# VW Super Beetle Conversion Question



## tony3811 (Jul 30, 2010)

Per the sticky:


Your skill level with auto mechanics and fabrication:
Built two track cars, good at welding, body work, and general ICE knowledge. Not so much experience with EV electronics, especially when it comes to terminology and calculations.
 


The range you are hoping to get (how many miles/charge):
40 miles at 40 MPH
 


What level of performance you are hoping to get
Daily driver commute to work, little to no traffic at 8 miles each way, over rolling hills.
 


How much money you are willing to put into your project
As little as possible to get the desired performance, not to exceed 5k for the remaining parts.
 


What parts you've already considered, if any.
See below
 

Hi everyone, I need with my current EV project that has been sitting in my garage for almost two years now. I want to finish it by next spring, and I need some advice. Please Help! 


What I have: 


1978 VW Super Beetle Convertible (All ICE components removed)
Upgraded to Disc Brakes
All body work done, car painted, and ready for EV parts
Warp 9 Motor (Dual Shaft)
EV Tranny Housing (retains stock tyranny and clutch assembly)

What I want: 


I want to be able to commute to work daily in favorable weather, (8miles each way over rolling hills).
I need to drive up a large hill to get to my house at the end of the day.
I don't need to exceed 50 miles an hour, though generally I would like to get 40 miles at 40MPH.

What I know: 


Lots of people have done lots of VW conversions, and most are successful, though no one really seems to want to admit what their range is.
There are many options to choose from and no one really has "the best option"
Batteries can be expensive

What I am planning (make a suggestions on alternatives if you would like)


Belktronics 120V 500 AMP controller w/battery monitoring
Suspension Upgrade
Battery Purchase (either Deka Gel [$250 each need 10] or CALB LiFe04 100Ah [$122 each need 38])
Misc electrical connectors/parts

The advice I need:


Which batteries do you think I need to get for the range I'm looking for? LiFe batteries have come down a bit and the price is almost reasonable, but I don't know what the Amp Hr rating should be for my application. Do I need 100AH with this, or is a 60AH rating going to work for me (I just can't seem to find the info or a relevant EV calculator anywhere)?
Do I really need a 120V system or is 96V going to be enough?
Am I missing something

Thanks for the help!


----------



## madderscience (Jun 28, 2008)

So you have a good chassis and a nice warp 9" motor and adapter plate already, and you want 40 miles maximum range at 40mph on a budget of $5K for the remaining parts.

Lithium is definitely the better battery technology these days (and you would not need a suspension upgrade if using it) but you will have trouble squeezing it along with everything else into a 5K budget by the time you include BMS, etc. You would need 100AH cells at 120V to have enough range, and that would end up being your 5K right there.

I would avoid Gel, sealed, or AGM lead acid batteries. Yes, they are "maintenance free" but they are more expensive and you get fewer cycles out of them, and they are much easier to damage via excessive discharge vs. flooded lead acid. 

So for the battery, how about ten 12V flooded golf cart batteries (trojan T-1275) for about 8KwH usable battery capacity in 800lbs or so. Pack will end up costing around $2K for the Trojan brand. If you can get about 200WH/mile which should be quite doable at steady lower speeds in a beetle with a total gross weight under 3000lbs, then there is your 40 miles. So you should have plenty of margin to get up your hill after a 16 mile commute even as the batteries start to age a bit. With lead acid, you will have to budget for a new battery pack every 3 to 5 years though.

Not too familair with the belktronix controller but its basically the same specs as the curtis 1231, which is no hot rod but works fine in smaller cars. you'll have freeway capability if you want it.

As for actual range numbers, while my car isn't a beetle it is similarly sized but probably heavier than what you will build, weighing 3400lbs as converted (1250lbs of FLA battery), and I can get low 200's wh/mile in real driving on longer trips including significant rolling hills and speeds 40-50mph with few stops. case and point, averaging out four recent 36 mile one-way trips with significant hills over half the route, I averaged about 235WH/mile. Your beetle would weigh several hundred #'s less so the wh/mile should be proportionally lower since wind drag isn't the main factor in this case. I used between 8 and 9 KwH on each of the drives.

FWIW if you wanted to increase your budget by a few thousand, and if you could benefit from regen on the rolling hills (instead of riding the brakes) you might look into some of the low voltage AC systems that have come out recently. $3-5K for 108V motor and controller, good for up to about 40HP. For AC, a good deal and would be ideal for your desired usage pattern. You could recoup some of the incremental cost selling your warp motor. 

Good luck.


----------



## tony3811 (Jul 30, 2010)

I guess it was premature for me to say 5k. I know it will be more. But here is the latest on the battery pricing that I've been able to get:

38 LiFe04 (100AH) = $5064 

10 Deka Gel (98AH) = $2611


Part of my thinking says go with the Gel because in 2 years when they are toasted I hope the battery prices will have come down and I can get something better. 

Is there a way for me to compute this data better? I mean in know they say similar Amp Hours but I've heard the gel wont use all of the available amps once it gets close to 50% discharge on the pack so you only use half of the batteries available energy. Is this right?

I just wish I had a way of comparing these options better. I think knowing what each of these packs would put out when installed would help me make my decision rather then relying on gut feelings not based in fact.


----------



## rillip3 (Jun 19, 2009)

I would avoid the gel batteries. My understanding is that they don't take to high amperage applications well, and you'll be pulling high amps over a short period of time. AGM or flooded would be better. With flooded you're looking at about 50% usage due to Puekert's effect. With AGM you can get about 80% out.


----------



## Guest (Jul 30, 2010)

You will have more usable energy with the lithium and they will last way longer. In the end they will be cheaper than the others and you will have a way lighter vehicle. I am building our 2nd VW Ghia and we will be using lithium. I plan on 160, 180 or 200 AH batteries for distance. I do not plan on a super hot rod but when done the vehicle will scoot along just fine. With lead and 96 volts it will do 85 mph. Acceleration is like a stock engine. The higher voltage that we want to use will push it along real nice. 

The Nissan Leaf will be in our driveway too. 

Pete 

Here is our first EV. http://greenev.zapto.org/electricvw


----------



## corbin (Apr 6, 2010)

Where are you at? I'm also in the Bay area (Los Gatos / Santa Cruz mountains) and I'm pretty much at the same stage in my '69 beetle conversion. 

I wouldn't mind having someone else local to work with and discuss ideas. Email me if you want.

corbin at (my domain)
http://www.corbinstreehouse.com


----------



## madderscience (Jun 28, 2008)

as for your concerns about comparing batteries, there is some science to it but unfortunately an awful lot depends on voodoo. Look Here:

http://www.diyelectriccar.com/forums/showthread.php?t=11709

for a good summary of the science part.

The voodoo is accounting for your stop and go, headwinds, the fact that the left rear tire is 5PSI low, cold or warm ambient temperatures, the grand piano lashed to the roof of the car, etc. All of these things can cause you to burn a little more energy than usual.

So a basic rule of thumb I have decided on (which you are already meeting it seems) is to try and build for a maximum range that is about double what you will typically want to drive. You said you have a 16 mile commute, and want 40 miles range so you are good there.

Once you know your maximum range, you need to know the car's efficiency or watt hours per mile to get to battery size. If other similar cars have been built, get the numbers from their owners; otherwise do some research on similar cars in similar usage patterns and make your best conservative guess. Then just multiply range (miles) by efficiency (wh/mile) to get battery pack usable capacity. If you want 40 miles and get 200WH/mile, you will need a 8,000 WH (or 8KwH) usable capacity battery pack. Finally, scale the usable capacity based on peukert and DOD for your chosen battery. For lead acid, it basically works out to double the number (16KwH). For lithium, multiply by about 1.3.

The flooded lead battery pack option I threw out in my first post is nominally 120V at 150AH. This is 18KwH nominal capacity. Accounting for DOD and Peukert would leave you about half of that, or 9KwH usable capacity, which at 200WH/mile would get you 45 miles.

A 100AH, 120V lithium pack would have 12KWH nominal capacity. However due to their better chemistry, you can still get about the same 9KwH usable capacity out of them despite their smaller nominal capacity. Your WH/mile would be lower too since the whole pack would weigh half what the equivalent lead pack does, so you might be able to get 50 miles out of the car with this battery.


----------

