need guidance in vibration proofing

[bronz]

Hello E-S

I am building an e-bike out of necessity due to some rather unfortunate events, and I am pretty sure that the only frame I will have at my disposal will not have a lot of shock absorbing capability. As far as I know there are only two components which are really vulnerable to vibration damage, the battery pack and controller. My plan for the battery pack is to suspend the cells in a high density polyethylene frame sort of like this:

I will be using Headways as well. This arrangement eliminates the possibility that the cells will rub together and wear through the polymer coating, causing a short. I also plan on fixing all the sense wires in place so that they never rub against each other or the cells. If there is anything more I could do for the integrity of the pack then I would like to know what. I have no idea how to make the controller ready for vibration. I have heard of caps coming off completely and stuff like that and I don't know how I can prevent that. Also, I would like to know if BMS' like this one tend to fail because of vibration, and if so what I can do about it.

http://www.bestechpower.com/64v20spcmbmspcbforlifepo4batterypack/PCB-D166.html

Thanks 8)

 

[Drunkskunk]

Vibration really isn't a problem at bicycle speeds. Just make sure everything is mounted securely and you won't have a problem when the bike is used as a bike.

The best solution for cushioning the ride of a normal bicycle is balloon tires. Anything above 2.35" is going to ride much smoother than a normal bike tire.

 

[dogman dan]

That looks good to me. It looks like the plastic will support the cells by the cans, rather than by the terminals.

Sometimes things will get some damage from extreme vibration, but I have had the bikes shake to pieces before anything else got to be a problem. Controllers are pretty good, but I've had all the bolts vibrate out of hubmotor covers on an extreme ride, along with other parts of the bike falling off.

The one thing that is typically vulnerable to vibration damage is chargers. So don't make it a permanent part of the bike.

 

[r3volved]

Looks like a good setup! I like that battery design.
The controllers are actually very resilient. They're often mounted below the down tube and often exposed to the worst of the elements. I layered a piece of foam between my controller and down tube...this is my second controller with no issues (first one still works fine just upgraded for more current).
I did the same with the batteries...anywhere they contact the frame, there's a layer of foam between. Zero issues driving through trails, small jumps, across icy/bumpy/slippy roads and sidewalks.

As long as it's secured to the frame solid, you won't get any more vibration than the frame itself.

 

[spinningmagnets]

Chargers could be made to be made to be vibration-proof, but customers aren't spending more for that feature or demanding it, so companies aren't making them with that capability. As it is right now, every few months someone joins ES and wants to carry a charger with them, and it quickly dies.

The controllers are a different story. Although some are better at it than others, they are designed from the beginning to be ridden on a bicycle, and controllers that are especially fragile will quickly get a bad reputation. If you want to add an extra measure of vibration-resistance, you can buy or make a suspended base for it. Just scale up the well-researched designs being used for RC helicopters. Tips for that can be found here:

http://copter.ardupilot.com/wiki/vibration-damping/

Where is the battery pic from? Looks awesome, and I need to know!

 

[bronz]

Thanks for taking the time to answer my questions, I really appreciate it. I no doubt would have mounted my charger on my bike if I had not asked about vibration proofing. That will save me a lot of frustration.

Where is the battery pic from? Looks awesome, and I need to know!

That picture was taken from the SplinterOz'sc thread in the motorcycles/scooters section. He also used it as an example of how he wanted to design his battery pack and the results were so good that I decided to do the same thing. He ended up using high density polyethylene instead of what I assume is polycarbonate in the picture, which I feel like is a good choice. HDPE is probably a lot cheaper and easier to work with but is still very strong.

http://endless-sphere.com/forums/viewtopic.php?f=10&t=25697&start=75#p394790

 

[liveforphysics]

Nothing is vibration 'proof', water 'proof' or even particle ingress 'proof', temperature 'proof', pressure 'proof' etc.

Things can only be resistant.

Look for any place you have different potentials in close proximity and add insulation of a type that doesn't slide/chafe. Throwing in a fuse or two in or at the pack itself is a good idea as well.

 

[Punx0r]

I would look at using some little rubber mountings for the bolt holes on your battery. I've seen some that are like minature engine mounts, with a little M6 thread each end and a 3/4" dia. 1/2" long piece of rubber between. It's high frequency vibration that causes mechanical/electrical things problems, as even low G causes fatigue and fracture. Higher frequencies are much easier to damp out. Low frequency is hard to damp, but the human rider will usually give out first - a handful of G is nothing to most inanimate objects, but quite uncomfortable to a person.

Things that can wobble about in response to vibration are prone to failure. Hence you see goop sticking large electrolytic capacitors in place on controllers, so they don't fatigue their legs. If everything is held firmly in place it will be ok