2015 Battery rules change

[Swiftus]

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

I don't think any Braille batteries offer thermo protection. Over and Under voltage, yes.

[coleasterling]

I may be speaking falsely here, but I want to say that EarthX has a battery with thermal protection, at least in prototype form. They do have a bms with under and over voltage for sure.

[Swiftus]

... but I want to say that EarthX has a battery with thermal protection, at least in prototype form...

If they ever sell, I and every other FSAE team on the planet will buy it because they will have cornered the market.

[Dylan Edmiston]

I contacted both Ballistic Performance Components and Braille Battery regarding this topic. Both said their batteries do not meet the rules. The response I got from Braille was more in depth and stated that the batteries they make have short circuit/over voltage protection, but lack undervoltage protection to eliminate an extra failure point that can be a safety hazard (can cause powered systems to shut off on the track) and reduce cost and size. The description goes even more in depth about the safety of their batteries (which you will find in Indy, DTM, Formula 1, etc...).

I'm sure many other lithium batteries have the same certifications and low risk of failure as Braille.

[apalrd]

I contacted both Ballistic Performance Components and Braille Battery regarding this topic. Both said their batteries do not meet the rules. The response I got from Braille was more in depth and stated that the batteries they make have short circuit/over voltage protection, but lack undervoltage protection to eliminate an extra failure point that can be a safety hazard (can cause powered systems to shut off on the track) and reduce cost and size. The description goes even more in depth about the safety of their batteries (which you will find in Indy, DTM, Formula 1, etc...).

I'm sure many other lithium batteries have the same certifications and low risk of failure as Braille.

Forward it to the RC?

The previous rules exempted lithium iron phosphate from the rule (IC4.4.4) which regulates lithium batteries.

This seems to be due to a change in the EV rules. New EV rule for 2015:

EV3.1.2 There are no concessions for using LiFePO4 chemistry cells.

Previous EV rules (from 2014):

EV3.1.2 If the cells that are used in the accumulator are based on LiFePO4, then some regulations do not
apply, see EV3.4.8 and EV3.6.6.

Specifics from 2014 EV:
-Accumulator segments must be separated by electrically insulating barrier. For non-LiFePO4, barrier must be fire resistant
-Temperature of at least 30% of cells must be monitored by AMS, for lithium based cells except LiFePO4
-GLV Battery packs based on Lithium Chemistry other than LiFePO4 must have over voltage, under voltage, short circuit and over temperature cell protection and be separated from the driver with a firewall.

They even said they were going to make this change (here's from the 2014 rules):

T15.12 EVs: For EVs the committee is considering the following regulations changes:
....
- treat LiFePO4 cells the same as Li-Ion cells
....

and then they applied the proposed EV change (which many IC people probably didn't even read) to the IC rules as well.

[Dylan Edmiston]

Forward it to the RC?

I'm going to make a rules question sometime tonight with the info and direct them to Braille since the contact there offered to talk with the RC about this. If I find anything major out I'll post here.

[apalrd]

That's awesome that Braille offered to talk to the RC.

I hope the RC reconsiders, because I kinda like the Shorai LiFePO4 batteries we have run for 2 years now (no issues, we do put it behind the firewall).

[Dylan Edmiston]

While LiFePO4 batteries have some safer properties than other Lithium chemistries when it comes to thermal runaway there are still certain conditions that should be avoided. In particular these are overcharge and over temperature which would be protected by the required BMS. There are multiple companies making Lithium 12V batteries which include the safety systems required in the FSAE rules.

This is the response I got. As far as I know, they didn't attempt to contact Braille and talk about this.

[MCoach]

While LiFePO4 batteries have some safer properties than other Lithium chemistries when it comes to thermal runaway there are still certain conditions that should be avoided. In particular these are overcharge and over temperature which would be protected by the required BMS. There are multiple companies making Lithium 12V batteries which include the safety systems required in the FSAE rules.

In my experiences, lead acid cells should also not be over charged or over temped as well. Lead acid batteries when overcharged or over temped tend to release flammable hydrogen gas and spew sulfuric acid if it comes unsealed. Sometimes when charging, they'll outright explode... I guess now that all of the common lithium cells are protected by the BMS only teams with a shorted lead acid battery will burst into flames.

[Krister2]

"There are multiple companies making Lithium 12V batteries which include the safety systems required in the FSAE rules".
We have not been able to find any batteries with "temperature cell protection". Can somebody share their findings?

Krister
Lund Unversity Formula Student Team
Sweden