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?
Vibration Isolation for Battery Box EV Conversion
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Could be over thinking this. All the FLA batteries I have ever seen are hard mounted and then Volt lipos are also. I believe if you are bouncing around enough to bugger up a battery you have human body problems getting ready to occur. You do want them to not move in whatever they are packed into.
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Sounds like a good idea, may be difficult to implement.
Maybe invest in the vehicle suspension to have adequate stroke for the dampers to work along with the necessary spring stiffness for the load and the expected conditions.
If you put springs on the batteries, then they are floating and have some unconstrained degrees of freedom. (unless you put them in 3 axes +/- directions)
If you use some elastomer bushing or damping foam (sorbathane), then it must be held in a preloaded condition, e.g. 90% compressed, in order to be in the effective zone, and the stroke is very limited. Also would need in 3 axes, +/- directions.
An engineered $olution is likely possible, but the requirements would need to be well defined, e.g. mass, disturbance force vectors and frequency, shock load, required frequency response.
Maybe there could be a solution short of the full-blown aids, but sounds like a moving target.
Maybe invest in the vehicle suspension to have adequate stroke for the dampers to work along with the necessary spring stiffness for the load and the expected conditions.
If you put springs on the batteries, then they are floating and have some unconstrained degrees of freedom. (unless you put them in 3 axes +/- directions)
If you use some elastomer bushing or damping foam (sorbathane), then it must be held in a preloaded condition, e.g. 90% compressed, in order to be in the effective zone, and the stroke is very limited. Also would need in 3 axes, +/- directions.
An engineered $olution is likely possible, but the requirements would need to be well defined, e.g. mass, disturbance force vectors and frequency, shock load, required frequency response.
Maybe there could be a solution short of the full-blown aids, but sounds like a moving target.
Yeah probably overthinking this if Tesla doesn't have any additional vibration isolation. I would imagine a pothole/square edge bumps are fairly harsh in a Tesla given the limited suspension travel so the modules themselves must be designed to withstand that. I have designed vibration isolation systems and dampers which is why I was thinking it would be a good idea. Initially I was thinking just to mount 4 vibration isolators with studs but packaging the battery packs is a huge challenge with very little clearance so between frame flex/isolator deflection it might end up causing more problems with potential interference if it isn't needed.
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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.
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.
Yep not sure about the S/X as I am using Model 3 modules but they bolt directly to the battery enclosure and also have flanges that clamp to the enclosure with no other isolation material. They are only supported on the sides. Maybe there is something internal or the foam they use around the cells acts as a vibration isolation. I will likely want the battery box to be removable so I am thinking I will still use some type of vibration isolating mounts since it will still be used off-road occasionally.
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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.
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.
The only EV battery enclosure which I have heard of with an isolated mounting system is the one in the Ford F-150 Lightning... and that may be as much for torsional isolation (to handle frame flex) as any other reason. GM is not isolating the battery in their EV trucks (which have what is probably a stiffer frame), Rivian is not isolating the battery in their truck (which has a frame which is stiffened by the body), and Ford itself doesn't do isolate the battery in the any other model (including the E-Transit).
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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.
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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If you're looking to add vibration isolation to your battery boxes for a Tesla Model 3, you have a few options to consider.
- Mounting Material: You can use a rubber or foam mounting material between the battery box and the frame to absorb any vibrations from road conditions.
- Stiffening the Box: If you make the box stiffer, it will reduce the amount of vibration that gets transferred to the batteries. You can consider adding reinforcement to the walls or using a thicker gauge of steel.
- Vibration Dampers: You can also add vibration dampers directly to the battery modules to help isolate them from road vibrations. There are many commercial products available that can be used for this purpose.
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Sounds like ChadGtd talking..
Concerning #2, if you stiffen the box then wouldn't MORE shock and force gets transmitted to the cells, not less?
Concerning #2, if you stiffen the box then wouldn't MORE shock and force gets transmitted to the cells, not less?
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