2015 Battery rules change

[bobochacha]

Hi all ,

Hello everyone, I am Jun Jie from the National University of Singapore, FSAE team, working on the electrical component.

I am having a some issue with choosing a new lithium ion battery as the rules no longer allow anti-gravity battery.
Any one has any suggestion with brands or similar lightweight battery alternative.


IC4.4.4 Battery packs based on Lithium Chemistry:
a. must be commercially manufactured items
b. must have over voltage, under voltage, short circuit and over temperature cell protection
c. must be separated from the driver by a firewall



Any inputs is greatly appreciated (:

Jun Jie
NUS FSAE
Electrical Department

[MCoach]

What's wrong with the Anti-gravity batteries that prohibits them?

I think they have the battery protection built in.

[Swiftus]

What's wrong with the Anti-gravity batteries that prohibits them?

I think they have the battery protection built in.

Anti-Gravity batteries and all of the other LiFePO4 batteries on the market that I have found are not able to be used in Formula because they do not offer any over, under, or thermo protection. The Volt Phreaks batteries of a few years ago offered over and under voltage but no thermo protection. Additionally, the rules also state that the batteries have to be commercially available, which prevent a team from designing their own battery protection circuits (as we do in the electric car BMS boards).

Essentially, goodbye all lithium chemistry batteries unless you are willing to spend an arm and a leg.

[Kevin Hayward]

A couple of days ago the ECU team had an anti-gravity battery catch fire in a vehicle while it was idling. Myself and 5 students went to emergency from smoke inhalation. Thankfully everyone escaped with only burns to the throat and a few hours of feeling quite odd.

We had followed all directions on the battery, and had been using them for about 4 years.

Lightweight batteries are good, going to hospital is not. These rule changes are good.

Kev

[Swiftus]

Hey Kevin,

Sorry to hear about your incident. Hopefully all involved are alright.

Potential energy is a dangerous thing.

Were the anti-gravity batteries used in the car 4 years old? Or are you simply referring to 4 years of experience handling the anti-gravity batteries?

One of my issues with the anti-gravity battery is that it does not come with a balancing port. We have found with our work in LiFePO4 batteries that performing a balancing charge on the battery once a year is a very good indicator of the health of the battery. The Pulse batteries have a balancing connector and we have never experienced any problems with those batteries.

Do you know if the battery was in a hot or wet location? If it had been dropped ever in its life?

Even Lead-Acid batteries can be dangerous if grossly mistreated.

[MCoach]

Ah, Jay, I believe you're right. I would agree that one would have a hard time actually finding a LiFePO4 chemistry battery that met the requirements simply because they are typically considered safe enough to not need it, even for aeronautical applications. I was mistakenly thinking that several companies that offer them with balance boards had the management luxuries built in.

I could see those protections needed for some of the other...more volatile cells, such as the lithium polymer which have a tendency to burst in the flames from merely pronouncing it's name wrong, but again, even for highly stressed, high reliability requirement applications this is uncommon restrictions for the LiFEPO4 chemistry. It may or may not be a good idea to ban people from building their own packs for IC teams. On one hand, why not trust someone with a handful of cells when the EV cars are running many magnitudes over that and usually with cell C ratings that are in the upper echelon of the double digits (triple?). On the other, we've all seen how quickly something small, such as a battery deciding that its day has come, can start a fire and Kevin's story may contribute to that argument.

From my experience we tend to balance charge our batteries approximately every week or two, but we've had problems with people undervolting them in the past from cranking the engine too long and quickly killing them and so we try to care for them as much as possible. I thought Pulse built high performance polymer batteries packs or am I mistaken?

[Kevin Hayward]

Jay,

The battery was not 4 years old, we have been using the brand/type for about 4 years. At this stage we think it may have got a knock while traveling from the UK. We are fairly careful with the batteries. The battery was not hot, or wet. The team makes an effort to ensure electrical devices are mounted in sensible locations to avoid ignition, and heat effects.

The scary thing was that there was no warning that it was going to happen. One moment the car is running fine, the next the battery was going up. I am sure that some damaging event occurred at some point, we just can't identify what it was.

We are now in the process of going through the accident report and generating procedures to reduce the likelihood of it re-occurring as well as better procedures in the case of a fire.

Out of curiosity how long do teams run these batteries for? Also which lithium batteries (regardless of cost) meet the requirements?

Kev

[Swiftus]

I thought Pulse built high performance polymer batteries packs or am I mistaken?

Pulse uses A123 LiFePO4 cells. They have quality spot welding of the tabs to each cell and balancing circuits for each bank or cells.

Out of curiosity how long do teams run these batteries for? Also which lithium batteries (regardless of cost) meet the requirements?

Spontaneous is scary for sure!

I haven't actually found a battery which meets the current requirements (other than our eCar's battery). The closest I have come is our old Volt Phreaks battery which cost ~$800 (USD) new. A larger capacity Antigravity or Pulse battery (all use identical A123 cells) costs between $150 and $300.

[Dylan Edmiston]

Out of curiosity how long do teams run these batteries for? Also which lithium batteries (regardless of cost) meet the requirements?

My team has been running a Braille Li-ion battery for 2.5 years now (single battery).

[NickFavazzo]

We have recently had two go as well, mind you our battery was in such a location we could quickly remove it from the car and move it away from people and the car. I believe both times physical damage was the issue. Like any stored energy source, they require appropriate handling and care...