nz_lifer
Member
- Joined
- Aug 26, 2020
- Messages
- 87
As practice of my assembly technique for the power wall I am making a medium? sized 4.2kWh power bank.
3s208p. 624 cells total.
Built into a rolling tollbox as it will weigh 40+kg by the end of it.
One of my concerns was what happens in case of fire?
Can it be contained or at least directed up without setting stuff nearby alight.
1. Build the power bank from scratch with fire resistant materials. eg steel
2. Modify something off the shelf to suit.
Option 1. Cost and time.
I do not have the tools / work space to complete the build.
I do have access to a workshop nearby but not as convenient as working on something when you have 30mins spare here and there.
It can be done.
https://electrek.co/2016/12/19/tesla-fire-powerpack-test-safety/
Option 2 it is.
To help with fire proofing,tile underlay (concrete board) will be used to sandwich the cells.
Make it as 3 separate layers. 2 separators per layer. A total of 9 fire cells.
The sides of the container will be coated with fire proofing silicone.
Strategic internal partitions to direct fumes/flames up and away from other electronics.
Fans to draw in air.
Through a foam filter as it will be used in dusty environments.
The cells are generously spaced to help with heat dissipation.
Max peak power will be 0.5A per cell. Limited by the BMS.
With individual cell fusing and the BMS monitoring temperature/voltage, there should be a very low chance of fire.
Separate environmental monitoring board with own battery to monitor temperature in case BMS fails.
I still wanted to test the fire silicone for my own piece of mind.
A small 2x3 pack was constructed of rejected cells.
Some plastic was covered with 4mm of silicone.
Thermal camera at the ready.
Let the science being
As always be extra careful around these cells. The potential for damage/injury is HIGH when abused.
Test 1. No fire
My test power supply only went up to 5A.
It warmed up the cell but no fire.
The cells warmed, 70c, up then went open circuit. I tested 3x.
Test 2. No fire
Heat up the cells directly with a blow torch. Propane > 1100c.
After a minute I though it was not a good idea to be that close to one if it actually vented.
Still it got at least to 240c (Max of thermal camera) and still no venting.
Those cell holders sure let off a bit of black smoke.
Test 3. Fire.
I gave up trying to get one into thermal runaway and attacked the plastic directly.
The fire proof silicon did it's job well
3s208p. 624 cells total.
Built into a rolling tollbox as it will weigh 40+kg by the end of it.
One of my concerns was what happens in case of fire?
Can it be contained or at least directed up without setting stuff nearby alight.
1. Build the power bank from scratch with fire resistant materials. eg steel
2. Modify something off the shelf to suit.
Option 1. Cost and time.
I do not have the tools / work space to complete the build.
I do have access to a workshop nearby but not as convenient as working on something when you have 30mins spare here and there.
It can be done.
https://electrek.co/2016/12/19/tesla-fire-powerpack-test-safety/
Option 2 it is.
To help with fire proofing,tile underlay (concrete board) will be used to sandwich the cells.
Make it as 3 separate layers. 2 separators per layer. A total of 9 fire cells.
The sides of the container will be coated with fire proofing silicone.
Strategic internal partitions to direct fumes/flames up and away from other electronics.
Fans to draw in air.
Through a foam filter as it will be used in dusty environments.
The cells are generously spaced to help with heat dissipation.
Max peak power will be 0.5A per cell. Limited by the BMS.
With individual cell fusing and the BMS monitoring temperature/voltage, there should be a very low chance of fire.
Separate environmental monitoring board with own battery to monitor temperature in case BMS fails.
I still wanted to test the fire silicone for my own piece of mind.
A small 2x3 pack was constructed of rejected cells.
Some plastic was covered with 4mm of silicone.
Thermal camera at the ready.
Let the science being
As always be extra careful around these cells. The potential for damage/injury is HIGH when abused.
Test 1. No fire
My test power supply only went up to 5A.
It warmed up the cell but no fire.
The cells warmed, 70c, up then went open circuit. I tested 3x.
Test 2. No fire
Heat up the cells directly with a blow torch. Propane > 1100c.
After a minute I though it was not a good idea to be that close to one if it actually vented.
Still it got at least to 240c (Max of thermal camera) and still no venting.
Test 3. Fire.
I gave up trying to get one into thermal runaway and attacked the plastic directly.
The fire proof silicon did it's job well