Adventure EV

Fuel tanks.

by on Feb.12, 2010, under Batteries, EV Land Rover

Just before I had to leave the southwestern Rockies for California’s warmer wetter climes a set of large crates arrived containing my fuel tanks, Lithium Iron Phosphate (LiFePO4) cells manufactured by Thunder Sky Energy Group in China.

Crates of LiFePO4 cells

In total, the battery system is capable of containing about 33 kWh of energy which should be able to give my Land Rover an approximate range of between 55 and 75 miles, when conservatively discharged to 80% capacity.  Or with the amount of electricity I’m currently using, enough electricity storage to power my house for two days.

Each cell is 3.2 volts-nominal and stores 160Ah of energy.  I’ve got 64 of them.  The calculation to determine how much energy a group of cells can store is:

Total Capacity = cell voltage x cell capacity x number of cells = 3.2V x 160Ah x 64 = 32,768 watt-hours.

And the calculation of how much range achievable is:

Range = pack capacity / vehicle watt-hours per mile = 32,768 /  500 = 65.536 miles

This last range calculation is tricky and highly variable.  It’s only the roughest estimate based on the average efficiency of my vehicle based off of parameters like weight, aerodynamic drag, average speed, rolling resistance, and drivetrain drag.  Driving slower will decrease the watt-hr/mile usage, while driving faster will increase it.

Based off of the real-world experiences of others, however, an EV conversion will range between 200 and 500 watt-hrs/mile, the former figure being with a conversion of something light, small, and aerodynamically efficient like a Geo Metro, the latter being a heavier, bulkier conversion of… say, a 40 year old Land Rover.

Each crate contains 16 cells.

Crate of 16 cells

Each cell is about the size of a large, hardbacked, Tolstoy novel and weighs about 5.6kg (12.32 lbs) for a total pack weight of just over 350 kgs (or about 760 lbs).  That’s about the same amount I took out of the Land Rover in ICE components.

Cell detail

The cells come grouped in sets of four which just about matches the size of a conventional 12v Lead-Acid car battery, but you can specify alternate groupings if desired.  You can see the aluminum end-plates and strapping hardware below.  It’s used to prevent the cells from swelling when taking a charge.  Swelling increases internal resistance, which reduces power output.  This behavior is really only prevalent in prismatic lithium cells.  The trade-off is a reduced cost and a cell that is capable of storing a large amount of energy.  Having to strap the cells together becomes a minor inconvenience.

Grouped cells

In designing my battery boxes, I added a bit of space for cell end-plates, but I had no idea that the stock hardware from Thunder Sky would be as robust and thick as it is.  Unfortunately, these cell blocks don’t fit my boxes,  but all is not lost.  I will probably discard the provided plates and use the structure of the battery box itself to accomplish the same task.

Also included in the shipment was a box full of harware for hooking up the electrical side of things.  Here we have aluminum bolts and laminated, copper interconnect bars wrapped with heat shrink tubing.  The copper bars are used to connect the individual cells together, while larger and longer runs of 2/0-sized welding cable will connected the battery boxes together and to the motor controller and charger.

Included hardware

The next task is installing all these cells in the battery boxes, mounting them to the Land Rover’s frame, and wiring it all up.  Oh, and sort out some kind of battery management/monitoring system.  More on that later… when I’ve sorted it.

None of this will happen until the spring, however, as other work demands attention.

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The Good, The Bad, and the Ugly

by on Dec.24, 2009, under Batteries, EV Land Rover, The Knowledge

Sorry for the gap in posts.  It’s been a very hectic couple of weeks!

Funding an electric vehicle conversion…  You’re not entirely alone here, depending on where you are.  It’s odd that there’s no real support for alternative fuel vehicle conversions at the Federal level, considering the country’s “green awareness” climate, but individual states, and sometimes even individual counties offer tax incentives for alternative fuel vehicles.  That’s good news.

Sometimes the programs are quite generous, but due to ongoing difficulties with state budgets most are being cut back quite a bit for 2010 and beyond.  That’s bad.

In order to take full advantage of one of these programs I need to have my Land Rover certified as an electric vehicle and registered before the end of 2009.  I’m also heading back to the east coast for the upcoming holidays.  It doesn’t leave me a lot of time to get stuff done.  That’s ugly.

Ahh, if that were all…

In order to ensure my shot at taking advantage of one of these programs, my Dad graciously booked a vehicle inspection in Broomfield, CO, just outside Boulder, CO, for December 17.  Broomfield is 350 miles away.  Ohhh, that’s bad.

And my batteries have been delayed from China.  That’s really ugly.

In fact, they will not get to me by the end of 2009, and that’s just sad.  But it is what it is.

Here’s the good.  Christmas came a bit early this year:

Of course those four, deep-cycle, lead-acid batteries weren’t just for testing the controller!  They were, in fact, part of my backup plan.  That’s my Dad driving, and me on the wobble-cam.  Sorry about that.  My budget on this one is all going into the build…

First impressions:  Torque from zero rpm is a very good thing.  The Soliton-1 motor controller is amazingly quiet, there is no high pitched whining as the motor spins up, only the slight whirring of the two small cooling fans.  The motor is amazingly quiet.  In fact, pretty much the only sound you can hear in the video is the tires on snow.  A Prius in electric mode makes more noise.

Colorado doesn’t care whether the electric vehicle is finished.  They just care if it’s an electric vehicle, and that means no ICE.

Motor Bay

Temporary 48 volt lead-acid setup while waiting for the LiFePO4 cells to arrive. No ICE to be found. High tech broom handle acts as bonnet stay.

So with a top speed of 20 mph and range of… who-knows-but-I-don’t-want-to-test-it, we loaded the Land Rover onto the back of a U-Haul auto-transport attached to my other Land Rover (a Range Rover) and towed the rig up to the Broomfield Technical Center.

Loaded Up

I was actually surprised how well the Range Rover handled the extra weight.  All told, it was moving about 10,000 pounds over mountain passes at 5000-8500ft ASL, and even then we managed to maintain 65-70mph most of the way and average 11.5 mpg with nary a wiggle from the rear.  How the H2 Hummer, which doesn’t weigh 10,000 pounds, achieves less than 10 mpg is beyond me.

New and Old

Don't worry about the Range Rover's sagging rear. Once on the move, the air suspension raises to keep everything level. The Series Land Rover has no idea what that means.

This is definitely one arena where ICE will win out over EV.  It’s not that electric motors can’t provide enough power (diesel locomotives, after all, run electric traction motors,) it’s that the amount of energy required to move 10,000 pounds at highway speeds for 350 miles is just immense…more than 15 times the amount of energy I can store in a single charge of my battery-pack-to-be.

Testing

So we made it to our appointment with the state tech inspection station (apparently my camera did not, as witnessed by the terrible phone pic), and the truck passed with flying colors!  I didn’t even have to drive it off the trailer, which slightly disappointed me, but who was I to argue…  They just checked the VIN number, popped the bonnet to ensure there was no ICE in there, and issued a document indicating that a new title with change of fuel status to electric be issued.  The guy at the inspection center was gracious, very helpful and mentioned that there were quite a few electric conversions in the Boulder, CO area, but no Land Rover’s that he’d seen.

Pass Screen

Screen at the testing center reads: "This vehicle has been converted to dedicated electric power."

The next day we applied for a new title and registered the car.  So it’s all legal now.  And it’s technically an electric car.  So I’m claiming a bit of success regarding the challenge of converting the Land Rover to electric power by the end of 2009.

It’s not done, of course.  I still have quite a bit to do to fulfill my original design goals.  Pretty much all the fabrication is complete, save for some small bits here and there.  But I still have to load in the lithium cells, and obviously that can’t and won’t happen until 2010.  I’m actually writing this stuck in an airport on my way back to the east coast while a blizzard rages.  I won’t be back to the project until next year.

Temp Setup

Chances are that I won’t really be able to complete the project until the spring.  The last few weeks have been difficult, a true learning experience, and ultimately satisfyingly fun, but I need to get back to working on some projects that pay the bills.

This is a good thing.  The weather will be warmer, and I’ll have a battery management system (BMS) design in place.  I can finish painting.  And, I can work out why my clutch only disengages 90% of the way, I suspect my motor adapter spacer is too thick by about a 1/16th to a ¼ of an inch.

But don’t worry, I’ll try and get some pictures of those lithium cells.  They should come in just as I get back in the new year.

So have a great Holidays, everyone.  Stay safe!

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Battery Box Update

by on Dec.15, 2009, under Battery Boxes, Controller, EV Land Rover, Fabrication, Heater

Did I already do a battery box update?

The one continuous thread throughout the conversion has been the fabrication of the battery boxes.  It seems these things take forever to build.  But it’s been cold… and I’m being whiny.  I must admit that they are pretty heavy duty, though.  Far more robust than they probably need to be, but probably beefy enough to handle off-road rigors, if necessary.  Like everything in this Land Rover, they’re built tough… very fitting.

Most people build a tray that the battery cells sit on, usually located somewhere in the engine bay, or more commonly, in the trunk.  I wanted to build sealed enclosures that sit completely under the vehicle, out of the passenger compartment.  Since I’m using lithium cells this shouldn’t be a problem.  Flooded lead-acid batteries, in comparison, vent hydrogen gas when they charge.  You wouldn’t want one of those in a sealed container…

There are four boxes in total, carrying 64 LiFePO4 battery cells.  Two sit on either side of the vehicle where the stock fuel tank locations were, just under the seats.  A larger rear box sits tucked up between the rear axle and rear frame crossmember.  The final box sits in the front of the engine bay.  All of it is made from 1/8″ mild steel in various forms; angle iron, square tube, strap, sheet.  Aluminum sheet is used to fill in the gaps and cut down on weight, but even with that saving measure I’m guessing all the boxes will add at least 150 pounds to the rig.  Not great, but they’ll last forever and be able to take some abuse.

Here’s one of the side box frames being held in position under the chassis by a Harbor Freight transmission jack.  Once full with batteries the jack will be the only way to get the boxes in place (the rear box will weigh about 260 pounds), a very worthwhile investment!

Side FrameThe rear box sits between the rear road springs and hangs from the rear crossmember.  Another piece of angle iron stretching between the frame rails anchors the front mount.  There’s a nice, empty space under the short-wheelbase Rover.  I had previous modified a Jeep fuel tank to fit back there.  Now the space is home to a different fuel.

Rear Frame

Crossmember DetailThe Rover has an unusually short rear overhang.  Great for off-roading.  I probably lose a couple of degrees with the rear box hanging down, but it shouldn’t pose a problem.  All in all, it’s quite an elegant fit.

Rear Clearance Since the top of the boxes are angle iron to provide strength and a lip to seal the top lid against, they pose an obstruction for the cells, so notches were strategically cut to allow groups of strapped cells access.  Not having the cells made this hard.  I just have to trust that the dimensions will allow for the clearance.

The final frames were painted with POR-15, and aluminum sides were cut to size.

Frames OutsideOK, granted the thin aluminum sheet isn’t exactly the toughest stuff in the world… But finally, something that cuts like butter!  And here’s the tool that does it.  Harbor Freight electric metal shears that make quick work of the box walls.  Say what you will about the quality of Harbor Freight stuff, but it’s cheap, and gets the job done for the few times people like me need something done.  And having the right tool for the job makes all the difference!

Shears

Once the sides are cut, they’re riveted to the frames.  A combination of the paint and sealing caulk ensures no galvanic reaction between the steel and aluminum, and helps seal the box from the elements.  Here’s Dad helping out with the riveting.

Dad Helping

A very nearly finished rear box.  I suppose I could leave it this way, but the plan is to spray self-etching primer on everything and coat with a semi-gloss black.  However, it’s been too cold to do any of spray painting.  All in good time.

Rear BoxI’ve sized the boxes to be slightly larger than the cells so that I can place some insulating foam around the perimeter.  This will help against shock and increase the insulation factor for the cold season.

The LiFePO4 cells should be fine just sitting in the cold, but they don’t like being charged in sub-zero weather.  To help performance in colder months, heaters are employed.  The bottom of each box gets two layers of aluminum.  One layer acts as the exterior wall.  A layer of foam (temperature tolerant Ionomer Foam from McMaster-Carr)  sits on that, and then thin battery heater plates from KTA Services, Inc sit on the foam.  These heaters are rated at 35w each and run off of 120VAC.  The idea is that these heaters will connect directly to wall power when the EV is charging in the winter.  As the cells discharge during normal driving, they should create enough internal heat to suffice without the heater pads active.  The second layer of aluminum sits on top of the battery pads, not only to protect them, but also to help spread the heat under the cells.

Heater

The hardest box to build was the front box.  I had originally designed the rear box to contain three rows of eight cells, for a total of 24 cells, but the rear differential pumpkin got in the way.  One of the rows of eight had to go, and in its place I got a compromised sideways row of three.  I had to find a place for five more cells.

The Rover does have a bunch of hiding places for more battery capacity, but rather than try and mount a fifth battery box, I decided to modify the front box.  It turns out space is becoming a premium if I want to keep everything moderately contained and relatively simple.

Instead of only needing to house 16 cells, the front box was widened to contain 18, and a small side box was welded to the back providing the space for the final three cells.  It’s weird, but it works as well as it can without the actual cells on hand.  I really hope I’ve left enough wiggle room.

The front battery box will have a clear acrylic lid for extra “bling-factor.”

Here’s the basis for the front box.

Simple Front FrameThe frame bolts directly into the frame rails.  Another set of brackets was fabricated to carry the bigger electronic items, the charger and motor controller.  The charger is another piece I don’t actually have yet, so I’m hoping the dimensions I found online are correct.

TrayThe charger sits a few inches above the motor, behind the battery box, and the controller sits a few inches above the charger.  The front of the “components” frame is bolted to the back of the battery frame so that it can be removed separately if needed.  The rear of the frame bolts directly to the vehicle’s bulkhead/firewall.

Once everything is tight the whole assembly ain’t goin’ nowhere.  It’s extremely solid!

Full Frames

Again, gotta love that access!  The Rover makes this conversion so easy in some ways.

Hopefully, all the miscellaneous electronics (fuses, contactor, shunt, relays, etc.) will sit behind the controller, up against the bulkhead.

Wait, I have the controller!  What’s that look like in place?

Electrics FinishedWhat are four, deep-cycle, flooded lead-acid batteries doing in the battery box?

Controller UpdateWhy, helping test out the motor controller, of course…  That’s an ethernet cable attached to the Soliton-1, with the controller’s configuration page on my netbook…

I can’t end the story there… can I?

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