So with the wheels turning it’s now time to see how she drives right? Er Yeah, Nah, Kinda!
Not Just an EV Conversion
This blog makes it sound like everything occurs quickly and smoothly. The reality is that there have been lots of twists and turns over the last 2-3 months with this project, details of which probably aren’t blog worthy. For example, during the engine removal process we took the opportunity to replace all of the following:
Brake pads and discs
Tie rod ends
Bottom ball joints
This was done to freshen up the front end while we had easy access. We also need to remember that the entire front subframe and steering rack has been out and the brake vacuum pump has never been tested. Then the car has obviously had a new clutch plate and the motor adaptor which should work, but has never been used on this model of car. Lots to go wrong then on a 400m test drive!
The custom loom and integration, while been unit tested, hasn't been tested with the rest of the car while it's in motion so we're expecting errors once the Audi's (unfeasibly smart) ECUs detect it's on the move.
The point is, much has happened to this little car and it hasn’t turned a wheel since, so the focus is on safety before we hit the road. We make sure every nut and bolt is nipped/torqued up and that every bit of the loom, including those bits that haven't yet been terminated, are tidied away so not to short on anything and not to wrap around anything rotational. We also make sure no tools are hiding in the nooks and crannies of the car. The final step is to connect up and thoroughly test the emergency disconnect and with that we're ready to drop the wheels on the ground.
It's all very unceremonious, nothing left to do except jump in and turn the key. Brendan just happens to be there to film, otherwise no one would be there to record it.
In this the first clip, no creep mode is enabled so when the key is turned there's no movement at all. And when you give the accelerator a squeeze there's no rotational sensation either. It's also really hard to feel the clutch biting point so our new clutch takes a beating from the get go!
We can't give it the beans because at this stage only a third of the battery pack is installed so we need to be kind to them. With that in mind, first impressions of it are thus:- It's smooth, impossibly quiet and because of the weight loss seemingly effortless to move off.
This can be seen in the second clip when John is seen driving it back. He's taking it easy on purpose but even so the drive is effortless and even though the power has been deliberately dialled down.
Also the car is now cool, it just is. Electric drive does that by default.
So what's the outcome of the test drive? It's clearly not finished but it's already awesome and there were 'No Faults Found' ;-)
In terms of charge connectors, we've decided to go for the industry standard J1772 charge port mounted in the existing petrol filler spot. We want to charge just like any other mass manufactured EV and to take advantage of public charging networks such as ChargePoint. The fabrication for this seemingly simple device was far from straight forward. Once the fuel filler pipe was removed we had nothing to mount to as the filler mounted directly off the fuel tank. So using the "can't beat them join them" philosophy, we used the same pickup points and created a filler neck of our own, only ours is designed to receive electrons rather than hydrocarbons. The way a J1772 charge port opens tickles me every time. Every J1772 port from every manufacturer opens in the same fast then slow damped manner. Cool as!
The Charger Choice
Incredibly most EV chargers can only be "factory configured" so if your battery arrangement is, say 96 volts, then later on you decide to add a few more cells (which is common on custom EV builds), then the unit will need to be sent back to the manufacturer to be reconfigured. We didn’t want that so we plumped for a custom solution. The down side of which is that we needed to code the charge controller ourselves - see the vid below for an explanation. Long story short, the cost of flexibility is risk of killing the charger or our cells. Fortunately our background in Computer Engineering/ Electronic Engineering helped us understand the logic of setup and helped prevent the needless murder of any innocent Lithium Iron Cells. The coding on the charger is far from perfect and definitely isn't fool proof so really not for the faint hearted.
Once setup on the bench, the mass of wires is migrated to the car where we hit our first placement hitch. The charger is simply too big to hide anywhere where there's ventilation so we end up mounting on the LHS of the cargo area. Not perfect and none of us are happy with the location but there doesn't seem to be any other option. We resign ourselves that perhaps once everything else is fitted we'll be able to relocate the charger elsewhere.
Rear Battery Pack - the most challenging job so far!
This represented the biggest challenge of the build thus far. My top tip for any build, start with the battery boxes! We wanted to mount our rear battery box in front of the rear axle and as low as possible and to follow the profile of the floor plan. Easier said than done! The profile of the floor plan is uneven in all directions so this took too much time to measure and mock up. We eventually resort to Cardboard Aided Design or CAD to help us understand the best shape and size for the battery box. The final design is eventually made out of galvanised steel with cross braces to enable the batteries to site firmly and securely within, but it takes 3 full days to complete by the time we've sourced the correct materials, bolted it all together, installed the batteries and connected them up to the rest of the car.
So that's the two out of three battery packs and the charging circuit installed. The car can go, stop and re-charge, what's next? Well we're now into a rolling build situation.
The build is far from finished but we won't know what faults or teething issues we have (with the completed activities) until we start driving it. So that's what we'll do. Drive and tweak while we continue the build.
So what's left? Well we still have no power steering and there's still no method to charge the 12v battery so let's tackle that next time!