Question about battery chemical/fire safety

Kodack · Mar 4, 2021

I'm a long time RC enthusiast so I have a lot of experience with LiPo packs, and I don't trust them even a little. I store my small <5000mah 6 cell packs in ammo cans wrapped in ceramic wool for instance. Lipo doesn't just burn, it explodes outward and outgasses flames like a blast furnace.

I hope you can appreciate why I might have some questions before building cells many times larger, and keeping them in my house, where a battery event would almost certainly burn that room to cinders in seconds. The pack sizes we need for storage also don't make it easy to fling em out the door if they start to spit fire.

So is there something I'm missing in terms of safety?
Are the folks building 18650 packs relying on the individual cell canisters to be safe?
Are the LiFe packs that safe that you'd have several dozen kilograms of them in an area you sleep like an RV?
What are the chances of uncontrolled thermal runaway with the types of cells used in deep cycling?

Any information is appreciated.

After freezing my keister off for a week thanks to Texas blizzard 2021 I just want some emergency backup power without a generator, so I'm thinking a modes <300ah 24v LiFe system, which is still enough battery to scare me.

Steve_S · Mar 4, 2021

We do NOT recommend LIPO, NMC or other chemistries for use in ESS systems, especially those installed in any habitable structure.
LFP (LiFePO4) is by far the safest chemistry to use, even moreso than FLA.
Just about everyone here uses LFP. I'm presently running with 910AH and within 2 weeks once final testing and assembly is complete it will be 1,190AH / 30.464 kWh @ 24V.

Steve_S · Mar 4, 2021

As a separate add: Keep in mind that ESS Grade LFP discharges at 1C Rate and charges at 0.5C Rate. So a 280AH Cell/Battery will discharge up to 280A and take 140A Charge rate. A Typical 280AH cell weighs in at 5kg/11lbs.
4 cells = 12V, 8 cells = 24V & 16 cells = 48V

For a Fire Extinguisher, ONLY DRY CHEM units - Class D is prefered.

See links in my signature that will make your life much easier.
Hope it helps, Good Luck.

Will Prowse · Mar 4, 2021

I used to race drones and build long range FPV planes. I do not trust Li-poly. I know where every single lipoly cell in my house is located, and each one is in a fireproof enclosure. I never charge or discharge lipoly unattended.

With that said, most people build backup solar storage with LiFePO4 and sometimes LTO. These chemistries and their variants are extremely safe to charge while unattended.

There are some folks on youtube and other forums who build solar "powerwalls" with 18650 NMC and NCA variants. And sometimes lipoly packs. The cells they use are typically salvaged from electric vehicles. Or recycled laptop battery packs. These people can and do burn down their house's (check the powerwall group photos for proof) if the pack is not built properly.

I used to build with these cobalt based chemistries in the past without issue, but they are dangerous. I now avoid them like the plague. Owning any cobalt based cell that is capable of producing a self-propagating thermal runaway is a constant liability. That liability is increased when building the pack yourself, or storing/building large packs.

But technically, you can build with any chemistry. If you have new cells and a well-designed pack, it should work fine. But personally, I do not think it is worth the risk to use anything beside LiFePO4 and LTO for solar storage.

LiFePO4 is preferred for most because the voltage range and discharge curve is easy to work with standard 12/24/48V equipment, has a high cycle life, is extremely safe to use, and BMS options are plentiful.

Kodack · Mar 4, 2021

Will Prowse said:
I used to race drones and build long range FPV planes. I do not trust Li-poly ever. I know where every single lipoly cell in my house is located, and each one is in a fireproof enclosure. I never charge or discharge lipoly unattended.

With that said, most people build backup solar storage with LiFePO4 and sometimes LTO. These chemistries and their variants are extremely safe to charge while unattended.

There are some folks on youtube and other forums who build solar "powerwalls" with 18650 NMC and NCA variants. And sometimes lipoly packs. The cells they use are typically salvaged from electric vehicles. Or recycled laptop battery packs. These people can and do burn down their house's (check the powerwall group photos for proof) if the pack is not built properly.

I used to build with these cobalt based chemistries in the past without issue, but they are dangerous. I now avoid them like the plague. Owning any cobalt based cell that is capable of producing a self-propagating thermal runaway is a constant liability. That liability is increased when building the pack yourself, or storing/building large packs.

But technically, you can build with any chemistry. If you have new cells and a well-designed pack, it should work fine. But personally, I do not think it is worth the risk to use anything beside LiFePO4 and LTO for solar storage.

LiFePO4 is preferred for most because the voltage range and discharge curve is easy to work with standard 12/24/48V equipment, has a high cycle life, is extremely safe to use, and BMS options are plentiful.

Same. I have a chemical fire exteinguisher by my charging station along with a monitored smoke detector, and another in my garage where I store them with a 2nd monitored detector. Even having old cell phones and laptops laying around makes me nervous after seeing what a lipo fire looks like.

I'm glad to hear LiFe seems to be as safe as it appeared. I've heard a few people mention fumes though even with that one leak you had. I wonder if it's possible to create a sensor to tell if any liquid is weeping out of a pack internally. Like once you put a pack inside the external enclosure with a BMS, something that can pre-warn you it's leaking before you find it on your floor.

Question about battery chemical/fire safety

Kodack

New Member

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada

Will Prowse

Forum Owner

Kodack

New Member

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