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You are planning to charge the thing overnight and use it exclusively during the day, nearly exhausting it each time? The battery is going to wear out well bef

You are planning to charge the thing overnight and use it exclusively during the day, nearly exhausting it each time? The battery is going to wear out well before 10 years. If you oversize your battery so you are only pulling out half the charge in the battery[1], you can probably get 1500 cycles out of it[2]. That's still less than 5 years. (This is a common pattern if you are trying to price-compare an electric car to a gas car. For the electric car, the electricity cost is a rounding error compared to the capital cost of the battery, so you can just about assume electricity is free, and worry instead about how long the battery will last.) You will get a much bigger bang-for-the-buck by demand-shifting: if the biggest load is cooling your building in the heat of the day, run the A/C overnight to superchill a heat sink that can be accessed during the day. No battery installation needed. [1] Toyota did this with the Prius. They purposefully did not use the full range of the battery because they wanted the battery to last 7+ years. [2] http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries http://batteryuniversity.com/learn/article/how_to_prolong_li...

kbenson 11y ago
It comes standard with a 10 year warranty, with an optional 10 year extension. If they don't have different numbers than you, I don't see why they would even attempt that.
- danielweber 11y ago
  Warrantied to what, though. That you can still get 20% capacity levels in year 10, or that it will still turn on? This might be considered "normal wear and tear." 3000 deep cycles is really pushing what the industry knows to be state of the art. Maybe they are just taking the economic chance that most people won't be deeply cycling these batteries, and planning to do replacements for those who actually put it through its paces.
  - kbenson 11y ago
    > Warrantied to what, though. That's a good question, and it makes a big difference. > That you can still get 20% capacity levels in year 10, or that it will still turn on? This might be considered "normal wear and tear." Given that you can optionally warranty it for an additional 10 years, I doubt it's nearly that bad. If people are confused as to how they how they hope achieve 10 years reliability, and they are willing to warranty 20 years, they must have something up their sleeves. > 3000 deep cycles is really pushing what the industry knows to be state of the art I suspect that the powerwall's true capacity is higher than it's rating, and it uses that reserve so it's not doing deep cycles, similar to another commenter's assertion to how the Prius gets it's 7+ year rating, > Maybe they are just taking the economic chance that most people won't be deeply cycling these batteries, and planning to do replacements for those who actually put it through its paces. I think a combination of most users not fully cycling every day, extra reserve capacity to keep it from deep cycling, and some subset of people not using failing warranty conditions may all contribute.

kbenson 11y ago

It comes standard with a 10 year warranty, with an optional 10 year extension. If they don't have different numbers than you, I don't see why they would even attempt that.

danielweber 11y ago
Warrantied to what, though. That you can still get 20% capacity levels in year 10, or that it will still turn on? This might be considered "normal wear and tear." 3000 deep cycles is really pushing what the industry knows to be state of the art. Maybe they are just taking the economic chance that most people won't be deeply cycling these batteries, and planning to do replacements for those who actually put it through its paces.
- kbenson 11y ago
  > Warrantied to what, though. That's a good question, and it makes a big difference. > That you can still get 20% capacity levels in year 10, or that it will still turn on? This might be considered "normal wear and tear." Given that you can optionally warranty it for an additional 10 years, I doubt it's nearly that bad. If people are confused as to how they how they hope achieve 10 years reliability, and they are willing to warranty 20 years, they must have something up their sleeves. > 3000 deep cycles is really pushing what the industry knows to be state of the art I suspect that the powerwall's true capacity is higher than it's rating, and it uses that reserve so it's not doing deep cycles, similar to another commenter's assertion to how the Prius gets it's 7+ year rating, > Maybe they are just taking the economic chance that most people won't be deeply cycling these batteries, and planning to do replacements for those who actually put it through its paces. I think a combination of most users not fully cycling every day, extra reserve capacity to keep it from deep cycling, and some subset of people not using failing warranty conditions may all contribute.