6 HP (assuming you have a good low gear for the torque) and it will use almost 400 Wh/mile.

If you want to cruise on level ground at 50 MPH it will take 7.4 HP and use 111 Wh/mile.

For the 5 HP (3.8 kW) condition the 72 volt system will pull 53 amps or about 0.5C for 100 amp-hour batteries, which makes them effectively 59 A-h and the pack will have 4200 W-h and about 3200 at 75% discharge, so again we have 3200/116 = 27 miles. 

YMMV.... HTH


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## Yabert (Feb 7, 2010)

PStechPaul said:


> that does not take into account the efficiency of the mechanical and electronic components.


This variable can change the result a lot... especially if his 72v kit include a small and not efficient 6,7'' motor.
Those tiny motor has bad efficiency when they are overloaded.


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## ratrog64 (Dec 10, 2014)

Thanks for the additional input. Something in the 20's sound more interesting to me. I was going to shit can the whole electric idea yesterday morning and just put a VW motor in the car and finish the project. Then after getting up to my shop I said WTF, just commit and do it! What ever it is it will be. After selling off the car and other parts I got with the purchase I will have next to nothing in the electric part of the conversion including the batteries. The building of the chassis and body I do for the pleasure of the build and the creative outlet. I'm not doing this to save the planet, or to be my daily driver, more because I have the parts and I love working on VW's. The part of Florida I live in is very flat and I don't have to deal with cold batteries. My shop and the few local businesses where I spend my money are pretty close, so if I end up with nothing more then a street legal glorified golf cart, so be it!


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## ratrog64 (Dec 10, 2014)

The motor is the D&D Series ES15A6 72volt and the controler is the Altrax 7245pm. The batteries are of an unknown brand 12volt AGM 100ah I believe.


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## piotrsko (Dec 9, 2007)

There are pretty much only 4 FLA battery makers in the US anymore. If the batteries weigh about 40 lbs they are starting batteries. If they weigh 60 lbs, probably "deep cycle" marine, especially if they have 5/8-16 studs. If they weigh more than 60 lbs, they are true deep cycle long life. Since about 1989, everyone has been putting date of manufacturing labels somewhere.


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## GoAhead92 (Dec 16, 2012)

My experience with a lead pack was a range of 18 miles when new running a 96 volt system in a 2500# car at speeds below 40. This was to a discharge just past 50%. While I din't really want lead, that came with the NEV. So I drove it for a year & 3K miles before the range deteriorated and I switched to LiFePo. 
I recently purchased EVTV's older generation SE CALB cells at $85 each for 100 AH cells. For me, the weight savings was around 500#s though early range testing hasn't really approached the 40 miles I was expecting. If you switch to lithium, most likely your charger will need to be reprogrammed to work correctly.
But here's my point on range & energy use. The driving characteristics & acceleration rates have an even greater impact than I expected. For me, staying with or in front of the traffic flow from a stop draws 250 - 300 or more amps. Comparing this to a 'hyper-miler' gentle acceleration where I draw only 100 - 125 amps shows a great impact on range. Both will bring the car up to speed, but the later can impede traffic flow. Similarly, driving 50 mph uses much more, not exactly 2X, as 35 mph. For me, driving habits impact my range by a third or more.
I hope this info helps align your expectations with what you'll experience. I'm looking forward to some pictures and updates.


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## ratrog64 (Dec 10, 2014)

So I have been driving the car for about a week and a half. I started out with the battery pack I got with the car while I am still in the mock up stages with the car. Using the pack I got, which is 6 12volt AGM of an unknown name and age I was only able to put about 2 miles on the car before it was really beginning to slow. I recharged the pack and did the same about 3 or four different evenings at my shop. Just making runs up and down the street. What this has done for me is tell me that the car drives ok, handles ok, and I don't really need to alter anything other then I added some coil over shocks in the rear and front. I knew I would use coil overs up front because I wanted the look, and I figured I would need them in the rear because I softened the rear suspension. So no surprises other then how much fun it is to drive.
So now that I know all is as it should be I bit the bullet on Monday last and bought 6 new Trojan 1275 batteries. This car has limited space so the 12 volt pack is really all I can do at this point besides maybe Lithium which i won't spend the money on for a toy. I have been making runs up and down the street where my shop is and the pack seems real good. I don't have any lights connected or a tag so I am limited to how much or how far I can drive. I am waiting for my volt and amp gauge to be made and delivered from Westach so I am unsure about how my pack is doing. I downloaded a gps speedo on my phone and have gotten the car up to 40 mph so far. I don't expect much more then that so it will be mostly a neighborhood type car.

I am going to post a link to a youtube video of the first ride. This was taken with my phone at my shop before I finished the brakes and with the original pack. And yes I know its not wise to drive without brakes so before all the armchair safety supervisors chime in I will say save your comments for someone who cares.  

Also keep in mind, this car is still in the mock up stages and will remain a rat rod when finished. And yes it does have brakes now!

http://youtu.be/RJrEcwpmJeI


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## PStechPaul (May 1, 2012)

Looks like fun! Catching some rubber in reverse is impressive. Good luck with your new "toy"!


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