Update #17 - Paint removal #

2021-01-20

I’ve been busy with work for the past couple of months so progress has been a little slow. Mostly, with what little time I’ve had, I’ve been stripping paint and uncovering rust and dents.

This evening, I tried to figure out where I might put some of the components. In particular, the batteries. The current plan, is to use a ~10kwh pack recycled from a BMW 5 series PHEV. The pack is made of 6 modules each weighing 12.5kg and measuring approx 380x130x180mm. This pack could give me as much as 50km of range.

First I wanted to see if I could re-use the fuel tank to store all of the batteries. The opening in the car that the fuel tank sits into is big enough for all six batteries to fit. So, I took out my grinder and cut the top off the fuel tank.

As you can see, it was full of this awful rusty sludge. After grinding off the extra metal left over from my initial rough cut and cleaning out the bottom a bit, I have a tub I can put things in. Even if it still is a bit banged up - I can fix that later. This exercise is just to see what’s going to fit where.

The first (overly optimistic) attempt is to try and fit all six modules in the fuel tank tub that I’ve created. No luck. While the space that the fuel tank sits in has enough space for all six modules, the curves of the fuel tank reduce the usable space. It’s about 20mm too narrow width-wise.

One option though would be to make a battery box that sits down into this space like the fuel tank does. It could be more square-shaped than the fuel tank so fit all six modules. Depending on the clearance, I might even be able to have the bottom of the battery box sit a little lower and fit 12 modules in this space. I’m putting that option to the side for now though as I want to preserve the look of the car externally as much as possible.

One to the second plan. Can I put all six modules over the rear axle - three on top of three? Well, no. The modules are too long to fit this way - even with the BMS sitting on the top rather than on the end.

OK, plan three : put all six modules over the rear axle, but longways. And, it turns out that they will just about fit like this. But it gets me thinking. I’d like to add more capacity later. Say I want to fix another one of these packs in the boot. Can I fit them in a six over six configuration? Well, not quite, the arms for the boot lid need clearance. The top batteries would be in the way. But, I could put five-over-five over the axle, and then out the remaining two in the fuel tank. The battery box would even overhang the fuel tank, so I could route cables down through the floor of the battery box and into the fuel tank. This could help conceal the cables. Plus, I’d have room left over in the fuel tank for a rear high voltage junction box. I like this plan the most so far.

I’ve got myself a Tesla Gen 2 charger from a model S. These things can do 10kw AC charging. This will be more than enough for me to charge at home. This is around the limit of what my domestic supply will be able to do anyway. So where will I put the Tesla charger?

It fits so neatly in the rear quarter there. I think, if I go with this, I would mount it with the other side (the ‘bottom’) facing out. The mounting holes are on that side and getting it in and out would be much easier that way. I would just need to weld in a few right angle brackets in the right places. The whole thing could be covered with a timer+cloth board.

The charger could also fit in the fuel tank. But then I’d lost out on space for one battery module.

Next I considered how I might fit batteries in the front if I wanted to go that way. Really, the only good place to put them would be right up the very front of the engine bay. At most I’d say I could fit three layers of four here. That’s 150kg of batteries right in the nose of the car. I’m not sure I like that idea. Granted, these cars usually have a lot of weight in the engine bay.

Next scouting exercise is the charge port. It would be cool to have the charge port in the original fuel filler location. I’ve ordered a Type 2 CCS port - one with DC pins. I have the Tesla charge for AC charging, like I say, and, later on, I would like to implement some form of DC fast charging, if possible. The minimum space needed for the opening for the charge port is 105mm tall and 70mm wide. The height of the area where the filler hole is is 140mm - which is very tight. One possibility might be to turn the charge port horizontally rather than vertically. I’ll also need to watch the clearance behind. The receiving part for the boot latch is here.