1994 US Electricar Repair Blog by Mike

Fritz says the twitching on the cap voltage is due to the very low resistance I now have on the discharge load. Even though his manual says to lower it for faster discharge, he made it sound like I screwed up by trying it. Here is the url for Fritz’s homemade Dual Pulse 600Ws spot welder blog. http://frikkieg.blogspot.com/ He’s been a bit impatient, rude, and over worked lately. I think it’s time to start a forum so owners and builders can chat and exchange ideas without Fritz over reacting.

The huge 4 farad cap now has it’s delrin mounts machined and installed on the base plate. It will be held in place with tie wraps that pass through the delrin mounts. Next it will be time to cut and bend copper bar to attach the welding probes to the system. Also I have to turn the probes on the lathe. Everything is a tight fit but it’s going to work. I wanted a chassis that could fit on on of my benches. I have some great ideas how to clean up the appearance of the front panel.

You might be able to see the extra heatsinks I added to the components on each side of the cap centered in this pic. This is for days when the spot welder is being used in warm environments. I’m using fans that draw 350ma so the 24v reg will get warmer. I may connect the fans to the 36v supply using a dropping resistor so the 24v supply won’t have any extra load.

Fritz had me remove the 22v zener in the over voltage protection circuit. The cap was then able to charge to 20 volts. It did work very hard from 18 to 20v however. Q4 that drives the charging, was working far harder than usual. So I put the 22v zener back on the board. It seems that the zener limited the cap’s voltage to a perfect level. The zener has a suffix on the part number that shows it’s actually a 20.5v zener. Each voltage has 4 different levels. Mine was the lowest end of the 22v range. Fritz said I needed a full 3 farad cap in order to get to 20v. Mine only tested to 1.6 farad. It’s an audio cap rated at 4.0 farad. Why is it that audio stuff is always playing a numbers game with their ratings?

So now I have some new lower value resistors that I’ve tested on the discharge side of the spot welder. I really like the responsiveness of these resistors. But the voltage regulation has become twitchy. A bunch of mounting and fabrication of parts is all that hold back getting this spot welder finished.

Also ordered a foot switch recommended by Fritz.

Just did a light test on the fet board. First I powered it up. Then attached an ohm meter across the fets. When activated, the meter read close to zero. Good sign. Next I went and added a power supply at 12 volts, but current limited to 3 amps. Went fine. With light duty testing it seems to work. Looks like the next step is to connect it to the output of the control board and somehow simulate the load of a weld being made. The large 4 farad cap is just connected with jumpers. Nothing that can move much current. So we’ll see how that works for testing.

Still lots of machining to do. Still need to get the front panel layout designed and then machined. I still don’t have a clue how to mount it yet. The bar and round stock of copper arrived. So the welding probes need to be machined as well.

Last night until late and all day today I worked on the spot welder. Last night the ac wiring was routed and installed. Today was debug day. I found some issues that needed some help from Fritz. We exchanged a lot of emails. I suggested we open a Yahoo group to better support his efforts. Right now the welder won’t charge the main cap past 17-18v. It should hit 20v. Fritz suggested that D4 was bad. I replaced it to no avail. He suggested I check for solder issues. I re-soldered the whole board to no avail. That’s where the welder sits.

I made a list of other things that need to get done so the project doesn’t stall.

Here is some detail on the lcd that has to be done to make it work.

Here is the spot welder control board and lcd being brought up for the first time. Very satisfying. Next the fet board has to be tested as there are reports of new fets being bad. My first suspicion was that the builder’s were not ESD savvy and popped them with some static electricity.

The Spot welder hardware being mounted to it’s platform that will slide into it’s chassis when done. Aluminum box tubing was used to heatsink the bridge rectifier and the discharge resistors. The fans will hit them with good velocity to keep them cool, but yet not impede the airflow too much to the rest of the system.

Rear panel was milled on my CNC for the fans, fuse holder, and power cord that were used in the original Tektronix chassis, but relocated.

11jan2011 22648 miles, recharged pack, +4.98kwh, 11.88kwh total, no o/c time. Refilled bearing reservoir with Mobile1.
10jan2011 Flattened entire pack. Jumpered redtop cells.
10jan2011 drove deep discharge, -6.90kwh.

Watered entire pack, 22627 miles, many cells very low. 3.7 gallons H20.

Set charger to 2 minutes of constant voltage time.

10jan2011 22627 miles, watered entire pack. Many cells very low. 3.7 gallons H20.

09jan2011 Drove, deep discharge, -6.93kwh, recharged 2.77kwh, 9.70kwh total. Pack was very stiff during charging and driving.
09jan2011 Recharged flattened pack, +5.88kwh, 11.18kwh total. 20 cells appeared shorted. After 30 minutes of charging they all appeared normal. Cells are marked with a red circle on their cap.
08jan2011 Flattened entire pack, -5.30kwh, 18.9ah, 19.1miles, 11:35pm.

07jan2011 Recharge.+2.94kwh, 8.73kwh total.
06jan2011 Drove deep discharge,-5.79kwh

06jan2011 Recharge, +2.18kwh, 6.53kwh total.
05jan2011 Drove deep discharge, -4.35kwh

27dec2010 Added 10 used and tested nicad cells to pack. 251 total. Set charge voltage to 400vdc.

16dec2010 +3.86kwh (8.3ah) on recharge. 11.19kwh (35.7ah) total recharge.

15dec2010 +4.55kwh on recharge. 11.59kwh total recharge.

15dec2010 -7.33kwh (27.4ah) @ 30.1 miles, 244.3wh/mi, dry, sunny, warm. Errands, highway and city driving. Heater. SJ loop.

14dec2010 -7.04kwh @ 27.7 miles, 254wh/mi, raining, cold, dark, no no heater. SJ loop.

241 cells installed. 2 shorted green top cells removed. 24 Redtops watered. 3 clear tops watered.

27nov2010 -4.55kwh, 20.3 miles, 243wh/mi

26nov2010 -4.13kwh, 15.55 miles, 265wh/mi

This week getting more done on the spot welder has been my goal. There is a lot of details. I got more parts from Halted. The fet board in now tested and fully modified and assembled. I’ve gutted the chassis that the spot welder will be mounted into. It’s going to be a very tight fit. I’ve cut a base plate to mount the electronics onto.

Here is the modification that Fritz has everyone do to their boards. We are suppose to just use a piece of solid wire down each open path. I used copper plate to make it even more robust.

To help keep warmer parts cooler, they get mounted up off of the pcb.

With my experience with motor controllers, it seemed prudent to add a schottky diode and 10 ohm resistor to each fet’s gate pin. There is an issue with ringing on the fets. We are suppose to add a board full of schottky diodes to lower the ringing’s peak value to less than the voltage rating of the fet’s diodes. I used a pointed spiral bit for cut across each gate’s trace. The gap is just wide enough so that an 0805 sized resistor can fit across it. I used a 1/8″ endmill to remove the green solder mask to make solder pads for the new components. A very light touch was required to remove the solder mask without removing any copper. I used my Bridgeport mill for this mod.

Here the parts are mounted next onto the gate’s trace. A perfect fit on the width of the trace.

Here is 1 of 3 heatsinks with fets mounted, ready for pcb installation.

Here they are with the heatsinks mounted. The one row of parts on the right, just clears the heatsink due to the double sided foam tape thickness. I still had to space the heatsink up off of the pcb a little more so that it did not contact the delicate glass diodes. The other two rows of parts were totally clear of the heatsinks.

I found on the Endless Sphere forum a BMS that matches my needs and philosophy of being simple, but with a processor. Here is the link. He talks about his design as he builds it in other threads. I just don’t see anything since late 2009 on the progress of the design. I’ve emailed him. We’ll see.

Here you can see his prototype layed out. It communicates using infrared leds. That helps get around the EMI issue.

Tonight I finally got this system debugged. Turns out it had a bad transformer on phase A. Runs smooth as glass now. I left it outside since it’s so cold here now. This will cold soak the Dolphin and help to test if it’s prone to classic dropouts or not. Cold and humid weather pushes any marginal board right into classic dropout mode. Clunk clunk!

Got another customers board today from Hawaii. It needs the dropout mod and also I’ve been requested to add the 70kw upgrade. Busy weekend.

I have have gathered up all of my individual schematics of the Dolphin system and am drawing them up to make a master schematic.

Since I’ve been hammering away at debugging this east coast system, I built up another system to help me. So now I have another completely assembled system that runs.