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...I think I found a reasonable solution by placing a relay between the aux components (dumb shit I'll add in the future), and the rest of the car. This way the unimportant heavy-hitters will never be able to draw from the battery directly, and will only power on with the DC/DC converter.

...

Right, but once that relay closes (when the DC-DC provides power) it will stay on (maintained by the 12 V battery) even after the DC-DC goes off. You could put an isolation diode between the DC-DC output and the aux fusebox, powering the relay coil from the DC-DC side of the diode (so it would no longer get power when the DC-DC is turned off) but that would mean a diode-drop voltage loss for all DC-DC output (which you could adjust for to get the desired voltage downstream of the diode, but it would still waste power).
 

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Discussion Starter · #182 ·
Ah schnikeys! Nice catch.

I think this suggests that maybe a small powersports battery would be a better way to go. This complexity doesn't seem worth saving 5-10 pounds.
 

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Discussion Starter · #183 ·
DC/DC is in and running! I went with a 2.2kW Delphi that puts out 175A at 12.5V. Way overkill for my needs, but it works with my "empty" pack of 216V, was trivial to plumb for coolant, and the Volt converter was proving hard to find...Wiring was real easy, too: ignition, CAN (to Thunderstruck's CAN Translator), and power/ground.

I modified the left motor mounts to support a powersports-sized battery I had lying around...It's a pretty weak AGM battery, but it doesn't really need to do much anymore...I put it behind a 30A fuse...If it blows regularly, I'll set up some kind of contactor/solonoid/relay to separate it from the higher-draw stuff in the system...or maybe I'll just let it deal with the load until it can't...I just don't think it'll be a problem, and I don't want to go through the hassle yet. I strapped it in with tie-down. It ain't movin' much.

The converter is attached with two bolts to some janky little 1/8" brackets I fabbed up, bolted to the inverter. I was attempting to put more weight towards the front left. I was afraid it might wobble, but even with just two bolts in the center, it is rigid.

It's working well, and now my range isn't limited by my 12V battery and the headlights are actually useful! Next big thing is gonna be installing a relay/fusebox and cleaning up the rats nest of wires I created...



 

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Discussion Starter · #184 ·
Random anecdotal data:

One of the coolant hoses popped off while I was driving around, and I didn't notice until I was home. Temps never really spiked, and I wasn't being particularly gentle. Maybe I was getting bad readings from the sensors with no liquid in there, but I dunno. Everything ran fine...Hopefully I didn't fry anything!

These things just don't seem to produce much heat, though I'll have a much better idea when I test out higher sustained speeds. I keep forgetting that a full throttle burst isn't as much of a strain to the electronics as five minutes on the highway.
 

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Discussion Starter · #185 ·
Random axle notes: As I was standing underneath the car, it occurred to me that a much better way to measure lateral positioning of the motor is with the Leaf axle stubs in. It's a shorter distance from the subframe that way, and the measuring "surfaces" are identical on both sides. For the anyone else who's doing a Leaf-in-Mini, I guess...
 

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Wow!
What a read, it's taken a while to catch up but the work you've done is going to save many people, including me a LOT of time and money.
Thank you so much.
Out of curiousity why didn't you weld the mini shafts to the leaf shafts at the correct length then send them off to be copied?
I can't wait to find out your range and how you finalise your battery packs.

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Discussion Starter · #187 ·
Out of curiousity why didn't you weld the mini shafts to the leaf shafts at the correct length then send them off to be copied?
Intimidation, perhaps. I lack the talent and tools to accurately machine a Leaf axle so that a Mini axle will slide into it. The idea of just kind of welding them end-to-end for the purpose of measurement simply never occurred to me!

Another bit is that I literally don't know how long axles are supposed to be. They need lateral play to work with the moving suspension, but how much? I can surmise that getting the inner tripod joints in the "middle" of the stub is the goal, but I never really got that far. From full droop to standard ride height, the Mini doesn't have much of a length change with the Leaf motor in here. In the end, I just did what The Drvieshaft Shop told me to.

The first shafts I got were 13.5" and they measured an inch too short based on their criteria. I swapped them for 14.5" shafts, and these seem too long...maybe by an inch. I can't explain the discrepancy, but there is at least some play in these, whereas the 13.5" shafts seemed pulled tight, always. Either the Mini is unique, the Mini/Leaf combo is unique, they're telling me how to measure incorrectly, or I'm just measuring incorrectly. I dunno! These measurements might not translate to any other shafts besides the one they make. They work well now with no weird noises, so I'm inclined not to mess with anything unless a problem presents itself.

With regard to range, I'm getting 6-8mi/kWh (~60-80mi in reality), but average speed is something like 20-30mph. Low speeds, but lots of full-throttle and steep hills and what not. It might very well be half that at 75mph. I don't think I'll have a great idea until I can just...drive in a straight line for a while. I also don't quite no how low a voltage I can hit due to sag. The car seems to use much less energy towards the high end of a charge than the low. I don't have a great idea about it yet.

My plan for the batteries is to put in as many in as I can stand...These cars were designed with two rear passengers in mind, but my weight distribution is different, so I don't fully understand the implications yet. Maybe some red dot or Smootha-Ride cones up front, and stiffer yellow-dot cones in the rear? I'm tempted to reinforce the body and install coilovers for adjustability, but that raises a fervor on the UK Mini forums...At the very least, the area right behind the seats is really only 2/3 towards the rear, and everything is between the axles.
 

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Discussion Starter · #188 ·
Shit. When I swapped the 13.5" axles out, I should have pulled the boot and just...looked at where the tripod bearings were in the housing. OH WELL
 

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That's great info thanks, I'm currently looking at battery location, after watching some vids on the Swind e mini you can see they have raised the rear seat and tunnel so I'm looking at modding these areas to squeeze some batteries in. Would you mind confirming the size of each module for me please? I want to take into account the joining plates too. I'm sure I can get 6 in the tunnel space but would like to squeeze 9 in if I can.

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With regard to range, I'm getting 6-8mi/kWh (~60-80mi in reality), but average speed is something like 20-30mph. Low speeds, but lots of full-throttle and steep hills and what not. It might very well be half that at 75mph. I don't think I'll have a great idea until I can just...drive in a straight line for a while. I also don't quite no how low a voltage I can hit due to sag. The car seems to use much less energy towards the high end of a charge than the low. I don't have a great idea about it yet. (Sorry,this should have been quoted)

I have an i3 and the efficiency definitely decreases in line with charge, I seem to be able to go to the next town from 100 to 95 percent but not the return when on about 10 percent.
Just think of a cordless drill slowing down as the battery dies.

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Discussion Starter · #191 ·
This post has some to-scale configurations I was thinking about:


Leaf module dimensions are easily found. They may differ slightly from year to year.
 

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Discussion Starter · #192 · (Edited)
Some progress on these batteries. With the car as it sat, the corner weights were as follows (in pounds):

425 470
380 325
Front 895 (56%)
Rear 705 (44%)
Total 1,600

Better than I expected, reallynot much more than stock, with better distribution. Adding the remaining 18 modules would add another 150lb, and even if they were added directly over the rear axle, I'd still be at 51/49, with a rear weight roughly equivalent to two adult passengers, which the car was (somewhat) designed for. I don't have final weights yet, but I expect that probably only 50-100 of the 200 or so added will be on the rear, as most of the weight will be about a 1/3 of the way forward to the front axles. I figure I'll just put all 48 modules in there and see where I land!

After staring at numerous layouts in Sketchup (and even building a frame for one), I settled on a fairly simple set of stacks bolted through the floor (which required cutting out the shelf for the rear seat). The six modules in the rear seem like maybe they aren't worth the extra hassle, weight, and clearance issues, but...I've done the work, so I'm gonna see what everything weighs before changing much.



Despite measuring everything three times and doing 3D mockups...the real world is analog and messy, and I lost count of how many times I've pulled batteries in and out of place...Best-guess fabrication, corrected by doing it again and again...The plates are 1/8" 6061 aluminum and the rods are 1/4" stainless steel.

The seat doesn't have enough room behind it for my likes...It would be nice to have the option of moving the seat back further in the future, and I do still plan to cover all these things in a nice interior-looking box of some kind...
There might be room for more modules under the seat, but I'd have to modify the hold-down bracket, and up front they kinda hit my ankles a bit...I'm just a bit worn out and I want the car back on the road.

The batteries are bolted tight, and they don't move at all when I try and shove them out of place.























 

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Wow!
That's a LOT of batteries!!!
How the hell do they get the batteries in a Swind e mini and still have space?
I must admit to having doubts about using a Leaf because of the shape of the batteries, I'm going to do some cardboard mock ups of i3 and Zoe batteries to see if they fit in easier

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Discussion Starter · #194 · (Edited)
I believe Swindon either removes the transmission tunnel or puts modules on top, in a kind of T formation (with the top of the T being under the rear seats). I believe they make the seats narrower or shift them as well.

 

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That's what I'm looking at doing, still think the Zoe modules will be a better fit but hope to find out soon

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I believe Swindon either removes the transmission tunnel or puts modules on top, in a kind of T formation (with the top of the T being under the rear seats). I believe they make the seats narrower or shift them as well.

Anyone willing to change the floor of the vehicle that much might consider making it fit a Chevrolet Volt pack, in its complete original form. In the Volt the lateral part runs under the front part of the rear seats, and the rest runs up the tunnel. For a two-seater (not stock Mini configuration), the lateral part could be immediately behind the seats, leaving the rest running up to under the dash. You need to be willing to tolerate very narrow seats if you do this in as narrow a car as a Mini.
 

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As Tremelune has pointed out the Swind-E mini has a complete new floor / exhaust tunnel to accommodate a T shape battery pack which spans from the front bulkhead to the rear heelboard.
Trouble is with this option is you are modifying the chassis which is an instant IVA in the UK, if you are willing to take the risk and the cost of doing it then fair play.

With all the conversions ive seen so far, its either lose the rear seat or the boot to get the batteries in.
I think we are still a few years off having anything small and power dense enough to not go with this option?
 

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This is one helluva thread and build, amazing work from scratch!
So now oyu've got the full 48(?) modules in, whats your weight distribution like?
 

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As Tremelune has pointed out the Swind-E mini has a complete new floor / exhaust tunnel to accommodate a T shape battery pack which spans from the front bulkhead to the rear heelboard.
Trouble is with this option is you are modifying the chassis which is an instant IVA in the UK, if you are willing to take the risk and the cost of doing it then fair play.

With all the conversions ive seen so far, its either lose the rear seat or the boot to get the batteries in.
I think we are still a few years off having anything small and power dense enough to not go with this option?
Good to know, thanks

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Discussion Starter · #200 ·
Well that didn't work out. It seems I did not take BMS and HV wiring into account enough when designing the battery pack...I had great weight distribution (though unmeasured) and a low center of gravity, but I also spent painstaking hours putting it together, in order to avoid electrocution and fires. Even so, the clearances were just too tight and the wiring too messy to be certain about. Sparks flew on several occasions, and (despite testing before plugging the BMS wires in), I think I fried a circuit or two, and I managed to weld my contactors closed at some point, though I never really figured out how.

I took everything out. Back to the drawing board. It was...painful.

I would have had a much greater chance of success had I kept the BMS wiring in the Nissan harnesses and modified them to fit instead of rolling my own...I thought it would be easier, but alas! I then decided that doing it in the car would be less effort than mocking it up inside first, and then transporting everything...There was some logic there: the Mini is tight tight, and the only way to be sure is to do it in the real space...Unfortunately, it was very hot that week, and I got lazy and impatient, and it shows. Just need to source some long Leaf busbars...

This time around I can do all the design and wiring inside. I'm leaning towards much greater simplicity with this next iteration, as well as way more room to move the seat and build a sort of platform/enclosure. The modules under the seat just weren't worth it, especially considering that the charger and an audio amp will fit there nicely.

I'm gonna aim for 44 modules (370lb), and if it seems too tall, go for 36 (300lb). The colored circles are BMS groups (Thunderstruck divides them into 12-cell groups, and they shouldn't span a fuse or disconnect).







 
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