Vibration Isolation for Battery Box EV Conversion

869 Views 10 Replies 6 Participants Last post by kennybobby, 4 mo ago

connor016

Discussion Starter · 4 mo ago

I am currently building two steel battery boxes that will house 2 modules from a Tesla Model 3 (2 per battery box stacked, supported from the side as intended). This will be going in a 4x4 and may see some off-road use but likely minimal, just typical road conditions. It will be mounted to keep a low CG to the frame so it will be on the sprung side. To me it still seems like you would want to put some sort of vibration isolation but I don't believe Teslas have any. Does anyone have any recommendations here?

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remy_martian

· #5 · 4 mo ago

Tesla's Model S and Model X modules are mounted on garolite ears, which would act as a mass-damped spring suspension, so don't say they don't have it when they actually do at the module level....

As far as Model 3 goes, I'm not familiar with how those mount to the box.

If you use the factory mounting scheme, in other words, you should be OK.

Unlike a FLA, there's no plate material to shed to the bottom of the battery which creates electrical leakage.

The S and X have a lot of suspension travel which is increased with changing the ride height to max. Air ride is as good as it gets. Again, know nothing about Model 3.

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remy_martian

· #7 · 4 mo ago (Edited)

Most "offroad" is 5mph crawling stuff, so unless you're talking Baja or Dakaar racing stuff, I just don't see how that's more grueling than running a road car down a rural dirt road with its potholes and washboard (washboard and Belgian Brick are standard chassis qual tests by OEMs, so Tesla's module mounts should have that covered).

The bigger concern here, in my mind, would not be vibration isolation, but articulation and chassis twist. I can't think of an OEM box where the modules would survive the chassis twist we see in rock crawling. If that is the long pole in the tent, the box needs to be hinged and constrained in a manner to allow massive frame flex while the box remains torsionally stiff and undistorted. Can be done, but will take up a lot of volume in the free space needed to accommodate the two - frame twist and a rigid box.

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remy_martian

· #9 · 4 mo ago

Correct. And if you watch the Rivians offroading, they lift wheels, despite extended suspension travel to try to compemsate, instead of maintaining ground contact with all four by flexing the frame in combination with articulating the suspension.

In an EV, the battery box cannot flex in torsion, though modules do make for less damage in torsion than a "structural battery" would....which is why they need a massive diecasting.

GM's bloated abomination is a car, not a truck, imo -- a four ton unibodied Honda Ridgeline.

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