Purpose of this question:
In the interest of making my own BMS circuit designs safe and robust, i seek to understand causes of BMS failures in known systems. I'm not seeking consumer advice or general tips.
In 2015, as reported in the press, many hoverboards (mostly from Chinese manufacturers) caught fire. Some of the hoverboards exploded while charging, others while riding and one while it was simply sitting. Consumers from 24 states reported to the CPSC of 52 hoverboard fires resulting in more than $2 million in property damage over an 11-week period. Then they recalled 1/2 a million hoverboards. https://phys.org/news/2016-02-hoverboards.html
Were the infamous hoverboard fires caused by over-voltage charging, over-current charging, over-current discharging, short-circuits due to faulty cells, short-circuits due to faulty wiring or poor mechanical design, poorly-manufactured cells, or something else?
This article speculates problems with switches, cells, chargers... but all speculation.
K.M. Abraham, research professor at Northeastern's Center for Renewable Energy Technologies, stated that the cause is a combination of poor lithium ion battery manufacturing, combined with over-current discharge. He also mentions cell punctures. However, I've not been able to find a copy of his essay-- it's unclear whether his conclusions are based on investigative, forensic research, or just speculation.
This article speculates people might be using the wrong charger (which the USCP echoed that in their public statement). However, the article says the charger jack on the hoverboards is dissimilar to phone and computer charge-jacks, so that's unlikely-- there's no hard evidence that people are using the wrong charger. The also speculate people are overcharging the hoverboards, but again, no data.
While it's possible that each fire had a different cause, the fact that fires were happening repeatedly across the entire product category, including products from different manufacturers, in the space of just a few weeks, strongly suggests a common cause. The fact that UL and CPCS both conducted research to find "the cause" indicates that they too believe there's a common underlying cause.
CPSC devoted itself to finding the cause, but i've not been able to find their conclusions. https://incompliancemag.com/cpsc-investigates-safety-of-hoverboards/#respond
UL labs made hoverboard cells explode by pushing a nail into the center of the cell, and by applying indirect heat near the cell. But, we could make the cells from MANY products (which are not exploding during normal usage) explode in the same way.
UL reported: "some cells explode right away, others are built with backup measures designed to release gasses without bursting into flames."
That's approaching a possible solution, but then they'd have to show that gas build-up is the cause in actual hoverboard fires.
UL also conducted drop tests-- the hoverboard droped developed a serious crack, but it did not explode. That suggests puncture to the cells might not be the cause.
In May 2016, UL labs issued their first safety certification of a hoverboard, made by parent company of the Segway: https://incompliancemag.com/ul-certifies-the-first-hoverboard/
In July 2016, the CPSC announced the official cause: overheating lithium-ion batteries. But many things can cause a cell to overheat-- they don't say what caused the hoverboard fires. I've not been able to find their final report.
Robson Forensic states:
"outcome of their tests found that the lithium-ion battery packs can overheat, posing a risk of fire and explosion."
But that's not news-- every electronics hobbyist and professional who uses lithium ion batteries already knew that lithium-ion battery packs can overheat. But exactly what caused the hoverboard packs to overheat?
Please share data about relevant electronics design of actual hoverboards, not general safety tips. I'm not seeking consumer advice.