During my test run up and down the road the other day, I was too nervous to observe everything accurately, so I want to renew the test drives asap after I've fixed the faults that emerged.
1. The motor fan failed to come on, and when I checked the motor temperature ten minutes after coming home, it was still over 90deg. Perhaps that had caused a power time-out I had experienced.
It was just due to a poor solder joint on the control FET.
2. The power steering pump fuse blew, so I replaced it with a 25A fuse. It blew again, so I went to 30A. This time it lasted longer until I used full lock. I'll try 40A. Since the pump wiring is all 2.5mm^2, and the full lock moments are brief, I'm not concerned that this would cause problems.
3. As described earlier, the heater control is being re-worked.
4. I had installed the coolant flow pump and reservoir early on in the build, and it was not until I had mounted the Wavesculptor that I realised that the reservoir was slightly below the level of the Wavesculptor's coolant block. I made up a revised bracket to raise the pump about 40mm to keep the coolant head above the aforementioned block.
5. The BMS master readout goes bananas when significant current is drawn by the Wavesculptor. Yes, there's interference. It disappears when the Master re-sets. This problem may be more difficult to treat, but it's one of those issues that can wait until I've had the car approved and registered.
6. Another job which has nothing to do with the drive, is that over the last year of fiddling around, I've managed to ruin the 17Ahr gel-cell auxiliary battery, probably by flattening it with interior lights from open doors and suchlike. Fortunately I bought a spare a few months ago; replacement entailed detaching the two ends of the four-cell pack in the boot.
7. I had not yet tried to control the PS pump by the car's speed. This was mainly because my old oscilloscope died a couple of months ago, and I have only just overcome my stinginess to buy a new one. I hooked up the new 'scope to the vehicle speed signal which emerges from the Instrument Cluster (X17 pin2) and goes to several modules around the vehicle: the radio, climate control, cruise control (now removed), and wiper module. For 3-series BMW owners, this is a 0.5 black/white wire. The signal is 13V or so at rest, with short negative-going pulses at speed, supposedly 13 pulses per 10km/hr, though my speedo seems to think the ratio is 1.2 not 1.3.
My initial set-up was to have three pump states: full-on; part-on and off, with two 5k 20-turn trimpots determining the transition set-points. Full-on draws about 18A at wheel centred, and part-on draws 9A. The set-points remain to be adjusted after actual driving experience. I have not yet tested this on the road.
I've been foolish: I put a Nanfeng 50A contactor from EV works in the heater control. I have one as my auxiliary contactor, but I forgot that that one never breaks under load as it operates simultaneously with three Kilovacs which split the pack. Result: my first smoke.
My other foolish omission was failing to test the shunting side of the BMS cell top boards when I checked them after they'd been soldered up. So far three have failed to shunt and have had to be replaced. But in an amazing piece of luck, they are all among the 37 boards in the boot and easily accessed.
This fault appeared when I charged the pack up to the charger's maximum voltage of 401.5V. The BMS master showed a cell sailing on past 3.6V and showed which one it was. I replaced the board and the same process was repeated with another runaway board.
