Very, very tidy job there. Many of the EV's you see on the net look like they were just a spare washing machine motor (even though they very, very rarely are) thrown into a rustbucket the owner also had lying around (or bought for $50) - yours looks very professional.
I've been doing a bit of reading about this myself lately, although I can't claim any of the practical experience you have Phill! So correct me if I'm wrong here...
Regenerative Braking is generally not done on DC EV's. Generally, Regenerative Braking is something that is done using the vehicle's main motor to recharge the batteries (rather than secondary alternators, etc) with an AC motor setup. Everything I've read indicates it's significantly harder to organize regenerative power on a DC setup.
The info's probably out there somewhere, I just didn't look hard enough to find it.
I'd guess it would probably be achievable to rig up separate charging alternators that were somehow rigged to the controller so that they were only active (i.e. charging, draining kinetic energy) off throttle, but that's extra expense, extra weight, more things to go wrong... There's also the question as to how much you would actually gain. The best alternators they're putting in cars nowadays are what, 110A @ 12V (nominal), maybe a bit more? Convert it to 156V, you're only charging at about 9Amps (before losses), and only in short bursts. Whereas at peak power (for similar short bursts, admittedly) you're drawing up to 700A.
I think you'd want a massive truck alternator! I've been looking at camping electrical stuff - also DC. My Engel Fridge draws 2.5-3A average. I've got a mate with a house fridge off an invertor - it's drawing about 12A @ 12V. 700A at 156V? They are some really, really big numbers.
Also, alternators are designed to work best within a set rev range. With an IC Engine you're not really charging your battery until you're at 1500rpm, hit peak charge by 2000, and charge can drop off from 3-4000rpm... An alternator would benefit more from the gearbox - especially a (pulley) CVT - than the motor would! Without the right (variable) gearing, the effect of the alternator(s) on braking would vary from being very useful at middle speeds to being useless at low (town) speeds. You'd at least need to gear the alternator to spin faster than road speed - even with their tiny tyres, Mini road wheels are only doing about 1090rpm at 100km/h. You want 4360rpm at 100km/h (I'm keeping the maths simple - and providing useful braking below 100km/h)? That still means you're under the alternator's preferred rev range at 34km/h... You really would want a variable gearbox on it.
So, between the low output of alternators and rev range restrictions compared to the main motor, you can see it's preferable to use the main motor as the charger, which, as mentioned above, isn't the done thing with DC motors. I don't mean to say that a separate alternator/generator/regenerative charger system cannot or should not be done (on a DC system), I'm just saying I can understand why it may not be done!
Phill, I'm also curious - how do you work out your projected range? What's the theory behind it? I'm just wondering - there'd be a few rules of thumb in there, I'd guess? Otherwise it could get pretty complicated - factoring in mass, wind resistance, rolling resistance, percentage of time spent accelerating/decelerating/maintaining a speed, average speed maintained...
It'll be interesting to see how your projected range and your actual range compare.
And what percentage discharged are the batteries at the projected range? With my camping research, I've looked at deep cycle batteries , and all the caravaning/camping guys say not to discharge them below 50%, otherwise you dramatically reduce their service life. And obviously, the further into the range you discharge (drive) them, the lower the performance. I'm guessing that the batteries you're using are something in between a deep cycle and a car battery (given you've quoted both CCA and Amp Hours), so I don't know what the rule is with them. What's all the theory behind this part..?
Finally, is there anyone out there with anything like as quick an EV in Australia? I noticed a guy in WA building a quick MX5, but in my recent browsing of this subject I didn't notice many quick cars. Most were being built purely as money saving transport (things whose only purpose is to get you from A to B), rather than as true alternative (if shorter range) cars (things that you want to drive, that handle, etc). If I were ever to change over, I wouldn't want to sacrifice performance. I'd be like you - biggest engine you can fit!
If you don't post again soon, I can understand - if I were you, with the car looking so close to the road, I don't think I'd be able to stay away from the it!
But I'm looking forward to seeing your results.