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DI water fire suppression?
#1
So I am stockpiling hundreds of Sanyo 18650 cells just because I have a constant supply of cells that were removed from service on a time basis, rather than a failure basis. I plan to use these cells in a land speed race car or motorcycle project. In planning the battery, I would like some sort of fire suppression system and, since the electrolyte supplies its own O2, I am wondering why I couldn't design a bladder full of DI water to rest atop the battery. If one cell were to "blow torch," it would quickly burn a hole in the bladder and self-extinguish with DI water (or at least cool the pack to help avoid a chain reaction burn). Since DI water is in the Mega ohm range, I don't foresee the whole pack shorting out by being drenched with DI water. Am I way off-base in this assumption?

PS: I realize this is posted in the Solar & Wind section; I do plan on charging this system with solar panels while on the salt flats. The concept is to prove that you can go 200mph using the sun's energy instead of burning fossil fuels. 
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#2
Interesting project. I'd love to see that race.

However, using the Sanyo cells probably wouldn't be the best. You'd want to use the high amp output cells like those in powertools. Unless you plan on running the cells at full power a couple runs and then toss them. The high amp draw required to run motors, especially at the speeds you're asking, will kill the cells, if they can even delivery that kind of current.
Assuming voltages for the motors is over 48V. How many watts are the motors rated at?

The DI water would only help suppress the heat, nothing more, as stated. But why carry the extra weight of water? You could use sand, which is a bit lighter. Or just don't pack the cells so close together to allow for air cooling.
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#3
Also, internal resistance (IR) of cells increase with age (or cycle count?). Higher IR => less current the cells can provide and/or more heat they generate when doing so. Neither of which you want when building a speed record machine....
although... Are you talking about short distance sprint record, or a long distance marathon speed record?

For the former, sell the Sanyo cells and get new cells with better suited chemistries, such as LiFePO4, Lithium-titanate or even supercapacitors.
For the latter, your Sanyo's could work, depending on which model. But you'll want to build a battery with cells matched for capacity AND IR, otherwise you'll be carrying dead weight you can't use.
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#4
(06-10-2019, 08:38 PM)Ohm\s Law Wrote: So I am stockpiling hundreds of Sanyo 18650 cells just because I have a constant supply of cells that were removed from service on a time basis, rather than a failure basis. I plan to use these cells in a land speed race car or motorcycle project. In planning the battery, I would like some sort of fire suppression system and, since the electrolyte supplies its own O2, I am wondering why I couldn't design a bladder full of DI water to rest atop the battery. If one cell were to "blow torch," it would quickly burn a hole in the bladder and self-extinguish with DI water (or at least cool the pack to help avoid a chain reaction burn). Since DI water is in the Mega ohm range, I don't foresee the whole pack shorting out by being drenched with DI water. Am I way off-base in this assumption?

PS: I realize this is posted in the Solar & Wind section; I do plan on charging this system with solar panels while on the salt flats. The concept is to prove that you can go 200mph using the sun's energy instead of burning fossil fuels. 

Water = weight, the enemy of racers!
Any water on the cells = corrosion = pack lost.
On salt flats, you'd get salt dust everywhere, any water would mix with salt = quite conductive water.... + even more corrosion!
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#5
Most likely you'll also need some serious cooling. Hot lithium battery => dead cells and/or flaming pile of hot metal. At the least some serious capacity degradation.
Adding to Redpacket, condensation might be of concern in the early morning hours, which could turn really ugly if there's salt dust inside the pack.

Perhaps a better approach is to put the whole battery into a sealed tub and fill it with mineral oil. Add some piping, a pump, a radiator, thermostat and a fan. Depending on actual oil type, flammability in case of a leak might be a concern. Don't think the submerged battery can ignite the mineral oil without a replenishing supply of oxygen, but don't quote me on that.
Just throwing ideas here, not saying it's a good one.

...considered cheating by using a Tesla pack? I think it has excellent cells and the industry-best cooling system.
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#6
(06-11-2019, 12:53 PM)ajw22 Wrote: Don't think the submerged battery can ignite the mineral oil without a replenishing supply of oxygen, but don't quote me on that.

Lithium Ion batteries carry their own Oxygen. So, uh, yeah. No problem getting Oxygen. However, the oil idea would help lower the heat buildup which could keep a cell from actually igniting in the first place. Buuuuut, oil is as heavy as water, if not heavier, depending on the oil.
If each cell was in it's own heat resistant (read as >500F resistant) polymer tube, this could isolate the cell from the others in case of an eruption. As long as the ends of the tube were not facing another pack that is. Could use a divider plate that makes the flames go up and out the top of the vehicle in case of fire.

As ajw22 says, just throwing ideas out there.
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#7
Yep.

To extinguish lithium-ion fires, you need to get rid of the heat.

The higher the heat generation, the faster it'll thermal runaway.

Water should just be used as a last resort, and in the form of a water spray to maximize surface area.

To prevent thermal runaway, there are multiple things that can be done:
1. Use low resistance cells. Less heat=more efficiency=less chance of a disaster in bad conditions.
2. Use nickel plated copper buses for connections, as to lower the resistance as much as possible.
3. Use thin diameter copper/aluminium wire for the cell connections as a high performance fuse that can rapidly blow when necessary.
4. Make a pouch that can fit between the cells filled with high melting point paraffin wax to stomach heat spikes.
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#8
Thanks everyone for the responses and ideas. I do need to clarify a few points:

-This is land speed racing on the Bonneville Salt flats which is generally 5 miles to reach maximum speed and at least 2 miles to slow down. (parachute)
-I will have a push vehicle to push me to about 60mph before "lighting it up," so that would give me a bit more time before the battery heating begins.
-"Weight is the enemy of racers," except in land speed racing, where many racers add weight (often bolting a 1000lb 1" thick slab of steel to the underside of the car) to make the car stick to the course by not allowing air to pass between the tires and the course. Aerodynamic downforce increases aerodynamic drag, so it's a no no in LSR. LSR is a battle between aerodynamic drag and horsepower. 
-I realize the 5.9A 2400mAh Sanyo cells are not ideal for this but they are $free.99 and the concept of this project is reduce, reuse, recycle. I do have a steady supply of 10A Sony cells, but not nearly as many as the 5.9A Sanyos.  I realize that I will need more of these 5.9A cells to equal the output of high current cells. But, this negates the need for ballast weight. Also, I plan on building this battery pack in a modular design so I can easily add some capacity to lower performing stages as well as adding higher current cells to the module as they become available.

The series wound brushed motor(s) will likely be direct drive to the wheels and they will be sourced from old forklifts. 
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#9
Apparently the bulk of the cells I have are Sanyo UR18650E with a max discharge of 6.1A.

https://www.simpower.co.nz/wp-content/up...18650E.pdf
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