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Discussion Starter #1 (Edited)
I have a couple of friends who are working on an LTO conversion, so I thought I'd post some layout work I've been doing. This particular layout is for a plywood baseplate that can easily be made up in a day. Mounting of components and wiring will obviously take longer. Major components will need to fastened securely to the baseplate. Atheos used T-Nut fasteners, such as these:

https://www.lowes.com/pl/Tee-nuts-Nuts-Fasteners-Hardware/4294546123

to attach his battery packs to his plywood baseplate.

Though I have use pine plywood for this layout, I did a bit of shopping at Lowes when I bought the 2"x2" piece for $5.99. It appears to me that poplar and birch plywood both have tighter grain and are probably better. If I were going to install a plywood base, I think I would invest the few extra dollars.

Below, I show a rough sketch, with accurate dimensions for how the baseplate is to be shaped. The builder will want to pay close attention to any minor trimming or shaping so that the baseplate can fit reasonably easily into the IPU compartment.

As a finishing step, I would apply a couple of coats of good marine varnish, or urethane just in case there is a leak, or for some reason the plywood gets wet. One might also consider marine grade plywood which uses a different glue between plys.

For this configuration, the BCM and MCM are sandwiched together and mounted on edge with the lower tabs passing through a hole to a mounting bracket. Pictures will make that clearer.
 

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Discussion Starter #2
Below is the detail of the BCM/MCM mounting bracket, which is constructed with a length of 1X1" aluminum angle. The bracket is extended well forward and well beyond the pass through hole to help strengthen the plywood in the cut-out area.
 

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great information Jim. Do these measurements allow for a flat area or does it have a slope? What about the 18" dimension to accommodate not bending the right side flange of the IPU box
 

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Discussion Starter #4 (Edited)
Topside Pix of BCM/MCM Mounting

This shows how the BCM/MCM sandwich is positioned on the topside of the plate. Don't start fabricating yet. There is a small problem to resolve ;-)
 

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Discussion Starter #5
great information Jim. Do these measurements allow for a flat area or does it have a slope? What about the 18" dimension to accommodate not bending the right side flange of the IPU box
The mounting plate will be sloped by some degree. I currently have7/8 inch spacers under the plate which lowers slope to a small amount, but still sloped. As we will see later, some slope is necessary to make the edgewise BCM/MCM sandwich fit under the IPU cover. Still working a clearance problem with the front tabs of the BCM/MCM. It is solvable by several different methods.

The 1" notch in the right side of the plate is necessary to allow installation of the plate without having to bend up the IPU flanges and break the corner spot weld - which I did on my own installation.

Stopping for the tonight. More tomorrow.
 

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Thanks, Jim!

Sam
 

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Discussion Starter #9
Overall Layout

This pix is my vision of the overall layout of Layout #2. Just to dispense with one question right away - why not put two packs in front to have better weight distribution in the car?

The problem is with the large battery hookup bundle in the top left of the picture. If two batteries go to front, then the only space for the vertical BCM/MCM sandwich is to the rear. In that position, the wiring within the battery bundle will not reach the BCM/MCM. Extending the wires would be a large effort since there are so many.

I have been running this exact weight distribution in my own car for 4 months now. There may be a very slight difference in handling balance (i.e. overstear/understear), but it is hardly noticeable if at all. In any case, the total weight of the conversion is about 30-35 pounds heavier, so the exact location, within this small area, isn't likely to matter.
 

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Discussion Starter #10
Cable Layout

This pix shows how the cables are to be routed for Layout #2. There are several options for which battery to split so that the 6 subpacks are equally split with respect to the junction board switch - which I view as desirable. I have chosen to split the left rear pack lookng forward from the hatch. This arrangement seems to result in relatively equal length cables. I could find no other arrangement which did so.

I have attached temporary tags on the important cables so that their function can be identified. Just as a small convention which I adopted, the low side cables, with respect to the switch, are black. The high side cables are red.

Since my own configuration has the BCM/MCM underneath the plate, they do not show in this pix.

I believe that this is the easiest configuration to build, but the one constraint is that you will be forced to use IMAC&C rather than any MIMA you might own. There just isn't room for the MIMA P&P adapters and the comms cable hard end. Most folks are probably going to want to use IMAC&C anyway and it certainly gets good reviews.
 

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Discussion Starter #11
IPU Cover Clearance Issue

Default IPU Cover Clearance Issue
I promised yesterday to show the one problem which this configuration encounters. Please study the below pix. The board at top is a straight edge laid across the mounting flanges of the IPU. It can be seen that currently the front tabs are a few fractions too high.

There are several measures to make room for the cover.

1. First, the sandwich can be lowered slightly by relieving the MCM plug clearance in the front(pix to follow). Second, a clearance hole can be cut in the IPU cover, and the tab can be shortened to a minimum by filing off some material.

2. A better solution IMO is to remove the front tabs on the BCM/MCM. These aren't very heavy units and they don't require a lot of mounting strength. The bracket that they are attached to is probably adequate, but I think a brace to the rear top tabs would be worthwhile.
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Discussion Starter #12
I have discovered a third configuration. Like all the configurations, there are advantages and disadvantages.

I previously made the statement that two of the three packs had to be toward the rear because of the length of the main IMA wiring harness. I have discovered that, if one is willing to lengthen 15 wires, then the harness would reach a rearward positioned BCM/MCM sandwich.

The wires requiring extension are in the BCM A plug wiring, a small "spur" off the main IMA harness. This plug carries several signals which might be sensitive to electro-magnetic interference caused by large current changes in the 4AWG main series power cabling. The signal wire bundle will necessarily be in very close proximity to the main power cables, in several instances. The BATTSC11 AND BATTSC12 serial comms wires to the ECM are in this bundle.

I note that the stock battery configuration does not create these interference conditions. In the stock configuration, the main power cable are quite remote from the various signal wires. I think Peter might have to render an opinion on this situation. I have reservations, but no real experience in the area. It seems to me a lot of risk for a small gain.
 

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I would avoid running ima signal wires near the high current ima motor wires or battery power cables if at all possible.
It's not good practise and might lead to interference issues.

Can the BCM/MCM go behind the seats panel?
 

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Odd question: how about shimming the height of the ipu box with wood shims to a desired height ? 1/2 ", 3/4", 1" ? Moving the ipu cover high enough to allow mounting the bcm / mcm on top of the pack and simplifying cable and plug arrangements.

In the pic I have layed some random wood scraps at the front and one side, with arrows to indicate fastening points for the shims which would really go around the whole works. It shouldn't take much to hold the shims in place.

All the remaining fastening points could be for the ipu cover using longer 6mm bolts.
 

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Discussion Starter #15
Odd question: how about shimming the height of the ipu box with wood shims to a desired height ? 1/2 ", 3/4", 1" ? Moving the ipu cover high enough to allow mounting the bcm / mcm on top of the pack and simplifying cable and plug arrangements.
That would leave you with a very unlevel hatch floor, plus you would not be able to attach the rear vertical part without some other additional steps.

I think we willfind a way to avoid that extreme.
 

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Discussion Starter #16
Can the BCM/MCM go behind the seats panel?
I played around a bit with the parts. I think that it is possible to mount the BCM and MCM, separated by a bit, in that area. Nothing is going to be perfect and that approach isn't either. A special hand fabricated bracket would be needed, and it would have to be epoxied at the bottom, since the horizontal surface is immediately over the gas tank.

By doing this one would have to remove all the tape and wire loom from the main IMA wiring harness and lay out the wires a bit differently. Might not require any wire extension.

Pix later.
 

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I would say you need to retain relatively easy access to the BCM/MCM, especially if later you will be using a BCM replacer or others mods..

Then at least you can access them without taking out the entire battery.
In the stock configuration all the electronics is pretty easy to access.

I like MD's shimming idea to keep the bcm/mcm in stock position.
 

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Thank you!

I have not done much with the IMA batteries, other than to quit banging my head against the wall trying to resuscitate old sticks.

This is interesting.

Just my 0.02 worth,
Tim
 

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Discussion Starter #20 (Edited)
I would say you need to retain relatively easy access to the BCM/MCM, especially if later you will be using a BCM replacer or others mods..
Yes, certainly. That is the reason I continue to work on the mechanical part of the layout so that it can be improved. Though I have configuration #1(config.1), BCM/MCM under plate, that is far from perfect in a troubleshooting sense. In fact, it is nearly impossible with config.1 to do powered up troubleshooting.

<snip>

I like MD's shimming idea to keep the bcm/mcm in stock position.
Though the MD proposal solves the access problem, on the fact of it, it retains much of the risk of having signal wiring in very close proximity to high current power wiring; and there is risk of having the metallic cases of the BCM/MCM short out the battery and create a fire hazard. This could possibly be mitigated by using a thin plate consisting of an insulator on bottom and a thin sheet of aluminum on top, to which the BCM and MCM are attached.

Later: I also note that the packs aren't uniform in their mechanical configuration. Some packs have a long stud which project much higher than the other terminals. This will complicate matters is an insulating plate is installed on top of the battery terminals.

I do note that the slight raising of the hatch platform with the MD suggestion could be mitigated by using styrofoam sheet to re-level the platform along the side and back of the IPU.

No perfect solution yet:confused:
 
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