Public Charging

3 Stage Charger

Seen here is the majority of the 3 stage charger.  Each stage consists of a 100UF 370VAC Run type oil filled capacitor coupled to a common 50A bridge recitifier by a 25A solid state relay.  This makes a constant current source (though in practice it varies based on charge level), each stage contributing ~1.7A of charge current when switched on.  Charging begins with all 3 stages on, continues until 1 battery group reaches the gassing voltage (~14.1v for gels), cuts back to 2 stages until a second group reaches the threshold, then holds the final stage on until all batteries are “full”.  At this point a 1.5hr “accelerated finishing charge” is applied at 1.5amps as per the MK gel charging manual.

If this is completed without interuption then the charger shuts off and waits for a discharge cycle before starting the cycle again.

Visual Update

More progress

Some of the cables are left disconnected in these pics; these are the jumpers between groups.  These are the last to be installed, this minimizes the number of instances while working that lethal voltages are potentially present.  First jumpers are installed between every other 12v segment to create 24v groups, below the lethal voltage. These are then jumpered to create 48v packs, this is when it starts to get dangerous, and any action around the batteries is thought out carefully beyond this point as to eliminate the risk of a dropped wrench, accidental shock, or any other hazard associated with high voltages with a great deal of current potential.  All tools used around or in the engine bay are covered entirely with heavy duty heatshrink tubing. 1″ Works well for smaller wrenches. Electrical tape could also be used but I’d rather not get my tools covered in a sticky residue if possible, the heatshrink (being of the non-sealant variety) cuts off with relative ease at any time.

240zev SOLD! Pictures, progress, new specs

The configuration has changed in anticipation of a sale to a new owner in Boston.  Power is now supplied by a bank of 30 u-1 gel batteries, 33ah each.  Peak power is sacrificed for increased total capacity and better life under deep daily cycling.  They are arranged as 10 groups of 3, 6 groups (18 batteries) in the front and 4 groups (12 batteries) in the back under the floor of the hatch.  Total pack weight has decreased from 780lbs to 720lbs while total capacity increased to 12,000 watt-hours.  The use of lighter gauge steel and nylon straps to secure the batteries resulted in 40 lbs of reduction of battery hardware, plus at least 20 lbs saved by using 1awg cable instead of 4/0 awg.  Safety is being improved by moving all traction wiring outside of the cabin as well as the installation of a second contactor for full pack isolation while charging.  The 1000A controller will be turned down to ~700A to better suit the current limitation of the gels and to better suit the normal driving conditions expected.  Additional pictures will follow as the vehicle is readied for transport to its new owner.

13th Battery Frame Completed

2 8″ sections of 3/16th 2″ mild steel angle were welded to the left motor support. These are many times stronger than necessary for the task of supporting the battery and are largely intended to further brace against the torque of the motor. The entire battery support frame / motor mount was coated with 3 coats of POR-15 rust protective paint. The motor mount support tubes were capped with epoxy before being coated with por-15 to seal them from interior rust.

So now I need to fab up a hold down for the 13th battery, jumper it in and re-locate the most-positive point. I am also in the process of re-wiring everything so that it will pass inspection in a few days. New wires must be run for the blinkers, brake lights and horn.

Odyssey Discharge Characteristics

This chart demonstrates the reduction is usable energy from high amperage discharge. At the highest reported discharge current (570A) the cells deliver just 19Ah over the course of 2 minutes. I am more concerned with the 1hr and 30min specs, as these correlate with the amount of current usable for my commute with and without the ability to charge at my destination.

By plugging all the values appropriate for the 240z into this handy calculator I get a pretty good estimate for the current draw at different speeds for various incline and wind situations. It happens that the 30min draw of 96A works out to be about 70mph on flat ground, while a draw of 53A is 55mph. I also see that I can travel 30mph for 5 hours, or 90mph for just 12 minutes.

Bussman 800A Fuse

The Bussman 400A fuse just wasn’t up to the huge amp draws possible under hard acceleration so it had to be replaced. This is by far the biggest fuse I’ve ever seen.

Protective Boots

Protective boots for the battery terminals will provide protection against a catastrophic event such as a piece of metal being dropped into the battery bay. 3,500 Amps of short circuit current is not something to play with.

Lucky Number 13

A 13th battery was purchased today. This bring the voltage up to 156 volts from 144, and the total pack capacity up to 11,700 watt hours from 10,800. This is a 8.3% increase in available energy. I expect to see slightly more than an 8.3% increase in range however. This is because of something known as Peukert’s effect, which basically states that the more quickly you draw energy from an electrochemical cell the less total energy can be extracted ultimately. This holds true conversely; the more slowly you discharge your batteries the more total electricity they will provide. Say I’m traveling down the road at 50mph and consuming 100 amps at 100 motor volts.

Volts * Amps = Watts

100V * 100A = 10,000W

In this case the vehicle is consuming 10,000 Watts of energy. The batteries are not being discharged at 100A as you might expect, as the motor controller acts as a “power converter”. If we have a 144V pack voltage the amp draw from the batteries can be calculated thusly:

Motor Watts / Battery Volts = Battery Amps

10,000W / 144V = 69.4A

So 100A at 100V to the motor consumes about 69 Amps at 144V from the battery string. But now if we increase the battery voltage to 156V by adding an additional battery.

10,000W / 156V = 64.1A

The motor is drawing the same amount of power from the batteries, but because the pack voltage has increased the current required decreases.

Headlights, Etching, Cooling

I have begun work on the electrical subsystems. The 12v will be handled by a Iota 55Amp 96 – 190vdc DC/DC converter, along with a small auxiliary battery to power the initial contactor activation to switch the traction circuit on.

I’ve also begun etching the new battery rack/motor mount for coating with POR-15. I am also creating a new front wiring harness. I upgraded the original setup which routed the headlight power through the physical switch in the steering wheel, with a pair of relays switching straight to the 12v system’s battery. This should bring the voltage at the bulbs from the ~11.5 volts it was previously up to 13.6 volts from the dc/dc. I’ve heard this makes a significant difference with the dim old headlights of this 38 year old vehicle, as well as removing the biggest strain on the aging wiring. All front headlight and side marker connectors were replaced with OEM grade dual gasketed weather pak connectors.

I’m also etching the front and rear battery rack components. Also shown here is the contactor brackets made from 1/8″ steel flat stock.

I also fabricated a proper foot controlled throttle using a 25k potentiometer. This worked out so that the ~70* of mechanical throw from the original throttle setup became a steady linear range of 0 ohms through 5k ohms. A spring provides positive return and a very nice amount of pedal resistance.

I set up forced air cooling for the kostov motor. An automotive blower provides several hundred CFM of airflow through the motor. It was oriented as to swirl through the brushes before exiting the motor. Testing shows that even after several minutes of acceleration with many huge amp draws through the motor (600+ amps)the exhaust air was only warm, and the case barely warm to the touch. The blower draws approximently 10 Amps free air and 6 Amps when installed blowing through the motor.

The cooling setup is not finished. I must still create an end shroud for the motor to force more air to pass through the body of the motor.

Motor Mount Testing

Pretty cool considering I’m driving with one hand. At this point the throttle mounted to the gas pedal isn’t completed so I have a 5k pot held in my hand for control.

This car is absolutely the fastest, most fun vehicle I’ve ever driven. 1000 Amps spins the tires with ease at anything over 1/2 throttle in first, and with similar ease in second at lower speeds. I have not yet had it at higher speeds so I cannot comment on this aspect of the performance yet. 10+ Minutes of constant acceleration only managed to consume 20% of the pack’s available capacity.

Maiden Voyage

The video isn’t the greatest but it gets the point across. It moves!

Battery Clamp Adjustment

The battery clamp bars were adjusted to allow more room to access battery terminals.

Shots of the completed “engine” bay with the new clamp spacing.

Motor Mounted

The motor is mounted! And wired! The battery crossmembers have been welded to the frame in preparation for the maiden voyage. The motor controller is wired, sans 3 throttle wires.

More 4/0 gauge cables have been made for the 4 rear batteries. Due to the length of the copper lugs used the connection between the 2 middle batteries sticks out between the seats. It looks a little weird but this is preferable to modifying the placement to leave a gap, or mounting them with what would essentially be a rigid bridge between the terminals. The mechanical stress of the automotive platform could easily lead to material fatigue and ultimately battery failure should such stresses be imposed upon the terminals.

Motor Mount Mockup

I installed the motor cradle to the motor via 4 1/2″ 2″ hex bolts.

Here I am checking clearances and making sure the 27″ steel sections slated to secure the motor mount to the frame fit properly. These extend to the third battery crossmember and will be attached to all 3.

Next step is to get everything bolted together. I plan on welding all connection points but not until I am sure the driveline angle is correct, the motor is properly centered (this car has the motor offset to the passenger side), etc.

Motor Mount Construction

I picked up all the steel I need to get the car on the road.

5 Sections of .125″ wall 1.5″ square steel tube. Enough to finish the front battery hold down and mount the motor. I had them bend a 3/16″ steel plate 12″ X 24″ into a “U” with 6″ tall sides. This will cradle the motor and provide a mounting point for the 4x 0.66″ motor holes.

It was drilled to match the motor.

They Spin!

The wheel spin test is a success! The clunking heard at the beginning is because the motor is not completely secured yet, it is still suspended by the shop crane. Mainly I am listening for vibrations that would indicate the shafts are off center, of which I hear none. In 1st gear it is drawing 32amps to spin the wheels with no load, which equates to only 374 watts at 12v.

Motor Officially Connected to Wheels

For the first time the motor is officially connected to the wheels. The placement of the coupling point (driveshaft flange to differential flange) makes it exceedingly difficult to access. The mounting hardware was completely replaced with grade 8.8 hex bolts, M8 1.25 pitch.

Front Battery Rack Progress

I finished work on the front battery clamp bar. It is 2″ 3/16″ mild steel L-angle. This will spread the force of the 4 battery clamps across the 4 perpendicular battery support members. Hopefully I can get a picture that demonstrates this.

Rear Battery Rack

I went to the local steel supplier today intending to buy all the steel needed to finish the front battery rack, the rear battery rack, and the supports for the motor mount. I arrived home with 3 measly pieces, all of which had to be cut from scraps left over. They were out of steel square tube. What good is a steel supplier without steel? Though frustrating I did at least get what I needed to finish the rear battery rack. It is comprised of 2 sections of 1.5″ 1/8th wall square tube, each end with a bored 1/2″ hole. Plated 1/2″ threaded rod clamps this to the unibody with a 6″ long 1″ wide 5/16th steel plate to spread the load. Additionally there are 2 1″ 3/16th steel angle sections running the length of the pack to ensure that the batteries are level and the clamping force will be evenly distributed.

Motor Install Attempt #2

For this install attempt I removed the driveshaft from the differential and slid it into the tail shaft before lowering it into place, keeping the oil sealed in the transmission. It was then bolted into the original transmission mounts. Because the motor mount it not fabricated yet it is resting on a jack for proper placement and is still attached to the shop crane as a safety consideration (should it slip off the jack). The radiator mount was also cut to accommodate the front batteries. Next step will be to the purchase steel needed to fabricate the battery hold downs.

Motor Prep

Things didn’t go totally according to plan. I filled the transmission with a synthetic oil to replace the old gunky oil that was drained. Unfortunately this was so much less viscous that what was previously a slow dribble of oil when the transmission was tilted to remove it became a steady flow of the 1.7L freshly filled and the lowering attempt had to be aborted before it lost more than the .3L of oil I had remaining could replace.

A Picture Is Worth 1000 Words

Major Progress

Where to start…

I was able to do a test fit of the transmission to the motor. I will align these accurately, mark their positions, and drill the motor mounting holes using the wooden jig. This will give me a motor whose shaft is perfectly centered with the transmissions when both are bolted to the adapter plate.

The hub is permanently attached to the motor.

The motor controller is mounted to the firewall. The rust is because this was the previous home of the flooded lead acid battery that spewed corrosive gas for decades. It will be neutralized and painted. I had to fabricate a mounting bar for the final mounting point where there was no sheet to clamp against.

I also have begun brainstorming about ways to mount the support electronics to some sort of plate. Mounting them to an aluminum plate and then mounting the plate as a unit will be much easier than trying to drill and mount each component to the firewall (which means working under the dash on the reverse side) seperately. It should also make it much easier to make modifications later. Shown here are 2 SW200 contactors, 2 1000A shunts, and a bussman 400A 170vdc semiconductor fuse.

Motor Adapter Progress

Finished…

Now I need to transfer this pattern of holes over to the aluminum plate, making sure that down for the motor’s mounting feet is correctly oriented to the transmission’s mount.

Motor Adapter Plate Pattern

The mounting holes for the motor must be perfect. In order to facilitate this I am going to first create a pattern out of plywood. This will allow me to do two things. First, to verify that the spacing is correct by mounting this piece to the motor itself. Secondly, this pattern can be used as a jig while drilling the mounting holes in the 1/2″ aluminum plate. Here the pattern is in its beginning stages.

Connectors

The Anderson SB350 4/0 gauge disconnects arrived. The pair of these will be used as an emergency disconnect in the event that the main contactors weld (considering the Odyssey batteries short circuit rating of 3500 Amps I’m a little worried about this possibility). There will be a fuse in the traction loop as well, but considering I’m going to be strapped into this device I’m all about multiple redundant safety disconnects.

I also received a package of weather-pack connectors for accessory wiring. The wiring on this vehicle is going on 39 years old, so critical systems like headlights and brakelights will be completely re-wired. Seeing as they wil be exposed to some very harsh conditions (daily freeze/thaw, corrosive salt spray, etc) the connectors are fully gasketed. This is a must for any automotive wiring.

Motor-Transmission Adapter

The motor to transmission adapter hub finally arrived. The lack of this part has been impeding my progress for weeks; due to uncertainties about the exact spacing of the motor/transmission I have been unable to weld the battery trays in place, and therefore also unable to run any wiring.

First thing after opening the box I took a sawzall to it. I’m not using a motor spacer so the additional length was unnecessary.

This makes it possible to finish machining the motor-transmission adapter plate. The hub makes it possible to perfectly align the shafts so that the motor mounting holes can be drilled precisely.

New Battery Mounting Ideas

I’ve been experimenting with new battery placement ideas.

This gets the batteries further away from the engine in the back, which could cause issues due to heat. A battery is basically just an ongoing chemical reaction, and the speed of this reaction is proportional to the temperature. Batteries can produce more current when warm, which is normally a good thing (this little fact is exploited by EV dragsters), but if 1/2 of the pack is at 100*, and the rest of the pack is at 50*, it could lead to serious battery equalization issues. This arrangement avoids this issue by placing them in the main compartment, but also puts their center of mass up higher than is ideal. This could lead to excessive body roll in corners. It does also place them much closer to the center point of the vehicle, directly between the wheels, which would lead to faster steering response. I guess its all about trade-offs.

This arrangement allows for 5 instead of the previous 4 in the passenger compartment. This means I can upgrade from 144v (12) to 156v (13), which should increase range and acceleration about 8%, at the expense of 60lbs.

Same thing, except the batteries are slightly closer together, but the terminals are more exposed. This should make mounting easier, but I will need a lexan cover to keep hands away from the lethal voltages present.

1000Amp Motor Controller

Here it is, the 1000A monster:

I’m worried about melting my motor with this beast. Or grenading the transmission. 1000Amps is alot of juice.
156volts x 1000amp = 156000watts

156000watts / 750 watts/hp *.80 efficiency factor 166hp peak

I will be running it at 144v at first, so it will be 144,000 watts, or 157hp.

Battery Balancer Components

I received all the components for the battery balancing system today.  This setup is necessary to ensure that each battery is well cared for. It will intergrate with the charging microprocessor to halt phase 1 of charging (bulk stage) as soon as a preset voltage level is exceeded. This indicates that at least one cell is beginning to reach its maximum capacity. It will also monitor the pack temperature and abort charging if anything fluctuates out of a safe range. At this point the charger’s computer will signal to the balancing system that equilization may commence. The balancer will then systematically bring each individual cell up to a full charge, as well as taking care of phase 2 (absorption) charging and phase 3 (float) should it be necessary.

The relay boards will allow the balancer to select, charge, and monitor each battery individually. I have 16 outputs available, 12 of which will be used for the traction pack (possibly 13 in the future should I upgrade to 156volts), 1 for the 12v accessory battery, and 1 for the control of the balancer charger. This leaves 1 output for future implementation.

The Odyssey Ultimizer is specifically designed for the unique Hawker AGM chemistry. I chose the 12amp version so I do not melt my balancer relays (rated for 15a max).

This microprocessor will be the heart of the system. I plan on interfacing it to the charger’s status LEDs via optical photoresistors. It has 16 digital I/O and 6 analog inputs, perfect for this application.

Generator Aquired

A generator has been acquired. It is capable of 10,000 watts at either 120 or 240volts. It is belt driven which should give me much more flexibility in mounting options. Is also fits well with the modular theme; it could be removed and replaced easily with a different unit as long as the pulley is compatible.

Plugging some quick numbers into the incredibly handy EV Calculator I see that the a 10kw output should be capable of sustaining a cruising speed of 65mph on perfectly level ground. In this scenario the batteries will be used only for additional load (incline, headwind, increased speed), and they will receive the surplus output when load decreases (downhill slopes, tailwind, decreased speed).

If I then extrapolate this with data available on diesel generator fuel consumption, which appears to be 210-240 grams fuel per kWh. Therefore 1 hour at 10kw will consume 2400 grams = 5.3lbs of diesel fuel. Diesel weighs about 7.2lbs per gallon, so this equates to .75 gallons of fuel to achieve 65 miles.

Battery Layout

Because the diesel generator will be occupying all of the available space in the rear hatch, all 12 batteries must now fit under the hood. This took alot of wiggling and measuring, but I think I came up with a layout that will work well. This has the added bonus of using as little of my precious (and heavy…) 4/0 cable as possible.

I also completed the removal of the rear hatch sheet metal. Most of this space was previously for the fuel tank and the spare tire well. The diesel should fit here very nicely.

Motor to Transmission Adapter Plate

In order to mount the electric motor to the existing transmission a plate needed to be fabricated.

To make the center hole, which will allow me to mount the plate to the transmission in order to get an exact center for the motor mounting holes.

The 2″ hole was simply drilled in with a hole saw in a hand drill. Lots of lubricant (WD-40) was used, as well as a slower speed and lots of breaks. Aluminum is very easy to work with compared to steel. The plate is .500″ thick 6061. A 12″x13″ piece cut and shipped cost $80.

Close enough…

I have ordered a part made which will connect the shaft from the electric motor to the splined shaft on the transmission. It will be fabricated in part using the old clutch. Any further progress mounting the motor must wait for this.

Engine Tear Down

In order to fund the conversion, as well as a learning experience, I tore down the original engine piece by piece.

The components were sold.

Finally, we are left with a bare engine block.

All in all I made enough to pay for the purchase of the electric motor. Seems like a fair trade to me…..

Cable Making

Many hours were spent making battery cables. One must ensure that the cable is completely inserted into the copper lug before it is crimped. A good connection is essential, as any chain is only as good as its weakest link, a chain of 12 batteries has about 48 critical points ((battery terminal to copper lug, battery lug to cable) x 2 per battery)

Each wire needed to be as short as possible, but the lugs were too long to go straight between terminals. This arrangement requires very little cable, and therefore the smallest amount of electrical resistance possible, to connect the batteries.

The batteries sit on 3/16″ mild steel 2″ angle. This will be welded to the frame as soon as the motor is in place comfortably.

Electric Vehicle Drivetrain

My powerplant:

A kostov 9″ series wound 144v electric motor. Rated for 107A continous. It weighs approx. 100 lbs yet can produce several hundred ft. lbs. of torque.

These 73ah AGMs are rated to produce 1750 amps for 5 seconds, or around 70 amps continuously for one hour. They weigh 60 lbs each, with a combined pack weight of 720lbs. The total pack capacity is 10.5kwh. Their peukert’s factor is extremely low, so they deliver their full capacity to the motor very effeciently. They are also capable of being charged to 90% capacity in just half an hour, or less, if you could provide enough current. A typical 110v 15a plug will take more like 5 or 6 hours. They are rebadged by sears and sold under the “DieHard” brand as “Platinum”.

The roll of 4/0 gauge cable arrived. This stuff is heavy! I had it printed with “DANGER – High Voltage”. I also received orders of 4/0 gauge copper battery terminal lugs, and 1.1″ diameter heat shrink lined with a corrosion preventing sealant.

400 Amps continuously….no problem.

Electric Vehicles Just Make Sense

90% of my driving is the same route, every day. I commute to school each day, 24 miles each way. The drive takes me about 25 minutes and costs me about $6 a day in fuel at todays gas prices. This is with and “fuel effecient sedan” EPA rated 32mpg highway. If you factor in oil, tires, maintenence, and the depreciation over time of the vehicle each mile may cost considerably more than this.

If I can achive this commute each day using readily available (cheap!) electrons, I stand to save a considerable amount on fuel. I spent $2300 on a pack of 12 PC1750 Hawker Odyssey sealed AGM batteries that are warrantied for 4 years free replacement. Assuming the pack lasts only those 4 years, my battery costs are $575 a year. When you add electricity to this ((5 recharges/week X 52wks) X 10kwh/charge X $0.10/kwh) = $252 in electricity “fuel” costs. This makes driving electric around half as costly as driving an ICE vehicle).

Oh, and its clean, fast, quiet and fun.

Out comes the engine…..

Project AmpEater, the electric 240z

Day 0 – The stock vehicle. It isn’t going to stay that way for long….