Tuesday, June 26, 2012

Six Month Checkup

Interim Instrument Panel
I've been driving my EV truck for about 6 months now and thought I'd give an update.  The short version is, it's great! The best part is driving by the gas station every day.  I put aside all interior finish work while working on the power train.  For the first few months I was driving around with a very austere interior including the minimalist instrument panel shown here.  It consisted of just the state or charge indicator and the multifunction motor display.  Without my dashboard and traditional instrument panel I had no odometer or speedometer.  However I quickly learned that, in second gear, my speed, in mph, was roughly equal to the rpm divide by 100.

BMS programming

Typical Discharge Data
I spent a lot of time during the first month or so of driving monitoring my charge and discharge cycles and adjusting my BMS settings.  Gotta give a big shout out to the technical support at Elithion, originally Robert Helvestine and now Steve Van Buskirk. They were very helpful in getting my BMS properly setup and programmed. I'm very pleased thus far with the performance of the Lithiumate BMS.  I can't over emphasize the importance of collecting and carefully evaluating charge and discharge data during the first month of driving.  I had to collected data from a number of charge and discharge cycles to determine exactly what was going on with my battery pack and to properly set all the parameters for my BMS.  Initially I thought that I had a bad cell that was not fully charging.  That can be seen in the figure to the left when green minimum voltage line drops off quickly at the end of the discharge cycle.  However, after monitoring the pack for many cycles I found out that the cell was fine.  The problem was my failure to do an initial balance of all the batteries before installing them.  I skipped this step assuming the BMS would do the balancing for me once the pack was setup.  This did happen but it took the BMS quite a few cycles to balance out the pack since they started well out of balance.  Another lesson learned.

Making it look nice

Dash Cap Installation
Once I got all the guts of the system working, I was able to turn my attention to fixing the interior.  I spent a good deal of time looking for solutions to repair the cracked vinyl dashboard.  This is a common problem with older dashboards.  I turns out there are a range of solutions from crack fillers on the cheap and ineffective end to professional removal and refurbishment on the beautiful and expensive end.  I opted for the middle ground--the dash cap.  A dash cap is a vacuum formed plastic piece designed to fit over the old cracked dashboard.  It's simply glued on top of the old dashboard with silicone adhesive.  Sounds simple, but is actually a lot of work to install properly.  The final product looks a lot better than the cracked dashboard but it's obvious that it's not the original dashboard--sorta like a Maaco paint job--much better than that an old oxidized finish, but nothing like first class paint job.
Integrated Instrument Panel
I really wanted the EV gauges integrated into the original instrument panel.  I don't like the look of gauges hanging off the bottom of the dashboard or mounted on top of the dash. I opened up the existing instrument cluster and mounted the state of charge meter in place of the now unused gas gauge, hooking the low battery warning to the old low fuel light.  I was able to put the Curtis multifunction display in the location of the tachometer, since I didn't have an analogue tach in the vehicle.  You can see the results on the left.  Finally I had the interior upholstery, door panels, and headliner replaced by a local shop.  They did a nice job, except for the speaker covers which I redid myself.  So far the only work I've subbed out on the job is the transmission rebuild and the interior upholstery.  I'm really pleased with the overall look of the vehicle now.
Completed Interior
The truck's big coming out party was at an EV car show last month on the Cal Poly Pomona campus.  My truck was there representing DIY EV conversion. The show included all the big boys, Nissan Leaf, Chevy Volt, and Tesla roadster.  The Reverend Gadget, of Revenge of the Electric Car fame, was also there representing the commercial EV conversion market.  You can see his EV speedster next to my truck.  That guy is definitely a character.  All in all the show was a lot of fun.

Driving Stats

My First Ever Car Show
One of the biggest lessons I've learned over the past six months is difference in energy use between conservative driving, normal driving, and unconservative  driving.  If I'm very careful about minimizing energy use I can get 70 miles out of a single charge of my battery pack. If I drive normally, not being particularly cautious about energy usage, I'll get about 55 miles out a charge.  If I just ignore my energy use and floor the vehicle at starts I'll get around 40 miles per charge.  I find when I have a limited energy supply and an ammeter constantly showing my energy use, it really leads to a lot of energy savings.  So, the stats
  • Range city driving: 60 miles
  • Max speed: 85 mph +
  • Acceleration 0 - 25 mph: ~3.5 sec
  • Acceleration 0 - 40 mph: ~ 9 sec
  • Charge time from empty: ~ 4 hrs using 240v source
This is now my regular commute vehicle.  I'm really enjoying it.  I still have several things left to do including: installing gas shocks to aid in lifting the bed, installing a cable disconnect for the main breaker, and making a sheet metal shield to protect the front battery pack from water during the few rainy days we have here in SoCal.  Those will be some nice summer jobs.

Friday, January 6, 2012

It's Running!

New motor mount with isolation dampers
I found enough time over the holidays to get all the essential things completed.  First I had to redo the motor mount to include rubber isolation dampers.  Thanks to those of you who pointed out I needed these.  Since I already had the motor mount welded without the dampers, it took a little ingenuity to figure out how to add the dampers without starting over from scratch. In the end I cut the original loose from the mounting brackets and installed a new structural element under the original with spacers to make room for the dampers.  Kinda of a Rube Goldberg solution, but it works.

Acrylic battery cover
I also built some acrylic covers for the batteries.  I'd never worked with plastics before and was worried about how hard this would be.  Fortunately for me my son recently learned some plastic skills and he helped me with the battery covers.  It really was a lot easier than I thought it would be.  The material is pretty pricey.  But it will keep fingers, tools, and other junk away from the battery terminals and still allow people to see them.  (I already like showing off my EV).  I still need to fab the acrylic cover for the main electrical board with motor controller, contactor, & DC/DC converter.  Just got the plastic for this cut today, so I should be able to get it done this weekend.

Bed reinstalled on its hinges
My friend, Chris, came over just before New Years and helped me reinstall the truck bed.  This too was easier than I had envisioned.  I welded some stiffeners at the ends the frame's c-channels and then tack welded hinges on the frame.  Chris and I then picked up the bed, set it place and aligned it properly.  The bed weights only about 220 pounds so two people can handle it easily.  I then tack welded the hinges to the bed.  We removed the bed, finished all the welds and reinstalled it.  Now I have a dump truck! 

Pin securing bed
At the suggestion of performance car enthusiast, I used a couple hood pins to secure the front of the bed.  I welded some tabs to the frame and the bed just in front of the wheel wells. The pins are accessible through the wheel wells so it's easy to lift the bed and display the battery packs and charger in the rear. (Please don't comment on the quality of the welds on the tabs for the pin.  I know I've still got a lot to learn about welding.)

I drove around the neighborhood and up and down some big hills to discharge the pack while Chris rode shotgun with the PC hooked up to the BMS.  After a couple of discharge cycles and some tweaking of the BMS parameters, I felt confident that the low voltage warning and the state-of-charge meter were both working properly.  So last week I started my EV commutes to work and back.  My commute is 20 miles round trip and I can make two trips on a single charge with about 10-15% charge left in the battery.  So I can get 40+ miles round trip.  This is a bit below my 50 mile design range, but it also included some highway driving.  Speaking of highway driving, I took it out on the freeway yesterday and today and no trouble keeping up with the average speed on the freeway.  My dash still isn't installed, so I don't know precisely how fast I was going, but I'm guessing about 65 mph and I had not maxed out the system.  I do a peak speed check when I get the dash and instrument panel reinstalled.

Still have a lot of stuff left on the todo list including:
  • Finishing battery and motor controller covers
  • Getting the interior reupolstered
  • Installing gas shocks to aid in lifting the bed
  • Putting a dash cap over the old cracked vinyl dash and reinstalling the dash
  • Installing the EV instruments in the instrument panel
  • Put a 220v outlet outside the garage so my wife can have her parking space in the garage back (I think I'll put this at the top of the list.)
A happy EV driver
I love driving it! It's so quiet.  The loudest noise is when the vacuum pump comes on.  Today guy in another Nissan D-21 followed me off the highway, pulled up next to me at the stop light and said,"Hey is that an electric vehicle?"  When I acknowledged it was he said "I new it.  I new it! I saw your batteries under the bed and knew it must be an electric vehicle."  We held up traffic at the stop light while he took photos on his smart phone.  That was even better than driving by the gas station on my way home.  I love my EV.  Now I need to think of a name for it.

Sunday, November 20, 2011

We Have Locomotion!

Pulling out of garage on electric power
Yahoo! It works!  After carefully charging the battery pack and working out a number of bugs in the setup of the battery management system (BMS), I decided it was time to take the truck out for a quick spin around the neighborhood.  What a thrill--nothing blew up, nothing caught fire, nothing shorted out.  I had a scare for a few moments when there was a weird whirring noise which didn't stop when the vehicle did, but I quickly realized it was the vacuum pump for the power brakes--it's working properly too, yeah!  

EV in the neighborhood
The drive was really short, just up the block and back twice.  I had no hood, no lights, no bed, laptop on the seat next to me logging data.  Didn't want to go too far.  It was cool and weird to be driving an making no noise except tire noise.  I think I'm going to like this. 

A happy EV driver
The purpose of this test drive, in addition to see if it worked at all, was to determine if my sensors on the drive side of the system were working.  I had some indication that my current pickup on the discharge side of the battery system wasn't working correctly.  I found out that was true, so now I've got to troubleshoot that.  Without this current pickup I can't tell how much of the charge I've used up--in other words I'd be driving around without a fuel gauge.  There's a long list of stuff that needs to get done before I can have a working EV, including:
  • Fixing the current pickup on the discharge side
  • Testing the controls on the discharge side to ensure the system shuts down when batteries are empty
  • Fixing the short in the heater
  • Making and installing battery and motor controller covers
  • Bleeding the brakes
  • Putting the dashboard back in and installing the new gauges
  • Putting the hood back on
  • Reinstalling the bed with a hinge and lift system
The end-of-academic-term crunch is here so I'm not sure if I can get all of this stuff done before the Christmas holiday.  Now that I think about it, working on my EV over the holidays would be a really nice present.

Saturday, November 12, 2011

Ooh, Ooh, It's Nearly Running

All wired up and no place to go
Battery pack with BMS chips installed
I spent a bunch of time over the last two weeks finishing up all the wiring for the battery packs, motor controller and the BMS (battery management system).  It's all up and running now.  I turned the whole system on--relays clicked, inverters hummed and nothing started burning--whew.  In spite of my careful checking and double checking of the wiring, I still was a bit worried when I flipped the breaker for my battery pack.

Brains of the BMS wired up
Theoretically, I could open the garage door, turn on the key and drive the truck out into the street today.  It would be slightly less than street legal since it currently has no hood, bed, tail lights, or license plates installed (minor little details).  However, that's not what's stopping from taking a quick emissions free spin around the block.  Before I actually power up the electric motor, I need to program the BMS, charge the batteries and make sure the system is working properly.  Failure to do this correctly could result in damaging the $8000 battery pack.  So I'm now working on programming the BMS. I was successful in getting the BMS powered up and connecting to it's computer via my laptop.  Unfortunately that was the limit of my success this last week.

We're engineers, let's be obtuse!

Snapshot of BMS data
I'm an engineer (civil engineer not electrical or mechanical) and I hate it when engineers write a technical document that can only be understood by the engineer who wrote it.  The BMS "manual" at the Elithion web site is just such a document.  I think most of the information I need is on this site, but it's not easy to find and when I find it it's often a very broad instruction that you can't complete without more information, or there's a ton of detailed information but no specific instructions on how to complete the task.  

Here's one of my favorite examples.  The setup page of the instruction manual tells you that "Many other parameters may be customized, but usually they are left to their default" with no further information on how to determine what you need to change and what you can leave at it's default setting.  One group of "other parameters" that you have to set are the information that the BMS uses to determine the state of charge, i.e. how full your batteries are at any point in time.  If you hunt around long enough you'll find two other pages, each tens of screens long, that I think may have the information I need to set these parameters.  It will take several hours of deciphering and a few phone calls to be sure.  

The Elithion BMS is definitely not a Mac.  It's a long way from plug-n-play and the company seems to like it that way. I've read a few posts by one of the Elithion engineers on several EV forums.  These guys are a lot like bad IT support folks.  They're way smarter than their customers about how their product works--duh--and they pride themselves in pointing out just how stupid their customers are--not a good way to get new customers.

Saturday, October 22, 2011

Wires, wires, everywhere

It's cabling not wiring
Rear battery pack cabling complete
Working with 2-0 cable
I finally finished running all the high voltage 2-0 cabling.  This included the jumpers on the battery packs, wiring from the battery packs to the motor controller, and wiring from the motor controller to the motor.  Working with 2-0 welding cable is a different kind of wiring than I'm used to.  You don't just snip this wire and screw it to a terminal.  Just cutting the wire, stripping it, and attaching a terminal is a significant task with special tools.  You also have to very carefully plan how you're going to run the cable.  This stuff doesn't bend like #12 house wiring.  The bends need to be gradual and you have to get the lengths just right.  It was especially tedious to run the two lines from the rear battery packs up to the front of the truck.  That task took a lot of creativity and 1/2 a day.  Most of the time was spent designing and fabricating the clamping points.  The cable needs to be secure without any points where it might rub on a sharp edge and wear through the insulation--that would be an unpleasant event.

Motor controller & DC-DC converter
Welcome to my hood
With the rear battery pack jumpers done and the main lines run to the front I tackled the under-the-hood wiring.  I wanted a breaker on the main line so it was easy to disconnect the power to work on the components.  This turned out to be a non-trivial exercise, again due to the difficulty of working with 2-0 cabling.  I was able to fabricate a bracket to hold the breaker out of 16 gauge sheet metal.  I found a nice plastic box to enclose the breaker at my local surplus store.  Not sure of it's original purpose, but it makes a decent electrical box. Again I had to make a bunch of short 2-0 cable jumpers to complete all the high voltage wiring under the hood.

With the high voltage cabling done, I moved on to running all the low voltage (12v) control wiring.  This was much easier, but still tedious.

Oh what a tangled web we weave
Legacy 12v wiring harness
I now have two major wiring tasks left.  The first is to hook the DC-DC converter up to the legacy 12 volt system for the truck.  The 12 volt system is powered off of the main (116 v) battery pack through the DC-DC converter.  This is not a simple as it sounds.  I'll need only about 20 percent of the old wiring system--just that portion that runs the lights, and accessories. All the wiring for the engine, ignition, alternator, and engine control module can be eliminated.  The difficulty is figuring what wires to get rid of and what to keep.  I've got all the wiring diagrams for the truck, but this is another tedious task.

The last wiring task is to hook up the battery management system (BMS).  This requires installing small circuit board on each battery cell and then wiring them into the BMS.  The circuit boards on the cells measure the voltage of each individual cell and can shunt the charge voltage around the cell once it's fully charger.  The BMS keeps track of the state of charge of every cell and controls the operation of the battery charger.

We'll I'm now going on 6 weeks behind schedule.  I'm thinking I might make a Thanksgiving completion date.

Tuesday, October 11, 2011

HVAC Detour

Beware of Simple Tasks 
The now dashless truck interior
A few weekends ago, my friend Chris was over helping with the conversion project and I said, "why don't you take out the old heater core so we can put the electric heater in."  I was thinking this would be a nice couple hour job he could work on while I worked out some wiring issues.  Well it turned out getting to the heater core required removing the entire dashboard--simple enough right?  Wrong!  Four or five hours later we finally had the dash out.  As with nearly every detour, there is a bright side to this one.  With the entire dash removed, I have easy access to all the heating ducts and was able to remove and thoroughly clean them all.  This turned out to be pretty important.  The previous owner use the truck for a landscaping & maintenance business and I've found dirt, grass clippings, and mulch debris in every crevice of the vehicle--inside and out.  I now have clean, dust-free ducts.  It's also a lot easier to clean all the crevices and niches of the dash board when it's not in the vehicle.

Electric heater core in place
The electric heater core is substantially smaller than the old liquid heater core so I had to make an adapter to get it fit into the duct properly.  This gave me a chance to learn a little sheet metal fabrication.  Fortunately I have access to a sheet metal shop and was able to use the brakes, shears, and punches to fabricate a sheet metal box to hold the electric core and fit snugly into the duct work.  It's a bonus that this whole thing fits inside a duct where it will never be seen.  It all works fine, but my first attempt at sheet metal work leaves a lot to be desire on the aesthetic side.

Old leaky master cylinder
The last little detour had to do with the breaks.  When I bought the truck there was a half-full bottle of brake fluid behind the driver's seat and the reservoir was about down to the low limit.  I soon had to add fluid to the reservoir, I figured I had some leaky cylinders at one or more wheels.  However the puddle of brake fluid under the left side of the engine compartment clearly pointed to the master cylinder.  I wasn't really looking forward to rebuilding the master cylinder and was please to find out that I could by a refurbished master cylinder at a reasonable price.  All I had to do was unbolt the older cylinder move the reservoir from the old cylinder to the new one, and bolt the new one in place.  Actually, bleeding the new master cylinder on the bench took longer than replacing it.

I've now finished most of the major mechanical stuff and am moving seriously into the electrical part of the construction.  Things have slowed down quite a bit now that summer is over.  I'm into tortoise mode-slow and steady.

Saturday, September 3, 2011

Metal Work

Cleaning up one of my
uglier welds
New Toys
One of the great things about new projects is the opportunity to acquire new tools. One of the first things I did before starting the actual project was to install an air compressor for the garage.  I got lucky here and picked up a used industrial compressor for less than $100.  The impact wrench, cutoff tool, and die grinder I got cost way more than the compressor.  In fact, the material to install the compressor (had to run a new 220v line in the garage) was more than the compressor.  So now I have air in the garage!  I also added some other tools including a 4" grinder, essential for the metal work I've been doing.  I also borrowed to important tools from friend, a MIG wire welder and a chop saw.  I would be nice to have more metal working tools, like a drill press, band saw, etc. but I don't really have the room for them in my garage.

Motor Mount
My simple motor mount
The first order of business was to create a motor mount to hold the front of the motor in place.  Initially I thought I was going to have to fabricate a rather complicated bracket that attached the new electric motor to the existing motor mounts.  However, after dropping the new motor in place, I discovered the mounts for the steering arms were in an ideal location just in front of the motor on either frame rail.  All I had to do was make plates to match the existing bolt pattern for the steering arms and then weld an angle between them and drill holes for the bolts to the motor itself.  This worked out really nicely.

Battery Boxes
Battery "box" before installation
After some considerable thought and discussions with a number of other folks who had done EV conversions, I decided I didn't really need boxes for my batteries, just racks to hold the.  The plastic shells of the batteries are really robust, and I saved weight by just using steel angles to form the frames. The image at the right shows a typical box before it was installed in the vehicle.  The bottom is 1"x1" steel angle and the top is 1/2"x1/2" angle.  Threaded rods are used to bolt the top to the bottom holding the batteries in place.  Along the sides of the box are aluminum channels (2"x1") which are connected by additional threaded rods.  These channels are used to compress the batteries.  One characteristic of the lithium batteries is they can swell when they get hot.  The swellings causes the plates inside the battery to separate and this quickly ruins the batteries.  Therefor, some way of compressing the batteries is essential.  A lot of folks use steel or aluminum plates with tie rods.  I chose the channels because they were easy to cut and the channels are stiffer than a flat plate with much less aluminum.

Bracket fabricated to attach battery
box to the truck frame
Getting the boxes mounted in the vehicle took a good deal of creativity and and a lot of work.  The basic technique was to create brackets from additional steel angle and attach the brackets to the boxes and the truck's frame.  The brackets were welded to the boxes, but I tried as much as possible to avoid welding on the frame.  Since I'm not a very good welder, I didn't want to screw up the frame with a crappy weld.  The image at the left shows the used to attach one of the boxes to the truck frame.  In this case I was able to attach the bracket to an existing set of bolt holes originally used to hold the gas tank in place.  I was often able to use existing holes as bolt locations for the brackets.  In other cases I had to drill new holes in the frame and in two cases I had to weld tabs onto the frame. Once I got the technique down, things went steadily (if a bit slowly).  The final configuration is shown below.  There are 29 batteries in the back of the truck in three separate banks of 12, 12 and 5 batteries each, plus one bank of 7 batteries up front under the hood.
Three rear battery banks

Front battery bank and motor

The next step is to design the layout of all the electrical equipment that goes under the hood.  I'll need to fabricate a box to hold the motor controller and associated gear and figure out a way to attach that under the hood.  Then will come the serious wiring work.