Battery Restraints

[Logan Pace]

Hello all,
Our Formula Electric team is trying to find the best way to restrain our batteries in the car this year. If you aren't familiar with the rules, we have to restrain them to sustain a 10 G vertical and 20 G lateral load. We have the lateral taken care of, but the vertical is giving us some trouble.


So far on the table we have:
Double sided sticky tape (not our first option, we have tensile test data proving it works)

Industrial strength zip ties (150lb tensile strength, we could use a few of them)

Heavy duty straps similar to backpack style.

We can't really think of anything else, however we are trying to use the least janky option we can find.

Thanks for any help!

[mech5496]

Sticky tape and zipties?! Really?

Take a look on FSE website, find team presentations on the subject, download and take a look at them.

[MCoach]

http://www.yorkshirelaser.co.u.../afm_ep_14_large.jpg (http://www.yorkshirelaser.co.uk/interface/fabrication/afm_ep_14_large.jpg)

Why not bolt down something like that?

[Dash]

pop the hood on your car and see how they do it. Most cars have a small metal strap thats bolted down to the frame.

[Paul Achard]

mech5496, do you have a link to the presentations you mentioned? A quick look around the FSE site revealed nothing...

[mech5496]

It is on the academy section under workshops, with tons of other interezting presentations, but you need to login to have access

[TMichaels]

Harry is referring to this part of our website:
http://www.formulastudent.de/academy/workshops/

After login you have access to all the slides of all FSG workshops that have been conducted so far. You may choose the respective workshop on the left menu.

[Paul Achard]

Thanks, that's quite useful!

[Michael Royce]

Logan,
Batteries, especially those in an FSAE electric car, need to be bolted down with metal brackets! Don't try zip ties or velcro. I will not even allow them for a light weight 12 volt battery in an IC engine car! For those, I will sometimes allow a 1 inch wide HD nylon strap with the appropriate buckle, but no zip ties or velcro. And you are talking about batteries that weight how much?!!

[MCoach]

Originally posted by Michael Royce:
Logan,
Batteries, especially those in an FSAE electric car, need to be bolted down with metal brackets! Don't try zip ties or velcro. I will not even allow them for a light weight 12 volt battery in an IC engine car! For those, I will sometimes allow a 1 inch wide HD nylon strap with the appropriate buckle, but no zip ties or velcro. And you are talking about batteries that weight how much?!!


How lightweight are we talking? Our team very graciously and easy passed with our velcroed down battery (IC car). Never mind the little bugger weighs about a pound.

The velcro also makes it easy to store other places:

The wall on the trailer
The ceiling above your best mate's bed
Underneath the table that everyone eats lunch at
The shelf of a cabinet for safe keeping
Inside the car
Anything that has a soft surface that you can reach!

For the much larger Electric car storage areas, I would still opt for something a little more positive locking.

[TMichaels]

Most of the teams take the regular approach and screw the accumulator container to the chassis.
Given the weight of the batteries, I doubt that our Scrutineers would let you pass with zip ties. You will probably already fail the ESF review with that solution.

[mech5496]

Tobias, I think he refers on mounting the cells inside the container...

[TMichaels]

Ah ok, my bad.

[Charles Kaneb]

May I suggest something simple, light, and cheap?

A seatbelt.

Attach it at one end. Run it through a series of D-rings that bring it below the level of each battery module so as to pull it down, then pull it tight with the buckle.

They're usually free at junkyards and good for a couple tons of total force (250 lb driver in a 25g impact!).