SalvageS10 Build Thread

[thingstodo]

The VFD sections:

Cabinet 95
Output Section A 30
Output Section B 30
Output Section C 30
Diode Section 40
Bus Bar 20
Capacitors 50
Capacitor bus 35
Terminal block 25
Fan 10
Power Supply 10
Lugs, fuses 15
Control Board 1 15
Control Board 2 20
Control Board 3 15
Cover, keypad 5
Total 445 lbs

After removing all of the parts from the frame, I removed the frame easily - it came off as I expected it to with all of the parts bolted to it. The problem was that I was not expecting the contents to weigh 445 lbs.

While putting the parts back into the frame, for convenient storage until I can get them cleaned, the cabinet was standing on end. I went to lay it down flat, forgetting about the weight. It came down a little harder than it should have. I had decided not to trust the output transistors anyway. Dropping the cabinet on the garage floor just sealed the deal.

It was still careless and stupid.

[thingstodo]

Here are a few pictures of the VFD and cabinet before labeling and disassembly

[thingstodo]

Measure how much force (in pounds) is needed to move SalvageS10. Use the existing engine and transmission. The truck normally starts (gently) when put into gear and the engine run at idle. Reproduce this and measure the force exerted.

How to measure the force that the truck puts on the ground (and uses to move the truck forward)?

An ordinary bathroom scale should be able to measure this. A truck that is stuck in winter can be pushed out by one person. The force required to move the truck should be less than one person leaning on the truck, maybe 100 - 200 lbs.

The scale measures weight pushing down from above, perpendicular to the scale, when the scale is level. To make one scale measure the whole force, I need to stop one wheel from turning. Drill the 2 x 6 for the bolt pattern on one wheel, fit the 2 x 6 onto the studs and jam it against the ground so that it won't turn. The other wheel should exert the force for both wheels, since the force would be equally split between the two wheels if both were free to spin.

1 - jack up the truck, put it on blocks
2 - remove wheels
3 - jam the passenger's side with a 2 x 6
4 - drill out another 2 x 6 for the driver's side wheel
5 - mount the 2 x 6 horizontally
6 - mount a vertical 2x4 to the 2 x 6
7 - shim a bathroom scale to level so it reads properly
8 - zero the bathroom scale
9 - set up a video camera to show the reading on the scale
10 - start the truck and put it into gear

[thingstodo]

The sketch shows the rear hub, the horizontal 2 x 6, the vertical 2 x 4, the scale, and the video camera.

The measurement on the scale reads about 180 lbs. This is at 15 inches from the center of the wheel hub, the radius of the rear wheel. So this is the force exerted on the ground to move the truck forward at idle speed.

Press the accelerator gently, check the force on the scale

I saw the weight go momentarily up to 240 (maximum for the scale)
- then the back of the truck lifted off the ground
- then the 2 x 6 on the passenger's side broke and the passenger's side rear wheel started to accelerate

Check the available internet information. From EV Calculator with a 1994 chev s10 extended cab, an ADC FB-4001A motor, Concord 12105 batteries, a Curtis 1231C controller, 96V battery pack, 205/75r14 tires, 0 incline, 0 headwind, default rolling resistance and brake/steer resistance, the torque required to run the truck at 10 mph (the lowest calculated speed) is 41 foot-lbs at the motor. Put through a 3.43 rear end, 41 * 3.43 is 141 foot-lbs. With a 15 inch radius, that gives 141 foot-lbs * 12 inches/1 foot / 15 inches = 112 lbs of force. This is relatively close to the 180 lbs of force measured by my crudely constructed system.

The left sketch is an overhead view looking down on the rear end. The right is a side view from the driver's side of the truck

[thingstodo]

I need to find out some clearances and verify a couple of measurements. Maybe it's time to remove the back of the truck.

Remove the cargo box from the truck
remove the skid plate below the gas tank
remove the gas tank
install a target for the tachometer on the drive shaft
verify the gear ratio on the rear end. Jam the passenger side wheel. Turn the drive shaft one turn with a pipe wrench. Count the revolutions on the driver's side rear tire.

3.5 revolutions of the drive shaft to 2 turns of the rear tire. If the passenger's side tire was not jammed, each tire would have turned once. The internet lists 3.43 to 1 as a typical gear ratio for the rear end. That's likely what I have. The other option appears to be 3.73 to 1.

I tried a few different ways to jam the accelerator and measure the rpm on the drive shaft with the tach. No success.

[thingstodo]

I should be paying more attention

The input stage of the VFD is normally 6 diodes and takes the 3 phase input and generates a pretty stable DC output with a smaller AC wave 'on top' of it.

This VFD, for some reason, uses something else. There are three sets of input semiconductors, but they don't look like the output transistors. They definitely have control signals going to them.

[MPaulHolmes]

It might be 3 SCRs. I used those once to make a 3 phase rectifier.

[thingstodo]

This is one of the surplus DC/AC inverters that I have.

The idea is to use the isolated DC/DC section, where 12V is boosted to around 150 VDC, before it is converted to modified sine wave.

I got this surplus. The manufacture date is 2004, so it's not exactly leading-edge technology.

I did manage to get the screws out. The heat sink splits into an upper half and a lower half. There is a 'power board' on each half and an 'electronics' board that sits between, on a lip between the halves of the heat sink.

There are several signal cables going from the electronics board to various locations. The power to the electronics appears to be unfiltered input voltage (10 - 15 VDC) which goes through a small regulator. The electronics board has a dark flash-burn on the bottom and a couple of resistors that have corroded badly.

The majority of the control signals appear to be switching signals to 32 power transistors that switch the 12VDC through 16 step-up transformers. There is a pair of 35V capacitors and a pair of transistors for each step-up transformer. I was expecting diodes to rectify the AC pulses from the transformers, but I don't see any. There are 8 larger 200V capacitors which appear to be for the output stage, along with 4 inductors. There are a couple of smaller capacitors between the large capacitors. One of these has corroded off.

Each step-up transformer has a 40A automotive fuse. All of these appear to be fine.

I pulled all of the fuses and put regulated 12.8VDC at 0.9A max into the power feed. The power draw is about 0.3 amps.

Turn off the power and put a pair of fuses back in - far right top. Apply power - the same 0.3 amps draw. No output power. No power indication on the display. No noise.

Check a few terminals within the circuit. There does not appear to be signal switching on the electronics board. I don't expect that any of the switching transistors are stepping the 12V up to 150 VDC, or 75 VDC, or whatever the design is.

Turn off the power and put a different pair of fuses back in a different location - far left, bottom board. Apply power - same 0.3 amps draw. Check power on the electronics board. 12V in. 5V regulator is working. No signal switching. Check the intermediate outputs on the bottom power board. Nothing.

Re-assemble, put the cables back together approximately as it was when I started. This is a source of parts for further experiments. If I can figure out how the display works, that might be useful. Put the 40A fuses back in - again, convenient storage. Label as 'parts' and as 'badly corroded'

I have other units to test. I guess it's time to move on to the next one. Not a lot of useful information from this one.

[Ken Fry]

The Chevy S10 EV pickups that were made a little over a decade ago had AC motors and fairly compact controllers. Although it might not be as much fun, finding one of those would save you a lot of time. Also, because the motor was designed as a traction motor, it is relatively light. Ditto for the controller, which might have been 30 lb or so.

The EVDL Forum could offer help -- there are loads of S10s and Ford Ranger pickup conversions out there.

EVDL Archive / Forum Interface - Electric Vehicle Discussion List

[Ken Fry]

I noticed that you wanted to know the force required to mover the truck.

You can assume that the truck will weigh about 5000 lbs.

30% grade is a reasonable minimum hill climbing capability. So, you will want a tractive force of 1500 lbs. Tires for an S10 can range from 25.5 to 28 inches in diameter. We'll pick 24 for simplicity, because then the radius is one foot. That means that a little more than 1500 lb ft torque is required, (more yet for larger tire sizes). With a 3.43:1 rear end, you'd need 437 lb ft of torque at the input to the rear end.

You need to decide what sort of top speed you want, to see if the gearing for 30% grade climbing will also give you adequate top speed (based upon the motor's max rpm). If not, then you'd need more than one speed in the transmission.