Where does the time go in an EV conversion? Often times, in places and in quantities that you would not believe when starting off.
We've had all the battery boxes finished for months now, and we've had most of the "A" half-pack installed for months, and the car has been drivable like that. Most of the fiddly little things, with the exception of the heater and chargers, are actually done.
Lucifer must have noticed this, and decided to send down some lightning bolts to throw us off target. We had an "incident" with a routine software download, which has been working for years, and which we've even been patting ourselves on the back about how good it's been. (Maybe that was our mistake
). The nature of this incident is such that we had to take the battery boxes out, remove the lids, and individually JTAG program each microprocessor. As luck would have it(or poor design, but bad luck sounds better), the JTAG connections are at the end of the BMU boards, so one end of each string of cells (one battery box has 3 strings for just 15 cells) is under a strip of runner that is siliconed in place, so that had to be laboriously removed and replaced. Some of the battery boxes take about an hour to remove and replace. The whole idea is that this should never happen, so when it did, we had to figure out why it happened, and how to really prevent it from happening again.
That's taken about 3 weeks to write, test, and implement. The solution, which we may talk about in more detail in another post, involves two separate bootstrap loaders. That's for now; one of those should really go away, but it's simpler and maaaybe more robust to leave it that way for now. But at least, we told ourselves, it could have been worse: we could have had to take out the two worst battery boxes (for removing and re-installing); these are in the fuel tank space right in the middle of the car. By some miracle, these weren't involved in the original incident, and their LEDs were still flashing away happily.
We developed a technique for doing the repair and upgrade, and were quite confident that when we came to upgrade the software in the fuel tank battery boxes (not because they had seized like the others, but because they needed to use the new software scheme) that there would be no problems.
Indeed, the front box (which isn't too hard to get at, if as now the rollbar battery box is removed), upgraded without a hitch. But old Lucifer had one last lightning bolt for us. When we went to upgrade the rearmost battery box, the hardest one to get to, there was no echo from the front of the string of BMUs to the end. There was status information being transmitted ~ 15 times per second, but characters typed at the first BMU didn't make it to the last one. At first, we hoped that it was just that we were using the wrong pair of optic fibres, but no. When we sent a command that should turn on all the blue lights, we could tell with a mirror and looking at the right angle from inside the boot that the lights came on up to a certain point, then stopped. Shining a torch in there and manipulating the mirror, we could see that there was a break between squiggle-joined strings of cells; these are bridged with three wires that are soldered (formerly we used connectors, but these proved unreliable), and of course the wires were siliconed to strain relieve them. So you'd expect that once connection was made (these BMUs have been working for weeks at least), that they'd never come apart.
Since taking that battery box out is such a lot of work, we tried taking off the lid in-situ, and using the ~ 10 mm of clearance above the battery box to try to do something with the wires. It was a desperate move, and of course it failed. There was no hope of re-soldering the wires in-situ, and besides Weber could not believe that it could possibly be the wires that was at fault.
So even these last two battery boxes had to come out!
Things are a bit cluttered in that photo, so I'll take a moment to point out a few things. This is the back of the car; at the bottom right you can see the boot lid raised. That's Weber's hand in the top left, resting on the top of the passenger's seat, inclined forward. The white sheet is protecting the convertible roof, in retracted position. Weber assures me that as horrible as it is to remove these two battery boxes, removing the soft top roof is infinitely worse. So it stayed in place and we worked around it carefully. The two battery boxes are stacked on top of each other, resting on some planks of wood, resting on the centre console area that covers the gearbox. I don't know whether it had ever had to hold up that much weight, and I'm pretty sure it was never designed to do that. But it held for us. The infamous "16 mm" spanner can be seen in the middle at the right end of the photo. The various bits of wood are all part of the voodoo that we need to get the battery boxes out and back in again, with the soft top, two contactor boxes, and a variety of electrical wires and optic fibres in the way. The netbook computer is the one we use for communicating with the BMUs; in the top left of the screen is the Windows application for sending the binary images with the password characters at the start and the checksum at the end, and appropriate timing of the bytes in between. Not visible in this shot is the engine lifter that we use to lift the heavy battery boxes (just under 50 kg each, those two).
You can see that we have the lid off the top box. It was immediately obvious that one of the wires was indeed not connecting properly, and somehow must only have been connecting via a strand of copper. (My personal theory is that Lucifer got his finder under there, but I suppose that's just blaming the unseen for our sloppy workmanship.) It was a two minute job to repair the wire, test, and re-silicone the wires.
We must have been doing this way too many times, because it seems like we spent "only" about an hour pulling those boxes out and putting them back in. Elapsed time was much greater, because we were distracted by something else, which will no doubt be the subject of another post in a week or so.
[ Edit: added "the hand of Weber" ]