[EVDL] Electric Sun Buggy

On 30 Aug 2007 at 19:27, ZillaVIlla wrote:

> if they cost $13,000 to build now (we make
> them from "Scratch"), where does it become cost effective to go electric
> (initial investment VS. operating expense)?

I'm lousy at this stuff, but let me do some musing.

For one thing, it's tough for EV components to match the cost of ICE
components. They just not produced in large enough volumes. But I'm going
to leave that for others to ponder and consider only the costs of operation.

If you were running your cars for an hour a day each, it'd be easier. But
running 8 hours a day flat out means that you have to have at least 8 hours'
worth of battery on hand - let's say that's 4 packs per car, since your
customers take them out for 2 hours at a pop - all charged and ready to go
every morning. (I'll come back to this "2 hours" issue in a moment.)

I'd guess that means about $8,000+ worth of batteries per car. Actually,
I'm thinking about a dozen AGMs per pack here, but that may not be enough.
With about one-third the vehicle weight in lead, your range would be
typically 30-40 miles on the road in easy driving - about an hour at 40 mph
with some stops here and there. So I'm a little worried. But for the sake
of argument, let's say for now that 12 Optima Yellow Tops would get you
through your 2 hours. (If not the numbers that follow will have to be
adjusted - upward.)

First let's assume you charge all your batteries overnight, and you swap out
batteries for every new customer. This means wrestling 450-500 lb of
batteries out and in every time the car comes in. Hopeless? No, not at
all! The Formula Lightning racers did this kind of quick change regularly.
Of course their cars were designed for extremely quick battery changes, and
yours would have to be too. But it can be done. You might want to hire
some college football players to do the heavy lifting. ;-)

The alternative is to have one battery pack per car, and a charger that can
dump in a near-full charge (20%SOC to 80%SOC) in, say, an hour. How tough
would this be? What would you need?

IIRC, an Optima YT yields about 45ah at real-world EV currents. Let's
assume you'd use only 60% of that (20% SOC to 80% SOC) during the day.
(Whether < 4kWh is enough to keep your customers humming for their full 2
hours on the sand will be left as an exercise for the reader.)

Figuring 85% charger efficiency, you'd be shoving in about 4.5kWh per cycle
(more when you topped 'em off at night). To do this in an hour would
require one 4.5 (make it 5kW for safety) charger per car, and an electrical
service capable of supporting all those chargers.

At 1 hour charging for 2 hours of use, you'd need about 50% more vehicles
than you now have (right?), so you can have one down charging while two are
out running. Now we're up to 75 cars. Say that the most you'd be charging
at one time would be 25; you'd need a ~120kW service just for the cars.
That's 2.5 times the typical home service's capacity, but probably not a
problem for a commercial situation.

Multiply this by the number of cars you typically have running in a day and
then by the number of runs each makes per day to figure your daily kWh
usage. Add another 1.5kWh or so for the overnight finish charge that you
couldn't do when fast-charging for the next customer, then multiply by your
electric rate. If a car ran 4 times per day and you pay 14 cents per kWh,
your cost per car per day is ((4.5 * 4) + 1.5) * 0.14 = about $2.75 per car
per day.

If you were swapping packs, you'd actually have more fully charged batteries
but ironically you'd use more energy (there's more loss in the last 20% of
the charge). For a car that ran 4 times per day, you'd probably use 6kWh *
4 * 0.14 or about $3.35.

Whether you swap batteries or charge them onboard, you're going to be
replacing batteries every 300 to 500 cycles - one cycle would be a 2-hour
trip out. It might be less, with ambient temps in the 115 degree F range,
but for the moment let's go with the above figures.

If they're running 4 cycles a day, that's battery replacement every 75 to
125 days, with a cost for batteries alone (exclusive of labor) of about $4
to $7 per charge just for battery amortization - or (again assuming your 4
runs per day) $16 - $28 per day. So your cost for energy and battery
amortization is about $19 to $31 per day, exclusive of labor costs.

Check my math. Assuming I got it right, how does that compare with your
fuel costs now? Don't forget that you could dispense with such maintenance
items as oil changes and exhaust system repairs. (But you'd probably have
motor and controller failures from time to time.)

One other thought. Cost questions aside, I'll bet that part of the thrill
of these rides is the roar of the engine as they're gunning it up those
hills. Consider what some people say about electric drag racing - exciting
to watch, but something's missing. That something is the racket! We're
trained almost from birth to assocate noise with excitement and power - just
listen to a little kid's motor noises as he races up and down the sidewalk
on his toy ride-'em car or tricycle. What this would do to your business I
don't know, but you might want to give it some thought.

All the figures I've cited here are wild guesses. The real world costs
could be far different. In particular, if the example above (12 Optima
Yellow Tops per car) isn't enough, costs could skyrocket.

To be honest, experience suggests that with fuel and material costs are they
are right now, saving money with an EV requires very specific and carefully
controlled circumstances. I'm not sure your situation complies with those
circumstances. In fact, to make EVs cheaper than ICEs almost requires the
cheapest cost-per-mile batteries available, golf car batteries - and I don't
think those would do for you at all. I figured several years ago that AGM
batteries (which you'd probably need) cost about 7 times as much per mile as
golf car batteries (that's 600% more). And batteries will probably be your
largest recurring cost.

I'm going to risk raising others' ire and say that I'm not sure your
application lends itself well to EVs. Low-speed, short-mission, stop and go
routes - the kind that tear up automatic transmissions, wear out brakes, and
clog ICEs with carbon and sludge - are ideal for EVs. But that doesn't
sound much like your cars. It sounds like they get ridden hard all day long
and then are put up wet.

You might still want to go EV. There are many reasons people and
organizations (many of them on this list) use EVs in situations for which
they're not (currently) too naturally suited - because they believe that
they have environmental benefits, because they're different and cool,
because they project a "green" image. If that's what you're looking for,
maybe you >should< consider EVs.

But if you're looking for cost savings - that's a tough one. If that's your
objective, I suggest you sit tight. If I'm reading your situation right,
EVs are unlikely to save you money any time soon.

But I could be wrong! You could always build a couple and see how they work
out.

David Roden
EVDL Administrator
http://www.evdl.org/


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ZillaVIlla wrote:
> I currently work for a dune buggy adventure company in Las Vegas
> http://www.sunbuggyfunrentals.com
> how this could be done better with an electric power train?

Sounds like a fun business, and a challenging project for an EV!

EVs and ICEs are good at different things. So (as others have pointed
out), I don't think you would have much success just building an
electric version of your present vehicles. I would contrast the two like
this:

ICE vehicles Electric vehicles
------------ -----------------
fast slow
noisy quiet
dirty clean
high maintenance low maintenance
cheaper to buy cheaper to run

So, I would approach it from a different angle. Imagine an electric
vehicle that could be used on the sand dunes and still be a "fun" ride.

For instance, maybe it's a larger "fishbowl" type of vehicle, with
superb visibility in all directions, but air conditioned inside, so you
stay nice and cool and clean (no sand in your shorts)! Maybe it's a
tracked vehicle, much slower but it can float over the sand with hardly
any disturbance (the slow speed means low power consumption, so electric
becomes feasible). Dead silent in operation.

Or, I've seen a recumbent bicycle that used gigantic high-flotation
tires. The builder claimed it had such high flotation that it was easy
to ride over sand, snow, mud, and even water. If it could work as a
human pedalled vehicle, it could be electrified with a pretty small
motor and battery pack, to still be light and nimble.

Or, I've seen some really "mad" vehicles that could be great fun in your
situation. Imagine a huge beach ball, 10 feet or more in diameter, made
of clear plastic. It has an axle through the center, and a seat hangs
from this axle inside the ball. A motor on the seat rotates the axle;
because of the weight of the seat, motor, and driver, the outside ball
rotates, and it rolls forward over almost any terrain. The axle was
hollow, and the ICE sucked air in one end, pressurized the balloon to
hold it up, and blew the excess air and exhaust out the other end. It
would be highly desirable to make such a thing electric, to eliminate
the exhaust fumes of the original ICE-powered version.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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--- ZillaVIlla <[email protected]> wrote:

top speed is
> about 50 MPH but they rarely see over 35 MPH

Definately do-able with electric but you have to limit
the tours to one hour so someone doesn't run out of
charge. If the have flat tops add a couple of solar
panels and if they do run out of charge they could set
for a few hours and get back. better than running out
of gas in the hot sun.


we have a company here in san diego that rents slow
electric catamerans for the bay. they use 24v agms.
but have room for more I always wanted to rent one and
push the voltave to 72 and have some fun. electric is
doable but you need 4 battery packs for each vehicle
or a large charging current so as to have full packs
available for each rental

I have a place in the desert and use quads all the
time but unlike my kids i go slow and look at stuff.
hat3e the noise and always wanted an electric that was
nice and quite so it didn't scare all the wildlife


>
> and of course they run on unleaded fuel. we have
> about 50 of these and are
> building more.
>
> I've rolled around in my head (Longtime lurker here)
> how this could be done
> better with an electric power train. No oil or Gas,
> less moving parts, easy
> to speed or torque limit independently. Perhaps the
> battery pack could be
> changed at the end of each 2 hour tour and the old
> pack plugged into a
> charger for the next trip? In the current
> configuration the Buggies weigh
> about 800 Lbs. I figure you'd save weight in the
> engine to motor conversion
> and then gain it back with your gasoline to battery
> conversion. Has anyone
> any examples of how this has been done before?
> These things bounce LOTS so
> I don't know if it'd be better to go with a certain
> type of battery over
> another. Expect that each buggy would run 4 times a
> day for 2 hours each
> time, every day 365 days a year. if they cost
> $13,000 to build now (we make
> them from "Scratch"), where does it become cost
> effective to go electric
> (initial investment VS. operating expense)?
>
> Just wondering if anyone here can help me by
> referring to past solutions
> with similar operating conditions.
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ZillaVIlla wrote:

> I currently work for a dune buggy adventure company in Las
> Vegas (gets up to 115 degrees here regularly during the summer)
> http://www.sunbuggyfunrentals.com
> Our Buggies are powered by 670cc Air and Oil Cooled V Twin
> motors and mostly run 2 hour long adventures on varied terrain
> uphill, downhill, sand, hard pack,rocks, and gravel. In their
> current configuration the top speed is about 50 MPH but they
> rarely see over 35 MPH
>
> we have about 50 of these and are building more.

How many do you add to the fleet each year?

I think that replacing your present fleet would be a decent enough
volume to perhaps allow you to get better pricing on components or even
access to parts individual hobbiests can only dream about, but
realistically you might be looking at only building perhaps 10 vehicles
a year on an ongoing basis.

> Perhaps the battery pack could be changed at the end of each
> 2 hour tour and the old pack plugged into a charger for the
> next trip?

How much time is available between trips? The pictures on your site
suggest the buggies are carried to/from the tour start on a car-carrier
type arrangement and it might be a pain to add an extra unload/re-load
step at your base if the buggies aren't presently unloaded between trips
anyway.

How much time do the buggies spend on the trailer; might it make sense
to charge them while on the trailer?

> In the current configuration the Buggies weigh about 800 Lbs.
> I figure you'd save weight in the engine to motor conversion
> and then gain it back with your gasoline to battery conversion.

What does the present engine, CVT, and chain drive weigh? How much fuel
does the tank hold?

There is no doubt an electric buggy would end up weighing a few hundred
pounds more, but the basic buggy is so light that the
battery-to-curb-weight ratio should still be much better than most any
on-road EV. Performance should still be at least equal to the ICE
despite the weight, and the EV could seem more powerful than the ICE by
virtue of having better low end torque and smoother torque application
when starting.

> These things bounce LOTS so I don't know if it'd be better to
> go with a certain type of battery over another.

It would bias me toward spiral wound AGMs such as Optimas, if going with
lead acid. How often do your customers flip the buggies? Ultimately
that would be the deciding factor between using floodies of any sort or
not.

> Expect that each buggy would run 4 times a day for 2 hours each
> time, every day 365 days a year.

How much idle time between runs? How much time spent in transit?

> if they cost $13,000 to build now (we make them from "Scratch"),
> where does it become cost effective to go electric
> (initial investment VS. operating expense)?

This is impossible to anwser without any knowledge of where your present
costs are. How much of the $13k is associated with the ICE bits and
present drivetrain? What are typical maintenance costs, and what are
the maintenance items? I notice your ICE buggies use belt-type CVTs and
it appears they use an exposed chain final drive. Belts tend to be high
wear items and aren't particularly cheap; how about the chain and
sprocket in the sandy environment?

Here's my thoughts. You might have enough volume and be an iteresting
enough application to gain access to the Zebra NaNiCl battery; MES-DEA
focuses on OEMs, and you just might squeak in if you get the sales pitch
right. The advantage here is that the Zebra battery is a pre-packaged
deal; you just bolt in a 450lb steel box containing the battery and all
its management systems. The typical Z5C battery configuration is a
~278V 17.8kWh pack, which would lend itself well to pairing with an AC
drive, perhaps something like the 12kW continuous MES 150-100 motor (see
Victor's MetricMind site) and a suitable controller? Supposedly the
Zebra is available in configurations down to 24V, so if you were able to
get access to a Zebra configured to be in the 80V range you could
consider using a lower cost 72V sep-ex drive or even a 72-80V AC drive.

Hi Performance Golf Cars <http://hiperformancegolfcars.com/> has a 48V
AC system for golf cart applications which delivers 80ft-lbs from
0-750RPM and 18HP peak (2000-2500RPM) while winding out to 6500RPM+
(specs here <http://hiperformancegolfcars.com/content/view/3/12/>). Not
on their website, but also available is a 72V version. Retail for a
650A 48V AC drive conversion kit appears to be $2500:
<http://aevgolfcars.com/cart/product.php?id=6282> (notice that the motor
picture reveals that the motor is intended to bolt up to a standard
GC/NEV diff to provide the DE bearing). The kit would include the motor
and matching programmed Curtis AC controller and may contains a few
other bits and pieces. As a "manufacturer", I expect you could buy
direct from Hi Performance at a lower price.

The suggestion to investigate the Zebra battery is that it operates at
270C internally, and so is completely unbothered by your 115F ambient
while just about any other battery will be. Also, unlike just about any
other advanced battery I can think of, it comes packaged with any BMS
and termal management systems built-in. It comes with a 1yr warranty
and a 5yr warranty is available.

With high floatation tires, and such a light vehicle, I suspect the
energy consumption won't be all that bad. At 200Wh/mi and 40mi/tour,
this is 8kWh. With the 3.3kW charger used with the Zebra battery, you
could get about 6kWh back into the battery in 2hrs of charging. This
means that if you swapped batteries (or just run the EV every other
tour), you could have the battery charged enough before the next tour
that it would make it through the day without getting below 50%SOC and
would then fully charge overnight ready to start the next day.

Regen with the sep-ex or AC systems might well reduce the energy
consuption noticably (and should save wear on the brakes since your
present CVT drivetrain isn't going to allow much of any engine braking).

My suggestion would be to do as others have suggested and make a
prototype vehicle first to see if the goal is attainable. A 72V lead
acid system would need about 115Ah of usable capacity to deliver the
WAGed 8kWh/trip. Over a 2hr tour, this is an average discharge rate of
just under 60A, so not bad at all. You could pretty much do a
proof-of-concept with a 72V set of T105s (unfortunately about 780lbs)

A 48V golf cart probably wouldn't be able to make the full trip, but if
you retrofitted it with the 48V 650A AC drive and a high-speed gear set
for the diff (about 6:1 seems to be a "high speed" gears) you could get
an idea of whether or not it would give the sort of performance you
require, even if you had to limit the test run to 1hr or so to avoid
running out of juice. If you wanted to lighten the car more, run a set
of 12V AGMs or floodies and decrese your test run duration accordingly.

I'd probably start with a used NEV as the initial prototype. Say a used
GEM 2-seater. The 48 or 72V AC motor should bolt right up and perk up
the performance considerably. The transaxle is already geared to allow
25mph, so with the higher speed AC motor it may be possible to avoid the
expense of installing higher speed gears to allow a 35-40mph top end.
The IRS diff and front end disc brakes could be readily transplanted to
the rear of one of your chassis afterward if the initial performance
test result is good.

If the Zebra doesn't require horizontal mounting (I don't see why it
should, but who knows), I'd stick the diff and axles from a typical NEV
into one of your stock chassis, with a 72V AC motor bolted to it to give
an IRS rear end, and bolt the Zebra battery as low as possible on the
back of the roll bar hoop (about where the ICE is presently). This
might make the front too light, so you might need longer trailing arms
in the rear to shift the weight a bit further forward of the rear
wheels, or you might want to customise the chassis to shift the
passenger weight more onto the front wheels, or to allow mounting the
battery further forward (on the floor just in front of the seats
perhaps, or even just on the passenger side of the roll cage).

The NEV IRS diff arrangement would yield an IRS rear (it appears that
your present buggies may have a plain chain-driven straight axle?) so
that the CVT and its belt are eliminated as is the exposed chain final.
The AC motor and transaxle are now sealed and should improve vehicle
reliability in the sandy environment.

A prototype EV buggy would be essential to get feedback from your
customers as to whether or not they would want to drive one instead of
the ICE (sound, etc.). It may well be that the silence of the EV isn't
an issue until all of the buggies on a tour are electric, so the main
factor at least initially will be if the EV feels at least as peppy as
the ICE.

Cheers,

Roger.

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