Chicago-E
Well-Known Member
- First Name
- Brad
- Joined
- Dec 9, 2021
- Threads
- 7
- Messages
- 153
- Reaction score
- 194
- Location
- Chicago
- Vehicles
- 2021 GTPE Iconic Silver, 2021 GTPE Space White
- Occupation
- Generator Technician
300 per battery at 50000 units is 15mil. not chump change. all those inefficiencies add up to big dollars. I expect things to be better with the 2nd gen and plan on grabbing one when they are released.Let me try to break down each of his claims:
Yes it could be reduced with greater use of CAN bus, but I don't think it's that excessive now. That would be the theoretical maximum savings. All of the modules and body features need to be connected. The legacy modules used would need to be hooked up like they are now. Moving to a completely integrated CPU that controls all functions like Tesla is probably in the future, but there is a high engineering and time cost to get there. Purpose-built EV modules will come that will simply things. As has been said, the engineers had to take existing off-the-shelf modules used in other vehicles and make them work together in order to save time. As a result the Mach-E has a lot of modules that are coordinated to work together in some unconventional ways.
In theory that sounds like the maximum weight savings from eliminating the 1.6 km of wire, which won't have that big of an impact on range. The copper cost would likely comprise most of the $300. But I wonder why he said "battery" instead of "vehicle"? Perhaps he's referring to all the the BMS wiring in the pack. Each cell has a wire to the BECM (94x) for monitoring and balancing, a dozen wires to the HVBJB for controls, plus ten thermistors. As a result the BECM has about 140 wires going to it. Rather than being centralized with individual wires, the design could be decentralized to be a circuit board on each individual cell module that handles all those functions, and communicates back to the main BECM with a LIN bus. That could eliminate about 120 wires. Tesla uses a decentralized BMS like this in their packs.
This one is difficult to decipher. He must be taking about regenerative braking. The Mach-E seems to top out around 100 kW of regenerative braking for a very short time, which is a decent amount (Model Y is 85 kW I think, but the pack is proportionally smaller). But I personally think he's talking more about the issues seen with long-duration regen going down hills causing the motor inverters and battery pack to overheat. When he says battery size, I actually think he's referring to the busbar size in the battery pack or the amperage limits on the cells themselves. I've written about this previously, but it's my opinion that the busbars and connections were designed too small inside the pack.
The busbars should have been made thicker (5mm instead of 3 mm) or wider to handle the peak current demands better without overheating. They are big enough if you are driving a constant speed on flat terrain, but lots of acceleration or going up mountains can easily overheat things. The internals just weren't made robust enough. It's also my view that the pack design predates the decision to make it a performance oriented vehicle, rather I think the pack was designed for a "compliance car" which would have limited acceleration (possibly RWD only). The creation of the GT models with dual large motors really put demands on the pack it wasn't ever designed for, hence the 5 second rule. The thin busbar also puts more stress on the high voltage contactors in the HVBJB, making them more likely to fail due to insufficient heat sinking.
In summary, there are certainly greater efficiencies that can be made with the Mach-E's design. But I think the savings numbers he's giving to investors are absolutely top end. I don't think he will be able to save as much as he tells investors without sacrificing the quality or features of the product further. The focus should be on increasing simplicity AND quality because the warranty costs are astronomical.
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