Well, bit off the radar with this one!
In reality, I was balls out building the Audi, all the time in the world from May to September '20 when I finally ran out of money but managed to get a job but finished (almost) the build. Still no excuse for not updating here so here's a round-up of what I have done since the end of last year when I decided to partially strip the car apart with the aim of getting a working BMS. Firstly, I had to see how it handled the snow over the winter...
FIrst up, as promised too many times, I got stuck into the new brake servo. Remove the old hydraulic system and slide in a tried and tested vac system with a servo from an 80 Cabrio, a UP28 Hella pump from a Jag, vac sensor from a Mk4 Golf, a vac reservoir from an A8 and finally a mosfet switch to do all the switching on and off, courtesy of Johu. All bench tested and then finally installed, it works a treat.
After that, I went and tackled the job I had been putting off for ages and dropped the rear pack. Not too bad in the end and came out pretty handy. With that however came out the charger, rear HVJB and all the fittings. I have already committed to building a proper sealed battery box though in CAD and getting it made up with proper HV connectors and the like. Next was to retrieve the BMS and open it up... which was ugly. I must say, the box did a great job of keeping the magic smoke in though
The plan, aside from swap the BMS for one less charred, find out what the hell happened and replace. I went back to where I had had multiple changes of heart when wiring up the voltage taps on the separate 4 module pack in the front and with a heavy amount of documentation found that yep... I had friggin mixed up 6 taps. Bugger me. While I was at it, I re-checked every tap in the rest of the pack so I was 100% before bottoming it all up again. As you can see in the pic above, I extended the rear pack wiring out after a couple of nights making up 2 x bms jumper looms so I could have the BMS in the boot.
I could have simply done a solder joint extension but had a few molex connectors and crimps so, went that direction. If anything, honed my crimping skills. As I was on a roll, I decided to tidy up some LV things up front that I had let go, like putting in some 80A fuses for the PS pump and between DCDC and 12v battery. I also put in a 12v isolator switch (see it in the bottom pic on the RHS) and a new safety inertia switch fitted to the bulk head to knock out the 12v power to inverter and VCU in the event of a shunt.
A few other things I decided to do also were to upgrade the messy DIY shielded HV up from for proper 50sq shielded cable from HVJB to front pack and from front pack to 4 pack. Really tidies the bay up and just gives me a another piece os mind I have brought the standard up a touch.
All this had me on a roll and was well chuffed after months of not doing anything due to work and family commitments. The day came to put it all back in. It looks brilliant! Re wired the BMS connectors, following all detail directions, to work with the later Leaf unit and plugged them all on, one... by one... 1, 2, 3, 4,, 5... FIZZ POP!!! Two or three little sparks rose from the board.... BOLL@CKS!
Long story short... I left it for 3 weeks. Just glanced at it when I passed by the car in the garage and then took the board to the bench. What the hell... when I tracked the damaged diodes back to the connector... it led me to cells (in around 73 to 80 in the front pack. What the hell?? Popped the lid. Continuity checked... everything... top to bottom. Perfect. CHin scratch. I then removed all the bus bars.
All the way along from Cell 96 back 3.98v, 3.97v, 3.98v, 3.99v......0v... 0v... 3.52v... Oooooh kayyyy. In a nutshell, for whatever reason, in the process of only 3 charge and discharges, with no BMS, three modules have shat themselves. Anyway.,... thanks to the OI and Course past pupils in the community, within the space of a day I had sourced 4 (yes 4... in case) new modules AND a replacement BMS... I'll use the one I popped for spares. So, it'll be front pack out, see what the hell happened. More than likely they suffered from voltage drop rather than an over charge. Interested to see if there was any swelling...
On that bombshell, I hope to get the car moving again very soon as It's well overdue a spin.... Always carry protection kids. Always use a BMS