Tractive System Accumulator Container - Mechanical Configuration

[Sud600]

Hi

I am Sudharshan Iyengar from Team Ojas, India. Actually we were going through the 2015 rule book and a particular rule in the EV section caught our interest.
(rule 3.4.1 to be exact)

"All accumulator containers must lie within the Major Structure of the Frame"

as opposed to

"All accumulator containers must lie within the Frame" (a 2014 rule)

Last year we placed our battery packs in the side pods. So can we go with the same battery placement this year too i.e. place them in the side pods??

Any advice and assistance would be highly appreciated.

Thanks

[Adam Farabaugh]

My interpretation says the answer to your question is yes, as long as you satisfy EV3.4.4 as well.

I interpret the new language you called out to mean that the battery pack can no longer be behind the main hoop braces / main hoop brace supports, and cannot be too high above the main hoop brace supports or the side impact structure.

I do believe this means that you need to be very careful about the height of your packs - if they are above the side impact structure top member then you could have problems.

I'd be very interested to hear the answer to this if you ask the Rules committee.

[Sud600]

Hi Adam,

The definition of major structure according to T3.3 states that it comprises of the portion of the frame that lies in the envelope defined by primary structure, and nowhere it is
mentioned that the side pods comes under primary structure of the frame.

I am comfortable with the fact that my battery pack cannot be behind the main hoop braces and cannot be too high above the main hoop brace support or the SIS, but still not
sure about its placement in the side pods.

[SomeOldGuy]

If you have serious doubts about the legality of your design you will need to contact the rules committee. Nobody here has the ability to say your design is legal or not.

That being said my understanding of a legal configuration that places the accumulator in the sidepod involves:
-Make the sidepod your side impact structure
-Properly triangulate back to the roll hoops

[Adam Farabaugh]

If your sidepods are essentially a second layer of SIS, then you can call them your SIS, and then they are part of the primary structure.

[B757]

Has anyone heard back from the rules committee on this?

Also, to introduce myself, I'm James Wang, and I'm helping start a new electric team at Boston University. We're designing and building a car for the 2016 competitions, and I'm handling the battery pack design. Unfortunately, since we aren't registered for 2015, we've had a hard time reaching the rules committee. Our cells aren't very energy dense and we'll face difficulties fitting our cells into the back, so mounting our cells into sidepods would be preferable.

[Adam Farabaugh]

What kind of cells are you using? LiFePo or LiPo (or I guess others are possible)?
If you're starting out a year and a half ahead, I'd encourage you to go for the win! No reason to make a 10th, 5th, or even 2nd place car your goal.

Sidepods are legal. This info is not from the RC but from my better understanding after having gone through the AFR. This could be wrong but I'm pretty confident this is on track

If you are doing AFR for accumulator attachment, then there are two options:
- Two layers of SIS: 1 between driver and sidepod, 1 outside sidepod, then accumulator attachment load BCs are 20G lat/long/vert
- One layer of SIS: outside sidepod, then accumulator attachment load BCs are 40G lat/long, 20G vert

If you are not doing AFR for accumulator attachment, then I believe two layers of SIS are required. This is the shakiest part of my understanding, I am more confident about the AFR stuff.

[B757]

We were originally planning to use Headway LiFePO4 cylindrical cells, but after hearing mixed reports about their QC we're trying to get A123 AMP20 pouch cells. Unfortunately Formula Hybrid's EV3.8 rules on pouch cells are making us add significant amounts of filler material that roughly doubles the volume of the pack, so energy-density wise they're not great either.

We're trying to design a car that's also legal for Formula Hybrid (seeing as space for FSAE-Electric seems to be limited and there's a high chance we'll end up on the waitlist). As far as I'm aware FH doesn't accept AFR rules, though they don't have the same requirements for accumulator placement in the major structure so that might work out. Otherwise we're trying to see if having the sidepods count as a second layer of SIS works.