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Electric bicycle reliability.

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e100:
If you plan to keep the bike in your house then LiFePo4 batteries are the least likely to catch fire.

However most e-bikes today ship with batteries that use a different lithium chemistry because of the higher energy density and lower weight. Unfortunately these tend to go into inferno mode when a fault develops.



Siwastaja:

--- Quote from: e100 on September 18, 2020, 04:44:26 pm ---If you plan to keep the bike in your house then LiFePo4 batteries are the least likely to catch fire.

--- End quote ---

Not true. Proper high-quality NCA cells are safer than sub-standard LFP cells, and the problem with LFP is, you practically only get substandard cells.

e100:

--- Quote from: Siwastaja on September 18, 2020, 06:00:04 pm ---
--- Quote from: e100 on September 18, 2020, 04:44:26 pm ---If you plan to keep the bike in your house then LiFePo4 batteries are the least likely to catch fire.

--- End quote ---

Not true. Proper high-quality NCA cells are safer than sub-standard LFP cells, and the problem with LFP is, you practically only get substandard cells.

--- End quote ---

from https://batteryuniversity.com/learn/article/types_of_lithium_ion
"High energy and power densities, as well as good life span, make NCA a candidate for EV powertrains. High cost and marginal safety are negatives."

james_s:
My friend's family has several e-bikes, they've had them for about 3 years now I think and so far they're all going strong. Battery life will depend heavily on how you much you ride and how you treat it. If you keep the battery away from high temperatures and don't store it fully charged (unless it's LiFePO4) it should last well. 5 years is probably a reasonable minimum if not abused.

Siwastaja:

--- Quote from: e100 on September 19, 2020, 02:14:56 am ---from https://batteryuniversity.com/learn/article/types_of_lithium_ion
"High energy and power densities, as well as good life span, make NCA a candidate for EV powertrains. High cost and marginal safety are negatives."

--- End quote ---

Cathode material theory is different from actual products on the actual market. Actual cells have much more than just the cathode material, including flammable electrolyte, for example.

Claim about cost is similarly wrong, At about $300/kWh, LFP is almost twice as expensive as NCA as it stands; again, looking at actual production cells, not some theoretical raw material cost. This is due to price fixing in Chinese LFP market, the small size of said market, and the economies of scale of modern high-energy density cell types such as NCA.

LFP cathode also has potential thermal runaway, just the onset temperature is higher and released energy is smaller. Energy and power density of LFP cells is more than enough to bring the cells to runaway (somewhere around 300 degC IIRC) whenever the cells fail internally or are abused externally. The result is slighly less dramatic than with NCA but can nevertheless easily lead in total loss of property. A few youtube videos showing a single LFP cell shorted in open air and "only" releasing smoke and not fire does not mean they don't cause fire when packaged as larger packs in real-world installations. A modern NCA cell in similar abuse conditions typically does not release even the smoke, because it has several layers of protection (missing from the typical LFP cell).

LFP was dead-end; NCA has seen all the development by the big players, including safety.

Numerous fires have occured in DIY LFP conversions.

Really, the key is to only use good brand cells. If you have/want to buy crap (which I don't have objection against), I wouldn't lull into the false sense of security of LFP, just accept crap is crap and may catch fire regardless of the claimed cathode chemistry. I will correct each time someone posts this "LFP is safer" crap on forums. I have seen enough evidence of the exact opposite.

The root problem is mixing battery science with consumer product selection. There is a long way from not understanding theory, to understanding it, and then understanding the market. If you try to make engineering / buying choices based on science popularization sites like Battery University, you are guaranteed to go wrong.

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