The home straight?

It feels like an incredible amount has happened since the last update just five days ago. I have batteries. The car is stripped again. And most of the welding and fabrication is complete.

Battery wrangles

So, I couldn’t quite let the well-priced battery pack on Facebook go. So the morning my gazumper was due to collect, I messaged the seller and offered him 50% more. He relented and after a little back and forth, we agreed (again) I would collect on Friday after putting down a deposit. After all the mucking around I wasn’t confident I would see my deposit again or the batteries. But figured it was worth a punt.

In the end the seller was a lovely guy. Just sick of being mucked around by buyers. I had an easy journey over to Bradford and back, given how bad the M62 can be. And returned with a battery pack in the boot.

The following day we craned it out of the car but didn’t get any further as we were focused on the car (below). The day after, we got to work stripping it down.

These packs are something else. Beautifully designed. Five shoe-box-sized modules are mounted in the pack along with a high voltage switch box and refridgerant cooling system. Strip the five modules out and the rest of it is incredibly light.

I got the packs out along with high voltage cables and the battery management loom. I have subsequently stripped and separated this to leave only the CANBus and power wiring for the individual modules.

This loom will plug in to a CAN transceiver and from there into a Teensy 3.2 running the SimpBMS software. Teensy is up and running and I’m just waiting on the right CAN transceiver module, which is due to arrive in a couple of days.

Battery box

Now that we have batteries we can think about how to mount them. A little shuffling around and I realised that three side by side running with the long edge parallel to the car would fit perfectly. I can stack the other two on top – leaving room for a third if I want to up the pack voltage at a later date.

The measurements for this is about 56cm by 40cm. It just so happens I have been hanging on to the frame of our old washing machine in case the steel came in useful. Its dimensions? 60cm by 43cm. Guess I’ll be using that as the basis for my battery box!

More fabrication

The other thing we did on the day the batteries were craned out of the back of the car (my wife’s: they wouldn’t fit in my Alfa GTV), was finish our game of engine bay Tetris. We worked out the location for the oil cooler and pump for the electric motor, the radiator and pump for the inverter, and the power steering pump. When I say ‘we’, what I mean is my daughter came up with good idea after good idea, proving once again that her spatial intelligence is greater than my own.

Having scribbled various instructions to ourselves in Sharpie on the existing metal, we set about removing the motor and gearbox again, along with the whole steel cage that now includes the engine mounts (I had tack welded those on at some point after the last update), as well as the mounting points for the inverter and junction box. This almost worked: it turns out the the engine mounts make the cage fractionally too wide to be lifted straight up out of the engine bay on the crane, and I didn’t notice soon enough. Therefore a few of my crappy tack welds from when the welder was misbehaving were ripped apart, leaving me a little steel jigsaw puzzle to reassemble off the car.

Starting very early this morning, I first (quietly) cleaned the engine bay down again ready for reassembly. We’ve decided not to paint it for now but instead wait until the whole car gets a respray, once it has its new body. Then as soon as it was decent to start making noise on a Bank Holiday, I started welding and grinding. I turned all the spot welds into seams at the joints and capped most of the open ends of the steel box and filled in the sections I had cut out to add captive nuts. I added (my daughter being busy today) brackets for the radiator, water pump, oil pump, oil cooler, and vacuum pump (another new arrival). I straightened up some of the brackets that had been tacked on before a bit skewed. I drilled out some of the holes for the transmission mount that were too small before (I didn’t have a decent 12mm bit). And I started making a bracket for the power steering pump (which I didn’t quite finish). Finally I gave the steel cage three coats of zinc primer and coated one side of the adaptor plate – now also a mounting point for various other brackets.

I still want to trim away some excess material from the adaptor plate as it is ridiculously heeavy. And I need to beef up the welding on the coupler, which only has a couple of tacks on it at the moment. But then with a few coats of paint, the major fabrication is done and we can start to put the engine bay back together for good (or until something goes wrong or we decide to do it all differently.

Incidentally the upgrades to my welder were a partial success. I managed some half decent welds (pictured below), which seemed to be impossible before. But some were still absolute poop (not pictured below to save my shame). I think it’s probably a combination of wrong settings and poor surface preparation now. But the welds are now strong at least, even if they aren’t always pretty.

Junction box

Perhaps the most unexpectedly time-consuming part of this whole build has been the high voltage junction box. I finally completed the mounting of all the components this week, setting the resistor down on the mounting plate with thermal compound, trimming all the mounting screws to the right length, and routing the wiring through some 3D-printed retainers. I also drilled the case and fitted the glands for the 35mm2 cables, and mounted a 16-way locking connector for all the control signals. Oh, and I also made up the cable to connect up the ISA shunt, an additional monitoring device that will give me detailed information about battery performance. Last job is to solder up the 16-way connector. Fortunately, I hadn’t yet done this when Jamie corrected my understanding of the way the inverter control board drives the contactors and relays in the junction box. Turns out I can do away with the relays I was using to switch these connections and run them straight off the board, simplifying things greatly.

And that will do for today’s update. Especially since I’ve just realised that in spite of all of the above, I have hardly taken any photos!

BMW 330e hybrid battery pack
Lid off BMW 330e hybrid batter pack
330e pack close up
330e pack junction box
One decent weld

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