# VW bug conversion



## rillip3 (Jun 19, 2009)

Sounds reasonable. 144v x 110 Ah = 14544 kwh, x .8 for DoD, x .8 for Puekert = 9.308 kwh. Estimate something a little high for an older (heaverier) unaerodynamic shape, say 350 wh/mi, you get a range of 26 miles. If that meets your needs, you're in good shape. If you want to go farther, you have to up the Ah, the voltage, or connect some cells in parallel.

Edit: see my reply below, I read this as VW Bu*S* not VW Bu*G*. Improved maths are below.


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## EVfun (Mar 14, 2010)

Check your motor and adapter total length. I think a regular 9 will fit using an adapter that retains the clutch, but that will be tight without cutting up the rear apron. You may need to use the Impulse 9 instead of the WarP 9 to clear the apron. Either motor will be plenty large to push the bug around.


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## terra (Mar 8, 2010)

That mileage won't do at all, I'm looking for closer to 100 miles. In my other thread I was recommended a 288v 160aH pack for 150 miles of range. Would cutting the voltage in half reduce my range then? I'm losing 50aH as well, but 150 miles to 25 miles is a huge drop.
Also, the bug weighs 1600lbs without engine and transmission.

I won't be using a transmission, so I'll do direct drive.


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## EV-propulsion.com (Jun 1, 2009)

There's a bunch of threads about why going direct is not recommended, but the bug is one vehicle that stands out as more difficult going direct than using the transmission since it has a transaxle. Adapters are readily available, and what would you use for a gear reduction if you are not using the transaxle? So why attempt direct drive?
Mike
www.EV-propulsion.com


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## Travdude (May 11, 2009)

It would be difficult to make a VW bug direct drive.

Here is one of my favorite videos that uses a similar set up to what you are planning.

http://www.youtube.com/watch?v=cz069B67gAo

Just for a point of reference, my VW bug has 40 TS 160Ah batteries and goes 60 miles at freeway speeds. You might get 80 miles with the SE 200Ah cells..


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## rillip3 (Jun 19, 2009)

terra said:


> That mileage won't do at all, I'm looking for closer to 100 miles. In my other thread I was recommended a 288v 160aH pack for 150 miles of range. Would cutting the voltage in half reduce my range then? I'm losing 50aH as well, but 150 miles to 25 miles is a huge drop.
> Also, the bug weighs 1600lbs without engine and transmission.
> 
> I won't be using a transmission, so I'll do direct drive.


Sorry, for some reason I had it in my head you were doing a VW bus, not a bug. We can easily cut that 350 wh/mi to 200. 9.308 kwh / 200 wh/mi = 46.54 mi.

And yes, cutting the voltage in half effectively cuts the range in half. volts x amps = watts. If you half the volts, or if you half the amps, you half the wattage, and thus you half the range.

The 200 wh/mi estimate is pretty optimistic, but it is a very light car after all. I wouldn't want to estimate any lower than that, and doing some math on Travdude''s bug bears that out.

Using Travdude's bug as a base, 128v x 140ah = 17920. X .8 for DoD, x .8 for Puekert, gives 11,468. So X wh/mi * 60mi = 11468. X = 11468/60 = 191 wh/mi. Pretty darn close to 200 wh/mi.

To get 100mi, you need 

200 wh/mi x 100mi = 20,000 wh x 1.2 x 1.2 (adjust for Puekert and Depth of Discharge) = 28,800 wh. To get this with 144v, you'd need 200 Ah batteries. To get it with 110 Ah batteries, you'd need 262 volts.


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## EVfun (Mar 14, 2010)

terra said:


> That mileage won't do at all, I'm looking for closer to 100 miles. In my other thread I was recommended a 288v 160aH pack for 150 miles of range. Would cutting the voltage in half reduce my range then? I'm losing 50aH as well, but 150 miles to 25 miles is a huge drop.
> Also, the bug weighs 1600lbs without engine and transmission.
> 
> I won't be using a transmission, so I'll do direct drive.


Good luck with direct drive on a Bug, I'm not sure how one would ditch the transaxle and come up with something more efficient. The VW transaxle is designed for efficiency and is a good choice when filled with modern synthetic GL-4 gear lube. Second and third gear rule, with a nice wide spread to take advantage of the flatter torque curve you will get with an electric motor.

My range estimates come in between 44 and 50 miles with 48, 110 ah cells that perform like ThunderSky or SkyEnergy cells. Make them 200 amp hour cells and you should be in the 75 to 90 mile range. Range more or less scales up and down based on how many watt hours in the car (pack voltage times amp hours) with a slight penalty for larger packs due to increased vehicle weight. 

One problem I see is that with this kind of potential range someone will want to do extended freeway runs at 60 mph or faster. The old Beetles are not aerodynamic so going faster than 50 mph will start to make a noticeable dent in range. I've owned 5 Bugs and love them - but they where never at their best on the freeway.


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## JRoque (Mar 9, 2010)

Hi. rillip3, excellent information and very complete answer.

I assume you arrive at the 200Wh/mi rate based on the vehicle's weight plus a bit more for aerodynamic losses. Do you also take battery weight into account? Meaning, a higher kW/h pack weighs more. Is that significant enough to skew the results much? How much does travel speed affect range? Or do you average out over typical speed range?

Thanks,
JR


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## Woodsmith (Jun 5, 2008)

EVfun said:


> Good luck with direct drive on a Bug, I'm not sure how one would ditch the transaxle and come up with something more efficient. The VW transaxle is designed for efficiency and is a good choice when filled with modern synthetic GL-4 gear lube. Second and third gear rule, with a nice wide spread to take advantage of the flatter torque curve you will get with an electric motor.


I would imagine placing a diff in place of the transaxle with a motor direct driving the pinion wouldn't be too difficult. Perhaps using a front diff from a 4x4 saloon or truck with IFS? I have seen off road racers using BMW 7 series diffs in the front with an IFS set up. 
But then there is the issues of gear ratios in the diff.


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## rillip3 (Jun 19, 2009)

JRoque said:


> Hi. rillip3, excellent information and very complete answer.
> 
> I assume you arrive at the 200Wh/mi rate based on the vehicle's weight plus a bit more for aerodynamic losses. Do you also take battery weight into account? Meaning, a higher kW/h pack weighs more. Is that significant enough to skew the results much? How much does travel speed affect range? Or do you average out over typical speed range?
> 
> ...


Pack weight does cause an effect, but it's not as linear and straight-forward. It does not affect your efficiency at cruising speed at all. A 10,000 lb truck and a a 1,000 lb car with the same CdA (coefficient of drag x frontal area) will have the same fuel efficiency, with all other things equal. While accelerating, the 1,000 lb car obviously has a major advantage. So it will really depend on your driving habits and environment as to how much extra weight impacts your vehicle. If you do a lot of city stop-and-go driving, it could cause issues. If you do a lot of sub-urban coasting with some occasional stops, it won't make a noticeable difference. The less you use your breaks, the less difference you'd see from the weight.

For the most part, unless you DRASTICALLY increase the pack size, most of the weight will come from the car frame and the previous batteries/components, so expanding a pack marginally is not a concern. For example, I was planning on a 96v conversion. That's about 58.6 x 8 = 468.8 lvbs. By going to 120v, I'm adding 117 lbs (adding 2 batteries), or the weight of one rather light person. In general, adding one person to a car won't significantly affect the range. But if I went up to a 240v pack, that'd be adding another 586 lbs, which definitely warrants recalculating.

The wh/mi is really just an eye-ball unless you take the time to really do a lot of math and/or measuring. Most people report in the mid 200's and low 300's. 300 is kind of the generic, average four seater car estimate.


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## corbin (Apr 6, 2010)

terra said:


> Just wanted someone to double check some work for me. I'm planning a conversion of a 1971 Bug. I was planning on the WarP 9 motor, with a 144v 110ah LifePo4 pack. I would use the Soliton1 controller. Am I on the right track?
> 
> Alex


Alex, I did a big analysis on this when I picked my components for my '69 bug. It is still in progress (batteries delayed).

See:
http://www.corbinstreehouse.com/blog/plug-bug/

for all my details 

corbin


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## mhud (Oct 19, 2009)

Is the 200 WH/Mile figure a measurement of battery current as it's sent to the motor? 

I measured my WH/Mile from AC during charging. Including charging efficiency and Peukert losses, I am close to 400 WH/Mile in my Bug. 

Restated hopefully more concisely, that is 400 WH/Mile to replenish my depleted batteries from shore power after a drive. 

Mine is a 120V Lead with a Curtis controller and Warp9. Half of my miles are stop and go city driving, 0-45MPH, the other half are low-speed highway, 55-60MPH.


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## mhud (Oct 19, 2009)

Terra, you are on the right track. The biggest thing I'd watch out for is the clearance for the motor. My H-Apron had to go. The RebirthAuto adapter plus the Warp9 motor were too big for my '73 Beetle, so I am going to have to fabricate some changes to a replacement rear apron.


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## rillip3 (Jun 19, 2009)

mhud said:


> Is the 200 WH/Mile figure a measurement of battery current as it's sent to the motor?
> 
> I measured my WH/Mile from AC during charging. Including charging efficiency and Peukert losses, I am close to 400 WH/Mile in my Bug.
> 
> ...


The charging energy will be very different than the discharge. Supposing for the moment that you discharge your battery 100% at discharge and charge to 100% each time. When you're discharging your 12v battery, you're using 12v. When you're charging your battery, you're using more like 15v. So the charging is going to be at least 30% higher, before the loses of the charger. 50% difference doesn't sound unreasonable at all.


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## terra (Mar 8, 2010)

Can someone just double check this math, 12 12v 450aH batteries using the 200wh/mi figure would get me a tad over 200 mile range correct?


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## corbin (Apr 6, 2010)

terra said:


> Can someone just double check this math, 12 12v 450aH batteries using the 200wh/mi figure would get me a tad over 200 mile range correct?


I'm pretty sure your math is not right. If you are using 12 lead acid batteries, then your weight is going to be very heavy, and you will not be getting 200wh/mile.

Where did you come up with these figures?

corbin


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## terra (Mar 8, 2010)

corbin said:


> I'm pretty sure your math is not right. If you are using 12 lead acid batteries, then your weight is going to be very heavy, and you will not be getting 200wh/mile.
> 
> Where did you come up with these figures?
> 
> corbin


144v*450aH*.8*.8=41,472

200wh/mi

41472/200=207mi.

Go up to 300wh/mi and it would be 138mi.


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## rillip3 (Jun 19, 2009)

Okay, when I made my estimates, I was thinking something like 150 Ah batteries, something in the fairly common range. The weight on 450 Ah batteries is outrageous - 332 lbs each. x 12 = 3984 lbs. Your batteries will weight significantly more than the entire car. Like close to 2x the weight of the car, maybe a bit more. No way the suspension/frame can come close to handling that kind of weight. The only way you could get that much kwh into the vehicle would be lithium, and it'd still be a tough fit.


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## terra (Mar 8, 2010)

I've found some for WAY less than 400lbs each.

But thanks.


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## corbin (Apr 6, 2010)

terra said:


> I've found some for WAY less than 400lbs each.
> 
> But thanks.


They would have to be about 80/lbs each to get that low of watts/mile, considering 1000 lbs of total batteries (which would exceed gross vehicle weight by a few hundred pounds).

I think you'll need to do some calculations involving the weight of the vehicle compared to the batteries to get a more accurate watts/mile guess, and not just use 200w/mile.

-corbin


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## frodus (Apr 12, 2008)

terra said:


> I've found some for WAY less than 400lbs each.
> 
> But thanks.


Maybe he didn't know you were using lifepo4. 

Lets use for example some 400Ah TS batteries, which are about 30lbs each. Normally people do 48 in series for a ~144V system. Thats almost 1500lbs in batteries alone. Add to that the motor, charger, controller and other stuff, and I bet you're around 1700lbs. Thats more than what you said the weight of the rolling chassis is. You're doubling the weight of the car. Its going to handle much differently, accelerate slowly and you'll spend a bit of money getting the suspension too handle all that extra weight.

Also, I'm not sure if you've looked at any dimensions, but these 400Ah TS cells are ~18" long, ~11" tall and ~3: wide... so about 0.35cubic feet. You realize thats over 16 cubic feet for that many batteries? Thats a 4' x 4' x 4' box. Do you even have that much spare space in the vehicle?

Then we get to price. Lets say the going rate is ~$1.40 an Ah. You're using 48 batteries, 400Ah.... thats about $27,000.

Yes, it would take ~42kwh to meet your needs of range, but you really need to consider all of these things simultaniously. Cost, weight and space considerations are major.


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