The history of batteries is fascinating, and I'm reading Charged: A History of Batteries and Lessons for a Clean Energy Future by James Morton Turner (University of Washington Press. Kindle Edition). One of the things I was surprised to learn, though I suppose I shouldn't have been, was that AA batteries take roughly 160(!) times more energy to manufacture than they produce in their lifetime. And that recycling them often uses more energy than it saves (transportation). Since the removal of mercury from the battery cathode, they're environmentally harmless in a landfill. The whole recycling push was because of mercury, which is no longer part of the battery chemistry.
What I'm trying to learn now is the relative cost of NiMH rechargeable batteries. They're not addressed in this book, as he focuses on the history of lead-acid, AA disposables and lithium-ion, with the materials extraction environmental costs.
I'm also reading DIY Lithium Batteries: How to Build Your Own Battery Packs by Micah Toll, not to "build my own," but to learn about them from a practical sense. The more I learn, the happier I am that we installed the mini-split ac in the garage.
We run our Powerwalls in the Tesla recommended mode of maintaining a 20% reserve capacity. This means we often go to the grid for power sooner than we'd otherwise have to. But it also acts as a whole-house UPS, with about 5kWh of battery reserve in the event of a power outage. It also helps preserve the useful lifetime of the batteries, where by "useful," I'm referring to maintaining as much capacity as possible for as long as possible, while still making practical use of them. The hybrid hot water heater and induction range also help in that regard by being lower current demand appliances, and now the dryer is lower demand as well.
At this point, I think the highest demand service in our house now is recharging the RAV4 Prime. I've tried to schedule trips such that the car is back in the garage early in the day when it can be recharged from solar and/or battery, though now I think it's perhaps at least as smart to allow it to charge from the grid. (We would still net-out positive as solar production that wouldn't go to recharging the battery after charging the car would most likely go to the grid, and that high current flow is not an issue for the batteries.)
They're warrantied for 80% capacity at 10 years, but that doesn't mean they're useless when the capacity dips below 80%. Rather than replace them, I'd probably look to add another battery.
It's forecast to be an active hurricane season, and I'm skeptical that northeast Florida enjoys some permanent geographical advantage in terms of hurricane risk. In the event of a near-miss that left our place habitable but without power, air-conditioning becomes the "vital load," not only for comfort but for keeping the humidity down in the house to prevent the growth of mold.
The "Storm Watch" feature of the Powerwall software will actually charge the batteries from the grid prior to a major storm event, and switch to grid power for the duration. If there's a large or long outage, we'd enter the problem with a fully charged battery, and hopefully the clouds pass with the storm and the array keeps the batteries charged, though it may take some additional care and attention on our part.
So I'm pretty confident in terms of our preparedness. We'd have to monitor cloud cover and our power consumption in the event of an extended outage, but I'm pretty sure I can keep the important things running, chiefly AC and refrigerator, though, really, if we lost the food in the fridge, it wouldn't be catastrophic. I think the AC is only truly "vital" load, especially as we get older.
Anyway, started out with AA battery facts, ended up with aging in place in a hurricane-prone state. What's up with that?
Originally posted at Nice Marmot 05:21 Tuesday, 9 April 2024