Adventure EV

Fabrication

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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Back To Our Regularly Scheduled Programming

by on Dec.01, 2009, under EV Land Rover, Fabrication, Motor Bracket

I hope everyone had a great Thanksgiving!  I know I did.  No snow this year, but it’s getting cold around here nonetheless.  It makes working outside less than enjoyable.  We’re projected for a high of 28F on Thursday… so yay.  Well, I better get a lot done on Wednesday.

Starting the post out with a picture

It seems like it has been awhile since I last updated this blog with actual project material, but rest assured I’ve been toiling away.

One of the tricky bits has always been the connecting of the motor to the Land Rover’s transmission.  In some cases electric motors can be strong enough, have enough torque, to power the EV through a direct-drive link to the differential.  With my project, I decided I wanted to retain the transmission for a few reasons.

For one, I wanted to retain the full capabilities of the Land Rover.  That meant retaining the four-wheel drive system.  Sure, it’s not the most efficient way to go, but keeping the Rover’s full off-road capability was one of my design mandates, and the easiest way to accomplish this was to utilize the existing transmission.

Secondly, the transmission allows me to change gear ratios in order to improve performance and efficiency.  The Land Rover isn’t the lightest conversion, so being able to downshift to climb a steep hill could help.  My projections indicate that I’ll be able to do most, if not all, of my driving in third gear up to 60mph.  Past 60mph I’ll need to grab fourth.  We’ll see if I have enough torque to start off comfortably in third.

Electric motors like to spin, they’re not happy poking around, so while I may have enough torque and power to single gear most of my driving, it may not be the most efficient at slower speeds and higher loads.  Again, the gearbox gives me flexibility.

Thirdly, the transmission’s clutch becomes a safety device.  In the event of a motor or controller failure which might result in the equivalent of a full-throttle situation I can easily disconnect the drive through the clutch.  Let’s hope this doesn’t happen.

Lastly, it’s just easier.  Connecting to an existing transmission is a common conversion technique, so many components already exist to facilitate this… like my adapter plate.

Motor with adapter plate.  Flywheel and clutch mounted.

I once considered going with a direct drive AC system designed to haul electric buses around, but in the end I didn’t like the performance specs, and while that system (Azure Dynamics’ AC-55) was designed to connect directly to a rear differential via a driveshaft and yolk, I would have needed to engineer a way of connecting it to my transfer case if I wanted to retain four-wheel drive.

You may have heard that a good conversion means lightweight and no four-wheel drive, two rules I’m somewhat breaking.  Maybe more like bending.  The Land Rover, as we’ve discovered isn’t terribly heavy for what it is.  I’ll keep telling myself that.  And the four-wheel drive system is unlike most modern setups.

The Rover’s four-wheel drive system is actually very basic.  It’s a manually selectable, part time four-wheel drive system.  That means most of the time I’m only in rear-wheel drive, with the front driveshafts disconnected by freewheeling hubs.  While there are still an additional set of gears to run through in the transfer case, it also means that there are no frictional losses running the front driveshafts and wheels when I’m in two-wheel drive mode, as you would find in most modern drivetrains.  Not so bad.  During the occasions I would need four-wheel drive, I shove down a lever and I’m in locked four-wheel drive.  True, I still have to lug around the weight of the additional four-wheel drive components, but that’s the way it is…  otherwise I would have converted something like a Civic.

Anyway, back on target.  While waiting for some additional components needed to mount the motor to the transmission, I test fitted the motor temporarily.  I needed to solve how I was going to mount the motor to the chassis.  The motor and transmission, when coupled together, act as one big unit, but the transmission’s mounts really only serve the rear of the unit.  The motor needs to have a front mount.

Here’s what I saw with the unit bolted together:

Conundrum_v01

The yellow circles are the two existing motor mounts.  The red arrow is pointing out the only position I can wrap my motor mount bracket around.  Big difference in location.  That flat black plate is the bottom of the motor mount bracket.

Mounting the very back of the motor would have been perfect, but that’s not a very structural part, and it’s where all the motor cooling happens with a fan back there.  Further forward and I run into a band of metal that covers the internal brushes, that’s a no go.  Further still and I hit the electrical connection block, that’s out.  So just in front of the block it is, then.

I have two options here, try and build some kind of bracketry to connect everything up, but I don’t like the idea of being levered out that far away from the chassis mounts… or build new mounting points into the chassis.  The latter idea isn’t attractive as it would mean designing new brackets and welding them to the chassis, but it’s the idea that won out in the end.

First I built a template out of cardboard and determined where on the frame I wanted the new mounts to go.  I soon discovered that I wouldn’t be able to put the new brackets directly under the mounting band because of front driveshaft clearance, so the mounts go a few inches to the side.

Template

The brackets are made from 2″x3″ – 1/8″ rectangular steel stock.  Initially, I wondered if the 1/8″ wall material would be strong enough, but the existing chassis used 1/8″ material that supported 490 lbs of engine and accessories instead of the motor’s 200 lbs.  Weight won’t be the issue, hopefully the increased torque from the electric motor won’t be, either.

After tracing the arc designed to allow driveshaft clearance on the steel stock, I used an angle-grinder and cut-off wheel to transfer the shape.  Came out kind of nice,  a relief after shattering a half dozen cut-off wheels with previous tasks.  Cut-off wheels are tricky, a slight grab or cut to deeply at the wrong angle, and they just blow apart.

Cutout

A smaller bracket was fabricated for the other side.  Both brackets have open bottoms to prevent them from collecting and holding debris.  Once welded to the frame, they should be very strong.

I decided to keep the existing mounts, in case.  In case of what?  I don’t know… returning the vehicle back to stock?  Doesn’t seem likely, but the stock mounts aren’t in the way, so for now they stay.

Here’s the longer bracket next to the stock bracket… you can see the driveshaft below it.  While nowhere near the bracket now, when the front axle is under articulation off-road, the driveshaft would have hit the new bracket if it had no arch.

Detail

Here are the two brackets welded into place, and you can see the arch in the original mount, as well.

New Mounts In Place

I’ve painted the brackets with POR-15, which works brilliantly for this stuff.  I coated the frame with POR-15 awhile back and the paint is tenacious!  You can’t scrape it off with a screwdriver.  Only an angle-grinder has succeeded in removing POR-15 from the well prepped chassis.

Hopefully, by the end of tomorrow you should see the painted result with the motor in place and mounted!


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Battery Box Progress

by on Nov.18, 2009, under Batteries, Battery Boxes, EV Land Rover, Fabrication

I certainly expected to learn a lot embarking on this endeavor, and I have.  But something I didn’t really need to learn was that cutting 1.5″ x 15.” x 1/8″ angle iron with a 12″ mitre saw and an abrasive cut-off wheel… takes FOREVER!!!

So far I’ve cut pieces for three of the four battery boxes… 12 pieces for each box, two cuts for each piece, for 72 cuts altogether.  45 degree angles are the worst.  It’s like cutting thicker material.  The wheel just spins round and round… and round… and round before it cuts through.  I thought it would be like butter,  but it’s more like cutting through a can with a nail file, metal dust everywhere.

Cutting Angle Iron

And the abrasive cut-off wheel doesn’t cut cleanly at all.  Every time I complete a cut I have to de-burr, bevel, and smooth the edge with a 4″ angle grinder.  It just gets tedious.  Took a couple of days.  Word of advice, don’t do this without ear defenders and other normal safety gear.  You’ll go mental without the ear protection… and deaf.

I’ve heard of chop saws that use carbide-tipped metal blades that do cut metal like butter… and cleanly.  If I was doing it for a living I’d purchase one in a second, but they’re ex-pens-ive.  Another word of advice, get one of those!

But then it was on to welding, and for some reason welding is far more enjoyable.  I dunno, there’s something about melting two pieces together by brute force… and a lot of electricity… and sparks.

Welding

So after the past couple of days, the two frames below are the result of the fruits of my labor.  And what do you know, they actually kinda fit.  Tomorrow I complete the rear box frame… the big one.  That shouldn’t take long.  The welding is relatively quick and painless.  But I’ve run out of shielding gas… wish me luck trying to find some.

I purchased some thin gauge aluminum sheet which will act as the box walls.  That will be sealed in and riveted, not welded, and I can cut that stuff with electric metal shears.  Hopefully this time it will cut like butter.

Side Box Frames

I also pick up my motor spacer tomorrow…  hopefully.  It’s Taos.  Every time I call to see if it’s done it hasn’t been started.  Life moves at a different pace out here.  Luckily I’ve been preoccupied with the fabrication work, and I haven’t been pushing the machinist.

I dropped my flywheel off earlier in the week to have the starter teeth and a bit of the back side shaved off.  Maybe I can cut its weight by a third.  It’s a heavy bugger, so any weight savings would be nice.  It was a spur of the moment decision, so I failed to weigh it prior.  Oh well… heavy.  That’s how much it weighed.

Maybe I’ll never see my parts again…

For those looking for sources for parts and pieces:

1.5″ x 1.5″ x 1/8″ Hot Rolled Steel Angle – 80 ft @ $87.75 ($1.10 linear foot)

60 sq/ft .040″ 5052 Aluminum Sheet – $140.19 ($2.34 sq/ft)

Purchased at Metal Supermarkets in Albuquerque, NM.  You might find an outlet near you, or you can order online.

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