5kWh of battery cells at the moment run around $500. The rest of the cost of production is in the power electronics (probably around another $500).
It's why you can buy 4kwh worth of battery backups from Amazon for about $2k right now. Yet the same thing sold as a home battery backup costs $5k.
Lack of competition and likely low amount of sells is what's causing the margins to be so high.
Propane generators here have the same problem.
That still doesn't explain the price gap. You can literally just get a V2H EV and use it instead of a home battery (or, you could if the ecosystem was more mature).
They want ~9k for a freaking 13.5kwh pack.
I can buy a UL certified, 16kwh, outdoor rated pack for 3.5k (ex - EG4 allweather)
I can buy just the LFP batteries themselves for the new powerwall 3 LFP version (no BMS, no shell, no certification) for $1116... https://18650battery.com/products/byd-302ah-3-2v-lifepo4-pri...
Powerwall is a scammy product. WAY too expensive for the storage it provides.
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So the summary is: Cybertruck is using a different battery chemistry, Powerwall is a scam.
(I mean - to be clear, the Cybertruck is also a scam, but it's a different kind of scam not directly related to the battery capacity, since it's hauling around a 123kWh NCMA battery pack)