Need help Figuring this FIRE out!

Speedy Gonzales

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Jun 9, 2022
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Hi Guys
Im new here, and this has been though to post. be lenient..

A few months ago I made a DIY Battery Golf car Replacement for a friend.
Here are the Specs:

3 X 48v 20ah
16S2P
A123 LFP 3.2v 20Ah Cells
Interconnect was done with screws
80v fuse at the main positive
The charger used was QuiQ, set to charger Trojan 1275.

I need help figuring out why this battery catched fire.
The only thing I know is that my friend called me 1 hr before these pictures telling be the cart would not run. like its not charging.
Asuming the charger was overcharging the batteries, these cells should not have catch fire.
I have my head scratching
View attachment 97499View attachment 97500View attachment 97502View attachment 97503
View attachment 97504




This was the middle battery that did not seemed to have fire damage:
View attachment 97518


This battery also went into thermal Runaway. Thats the only damage I could find on this one.
View attachment 97519
how did you connect the batteries?
Serial/parallel
 

Ampster

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Another thing with golf carts, they can consume a lot of current at startup
That is called the EV grin from any electric propelled vehicle. I am sure the golf carts are current limited when they put Lithiums in them. Without that I am sure the greens would be torn up very quickly. Lithiums can discharge at much higher rates than GEL or FLA.
 

Juan Gonzales

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Jun 6, 2022
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Hi Guys
Thanks all for your comments.

To answer some of the questions:
No... I was asking about the top balance procedure.
So, Top Balance was done connecting all cells in parallel, applying a charge with a Lifepo4 chinese Charger to 3.55 V and leaving the cells 24 hrs connected in parallel after the charger finished charging.

T-1275 go to 59.28V absorption and 64.8V equalization.
Thanks for this information. Have not been able to get the charger to work again. cant measure its Voltage.


That is called the EV grin from any electric propelled vehicle. I am sure the golf carts are current limited when they put Lithiums in them. Without that I am sure the greens would be torn up very quickly. Lithiums can discharge at much higher rates than GEL or FLA.
Please expand on this comment. I dont get your point. For Reference: Cells were 3.3v 20Ah pouch A123, capable of pulse discharge 600Amps for 10secs. & 200Amps for Continouse Current. so the Cart was not limited by the cells.


I also Found this on the Manufacturer`s Datasheet, Will attach it below
Maybe the fact that the cart was discharged to 0 a few times, streesed the cells enough that an overcharge to 64.8V created a fire.
1655410060833.png
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Eve Cells mentioned on their datasheet that they tested their cells to 5V overcharge and No Fire or Explosion. I cant find that on A123 datasheet.
1655411287499.png



1655409683063.png1655410371752.png
 

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Ampster

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Please expand on this comment. I dont get your point. For Reference: Cells were 3.3v 20Ah pouch A123, capable of pulse discharge 600Amps for 10secs. & 200Amps for Continouse Current. so the Cart was not limited by the cells.
I was responding to the comment by @brb58 who said that he had seen some muted acceleration with Lithium powered golf carts. I suspected that the motor controller was limited to prevent aggressive drivers who are thrilled by the EV grin. I did not want other readers to make the assumption that Lithium reduced the performance of former FLA powered golf carts.
 
Last edited:

brb58

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I was responding to the comment by @brb58 who said that he had seen some muted acceleration with Lithium powered golf carts. I suspected that the motor controller was limited to prevent aggressive drivers who are thrilled by the EV grin. I did not want other readers to make the assumption that Lithium reduced the performance of former FLA powered golf carts.
My opinion is that the motor controller limited the motor output so that the battery BMS wouldn't shutdown from an over current event. Of course in this case, there was no BMS LOL
 

RV10flyer

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The electrolyte can still combust. I like to think of LiFePO4 as safe as a stack of wood. Of course it will catch on fire if you get it hot enough. Many things will combust if you get them hot enough on this oxygen rich planet.
And when you burn magnesium metal, try to put it out with H2O, it produces hydrogen gas and the fire gets more exciting. Then you need to cover it in sand to put it out.
 

sunshine

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What chemistry are the pouch cells? Can anyone tell by the pouches?
I have no idea. There are no brands in the photos and alibaba seems to have LiFePO4 or Li polymer listed under that spec number.
There is even one with both chemistry listed.
 

Juan Gonzales

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What chemistry are the pouch cells? Can anyone tell by the pouches?
I have no idea. There are no brands in the photos and alibaba seems to have LiFePO4 or Li polymer listed under that spec number.
There is even one with both chemistry listed.
1655438731275.png
 

edcoopered

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I don't understand the logic in building a pack which you know is going to get destroyed by over discharge and overcharging in its first few cycles, and then relying on the chemical stability of LiFEPO4 that it doesn't turn into a blazing inferno. While the cell itself in a metal box (under test conditions) might not ignite, the problem is the cardboard and plastics around it in your example will ignite, the introduction of this flame will then cause the electrolyte to burn off as the battery vents. There's no getting around the energy density of these cells, if they fail they are going to get real hot.
 

chess-equality

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What can you guys say about temp monitoring? I know BMSes have high/low temp protection but what about other parts not controlled by the BMS? As I understand a golf cart is a compact vehicle which can be prone to heating issues (along with mechanical parts that also generate heat) especially when out in the sun.
 

hwse

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My JK BMS has two temperature probes that monitor the temp and control both high and low temperature cutoff. Where you put those probes will determine what is being monitored.
 

GSXR1000

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Hi Mike,
Thank you so much for your input.

I learned the lesson with "correct choice of a charging system"
Now I´m digging into the "A degree of care with design of the packs"

@RCinFLA your post was very helpful.

In my head, that still does not explain why it catched Fire.
Do you think the cardboard was the culprit? Carboard was used in the past for LFP Cylindrical cell covering.


@sunshine_eggo
Agreed about the BMS. Well past that. want to improve the design.
did you top balance all the cells in parallel before you assembled the battery.. not check for the same voltage.. at 3.1v they can be at 60% or 80% charged. so you have one cell group with a low state of charge. it will over voltage the other cells in the pack
 

GSXR1000

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I don't understand the logic in building a pack which you know is going to get destroyed by over discharge and overcharging in its first few cycles, and then relying on the chemical stability of LiFEPO4 that it doesn't turn into a blazing inferno. While the cell itself in a metal box (under test conditions) might not ignite, the problem is the cardboard and plastics around it in your example will ignite, the introduction of this flame will then cause the electrolyte to burn off as the battery vents. There's no getting around the energy density of these cells, if they fail they are going to get real hot.
golf carts are known to be driven till the battery is so drained that it slows down... which would murderer lithium.. the big reason to have a bms
 

Supervstech

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did you top balance all the cells in parallel before you assembled the battery.. not check for the same voltage.. at 3.1v they can be at 60% or 80% charged. so you have one cell group with a low state of charge. it will over voltage the other cells in the pack
The OP is not understanding the advice we are giving.

OP, we need a DETAILED STEP BY STEP OF WHAT YOU DID TO TOP BALANCE THE CELLS.

Once you have done this we can explain to you what you did wrong. We can explain how it should be done, and we can help you to prevent causing more injury in the future.
 
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