[FTC]: Tetrix Battery Pack Internal Short Circuit

[charrisTTI]

The students were taking their parts and robot chassis out of the storage container yesterday, when one of them called out to me, "Hey our battery pack is smoking!".

We disconnected the battery pack from the robot and took it outside until the "fireworks" were over. Both the black and red wires were cool, except that the black wire had come unsoldered from the tab on the battery. The fuse was not blown. Only the first cell at the negative end of the stack got hot. It appears that the metal tab attached to the end of last battery, to which the black wire is soldered, cut through the heat shrink insulation and the plastic covering of the adjacent battery. The case (-) of the adjacent battery is connected to the terminal (+) of the last battery, so when the tab connected to the case, there was a direct short across the last cell.

(see attached picture)

[EricVanWyk]

Ooooh! Pretty thermal event!

Please talk to FTC HQ about this as soon as possible.

[charrisTTI]

Done.

Lego Education has been informed as well and is exchanging battery and requested return of the defective unit.

[davidfv]

OK.. it is not an isolated occurrence. I had just taken two batteries out of the box hooked them up to two new chargers. I was in the same room the whole time during the charge. Did not smell anything. When I picked them up to disconnect, I noticed one was on it's side the other up-right. I picked up the one on its side, it was warm and it started smoking. I do not know if being on it's side was a contributing factor, but could be used as a precaution. Almost the exact same picture as charrisTTI.

The one charging up-right was not warm and was indicated fully charged.

[DonRotolo]

From an engineering point of view, SOMEone will be very interested in getting this second battery pack for inspection. Please make sure that it doesn't just get tossed, but into the right hands.

[Rick TYler]

This happened a lot last year. We had two packs fry.

[davidfv]

Originally Posted by Don Rotolo

From an engineering point of view, SOMEone will be very interested in getting this second battery pack for inspection. Please make sure that it doesn't just get tossed, but into the right hands.

Absolutely. As soon as I hear from Lego Education on where send it.

[JohnFogarty]

This same thing happened at the World Nationals last year during a match the team's battery practically exploded.

[PhilBot]

On basic precaution that we take is to always charge at 0.9A, and not at 1.2A.

When a low pack is charged at 1.2A it gets VERY hot. Probably hot enough to soften any plastic insulation/heat shrink. We had two packs show signs of leakage as well. Both went bacl to LE.

No recomendations were EVER given as to the charger setting, so I bet most teams charge as fast as possible.

Originally Posted by John_1102

This same thing happened at the World Nationals last year during a match the team's battery practically exploded.

[Tony Allen]

Recent reports indicate that rare instances of TETRIX Battery Pack burn-out have occurred in which battery packs overheated and produced smoke. In even fewer cases, the battery pack has omitted sparks.

It has been determined the largest contributing factor to battery pack burn-out is the puncturing or damage of the battery pack casing, typically caused by improper robot construction. Customers are encouraged to reference the TETRIX Getting Started guide for important safety guidelines and building best practices.

LEGO Education and Pitsco Education will continue to investigate this issue that has currently occurred in less than .2% of all battery packs shipped to date.

If you experience battery burn-out, unplug the battery immediately and contact LEGO Education Technical Support at 800-362-4308. Defective battery packs will be replaced free of charge and should be sent to LEGO Education for tracking purposes.

All LEGO® Education and Pitsco Education products are manufactured, packaged, and sold with the utmost regard for the safety of our users. We regret any inconvenience caused by this issue and welcome all comments and questions.

Care and Safety Tips:
The following are some basic battery pack care and safety tips that will help preserve the life of your battery pack.

-Never leave battery on charger unattended for extended periods of time.
-Pay close attention to not mount battery pack on robot where it may come into contact with sharp
edges or protruding screws.
-To increase battery life and performance, we recommend charging your TETRIX battery pack on the
slower charger setting of 0.9 amp.

Thanks
Tony Allen