Mitsubishi Outlander PHEV Forum
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Battery fire hazard
http://www.myoutlanderphev.com/forum/viewtopic.php?f=10&t=4420
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Author:  yardbird88 [ Tue May 14, 2019 9:36 pm ]
Post subject:  Battery fire hazard

Tesla has a few reports of battery caught fire while charging. I start to worry that our outlander overnight charging may pose fire hazard. Any reported incidence for outlander PHEV at all. I intend to install a smoke alarm in the garage soon.

Author:  greendwarf [ Wed May 15, 2019 2:07 am ]
Post subject:  Re: Battery fire hazard

Never seen any mention of it in the last 4 years but the Tesla battery is much bigger so heat build up during charging will be greater, especially when using their Superchargers.

Author:  elm70 [ Wed May 15, 2019 5:00 am ]
Post subject:  Re: Battery fire hazard

A Volvo PHEV got on fire in UK time ago ... while was charged at home

Battery can always explore and go on fire .. if overcharged, even without a super charger

"Overcharge" issue could happen with battery ageing

Since our battery get charged only up to 4.1v , and the max voltage should be around 4.3v before get troubles ... we should be on the safe side

Still .. nobody knows how this PHEV might behave when it will have a 10y old battery inside.

Author:  yardbird88 [ Wed May 15, 2019 5:32 pm ]
Post subject:  Re: Battery fire hazard

I got a GFI outlet to stop any upsurge of current while charging at night. Crossing my fingers that we won't be woke up by smoke or fire. :roll:

Author:  yardbird88 [ Thu May 16, 2019 1:26 pm ]
Post subject:  Re: Battery fire hazard

A client of mine who is both an electrical engineer & chemist told me that The Tesla batteries are just a bunch of little lithium (like your AA batteries) sticks, nothing high tech because they can mass produce those and bundle them together. It is probably similar in our PHEV. He said once it caught fire, you can't stop it with water because it makes the fire worse. However he told me not to worry as the chance of overheat and fire is pretty small just like your iphone's.

Author:  ps44 [ Thu May 16, 2019 2:07 pm ]
Post subject:  Re: Battery fire hazard

Just remember not to drive your PHEV into the sea :lol:
https://bc.ctvnews.ca/caught-on-camera-electric-suv-plunges-into-water-at-port-moody-boat-launch-1.4425001?fbclid=IwAR28kauCAgAg4KhOH-6O40t72yMvLukpgy6XFHepvBP0fXCUpn3_ZxYiJjI


And that Volvo PHEV fire was an arson attack https://www.thetimes.co.uk/article/fire-destroys-volvo-hybrid-xc90-as-it-is-charged-outside-family-home-zsgcr29nx

Author:  elm70 [ Thu May 16, 2019 11:57 pm ]
Post subject:  Re: Battery fire hazard

yardbird88 wrote:
A client of mine who is both an electrical engineer & chemist told me that The Tesla batteries are just a bunch of little lithium (like your AA batteries) sticks, nothing high tech because they can mass produce those and bundle them together. It is probably similar in our PHEV. He said once it caught fire, you can't stop it with water because it makes the fire worse. However he told me not to worry as the chance of overheat and fire is pretty small just like your iphone's.


Tesla use 18650 / 21700 lithium cells ... possibly 3.6v nominal voltage .. each cell is 3.4Ah / 5Ah .. they need around 7000/3000 (3000 on model 3) of these for make the full battery pack

Our PHEV use big prismatic cells. nominal voltage is 3.75v .. and we have only 80 of these big cell in our PHEV .. and only 600 of these would be needed for make a 100kwh pack like on a Tesla S100

So ... a very different technology used between Mitsubishi and Tesla

Our battery pack should be water proof, people crossing on deep water will cause to fully submerge our pack ... I would not gamble on the water proof safety of our pack, but so far nobody reported any issue

About eventual fire ... even if it is just 12kwh pack ... it is just good to remember that the Rimac Concept One destroyed by Grand Tour, got on fire short after the crash, and was burning for over 1 week.

Back to the question if it is dangerous to charge the car in a garage :
- There is not a single accident
- Unless battery degradation is very high , the risk is practically zero.
- Once the battery will be very old (10y or more), with a SOH below 40% ... then yes ... it is possible that :
Quote:
Lithium metal plating inside the battery creates extremely hazardous conditions that may lead to fires or even exploding batteries


My understanding is battery degradation is mainly due to battery plating. This can cause a short and eventual fire/explosion especially when the battery is fully charged

I believe the BMU might prevent the charge of our battery if battery degradation is too high .. so before the car can go on fire, I believe it will refuse to get any charge or it might reduce the max charging voltage from 4.1v down to 4.0v ...or even less

Another difference between Tesla and Mitsubishi .. it is that the tesla has 70/50 battery in parallel .. so if one goes bad, it has many cells in parallel which might cause a burst on current flow from the good cells into the bad one .. but for prevent this, they have a simple "fuse" on each cell, that will melt in case of high current flow

Since out PHEV has only 80 cells in series, and none in parallel .. we don't have this issue .. but a big cell can still fail inside and since it is big, it has lot of energy which might cause fire or explosion

Author:  jaapv [ Fri May 17, 2019 2:35 am ]
Post subject:  Re: Battery fire hazard

As the official wading depth of the car is 40 cm, I wuld ssume that the waterproofing is adequate.

Author:  yardbird88 [ Fri May 17, 2019 9:08 am ]
Post subject:  Re: Battery fire hazard

elm70 wrote:
yardbird88 wrote:
A client of mine who is both an electrical engineer & chemist told me that The Tesla batteries are just a bunch of little lithium (like your AA batteries) sticks, nothing high tech because they can mass produce those and bundle them together. It is probably similar in our PHEV. He said once it caught fire, you can't stop it with water because it makes the fire worse. However he told me not to worry as the chance of overheat and fire is pretty small just like your iphone's.


Tesla use 18650 / 21700 lithium cells ... possibly 3.6v nominal voltage .. each cell is 3.4Ah / 5Ah .. they need around 7000/3000 (3000 on model 3) of these for make the full battery pack

Our PHEV use big prismatic cells. nominal voltage is 3.75v .. and we have only 80 of these big cell in our PHEV .. and only 600 of these would be needed for make a 100kwh pack like on a Tesla S100

So ... a very different technology used between Mitsubishi and Tesla

Our battery pack should be water proof, people crossing on deep water will cause to fully submerge our pack ... I would not gamble on the water proof safety of our pack, but so far nobody reported any issue

About eventual fire ... even if it is just 12kwh pack ... it is just good to remember that the Rimac Concept One destroyed by Grand Tour, got on fire short after the crash, and was burning for over 1 week.

Back to the question if it is dangerous to charge the car in a garage :
- There is not a single accident
- Unless battery degradation is very high , the risk is practically zero.
- Once the battery will be very old (10y or more), with a SOH below 40% ... then yes ... it is possible that :
Quote:
Lithium metal plating inside the battery creates extremely hazardous conditions that may lead to fires or even exploding batteries


My understanding is battery degradation is mainly due to battery plating. This can cause a short and eventual fire/explosion especially when the battery is fully charged

I believe the BMU might prevent the charge of our battery if battery degradation is too high .. so before the car can go on fire, I believe it will refuse to get any charge or it might reduce the max charging voltage from 4.1v down to 4.0v ...or even less

Another difference between Tesla and Mitsubishi .. it is that the tesla has 70/50 battery in parallel .. so if one goes bad, it has many cells in parallel which might cause a burst on current flow from the good cells into the bad one .. but for prevent this, they have a simple "fuse" on each cell, that will melt in case of high current flow

Since out PHEV has only 80 cells in series, and none in parallel .. we don't have this issue .. but a big cell can still fail inside and since it is big, it has lot of energy which might cause fire or explosion

That's good to know. thanks.

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