4 ms·

When I looked into battery storage a couple of years ago to go along with rooftop solar, it was still far from making sense economically. The number of years it

When I looked into battery storage a couple of years ago to go along with rooftop solar, it was still far from making sense economically. The number of years it would take me to recoup my investment on a battery was something like 15 to 20 years - longer than the typical warranty on a battery. (Note that I don't live in sunny California). With electricity prices increasing, and many power companies paying less for electricity fed back into the grid, it will certainly make storage batteries more appealing. But I suspect they are still too expensive to make financial sense in many regions. And once a significant percentage of households have installed battery storage, I expect power companies will start raising their flat service fees to ensure they can keep earning their sweet, sweet profits.

lightedman 4y ago
I would suggest not looking at new battery tech, and instead look at far more mature (but bulkier) storage tech. Just get a bank of AGM batteries for your wall. 12V, 100+Ah. That's 1,200w per battery. To match a 13.5kWh Powerwall, you need 12 (you'll slightly-exceed the Powerwall.) Renogy 100Ah 12V batteries are ~$200, so $2400 total for the required 12. Tesla Powerwall is almost $13,000. You can get 4-5,000 0-100-0 cycles with the AGMs, The Powerwall gets you about 3,000. 12 batteries doesn't take up a huge amount of space, either. Inverters/charger/instant-switchover systems run around $3-5K depending upon solar array power (up to 20kWh.) B-grade panels still last 30 years until 70% output, produce all the same power as their a-grade brethren, yet only cost about $80 for a 310w panel in bulk (and that was5-ish years ago when I was manufacturing them) so ~$320 in solar to generate 1.2kWh at full tilt. $3,840 to be able to refill your entire battery bank in one hour in full sunlight in optimal conditions. For not even the price of the Powerwall alone, you can have power self-sufficiency. Dump that saved money into basically doubling your storage, and never worry about energy again, in reality. ~1% degradation per year on the solar panel means even in 50 years you're still pushing ~7kWh full-tilt, that's around what most current residential systems push today. You're actually ahead of the game using older tech.
- FrojoS 4y ago
  Your calculation on AGM batteries is false, AFAIK. AGMs (basically lead acid batteries) have a much lower lifetime (about 300 cycles, not 5'000 [1]) versus LifePo4 (Lithium iron phosphate, ~2'000 cycles [1]), to the point where it doesn't make economical sense to buy an AGM today [1]. As an example, you could get six 12.8V, 200 Ah LifePo4 incl. BMS from a US supplier for 3'5000 USD [2]. That will give you 15kWh (not w) of storage, so, more than the 'Powerwall' you cite and much more than your AGM batteries. Your calculation has another mistake, I think. With AGM batterie, you can only use 50% of the labeled energy [2], so your calculation is off by another factor of two. With LifePo4 you can use about 80% of the labeled capacity, if you want to get a long lifetime out of your LifePo4 battery. From another Source [1]: [LifePo4] Up to 6 time the cycle life AGM Deep cycle – 300 cycles @ 100% DoD LiFePO4 – 2'000 cycles @ 100% DoD Benefits: Lower total cost of ownership (cost per kWh much lower over life of battery for LiFePO4) Reduction in replacement costs – replace the AGM up to 6 times before the LiFePO4 needs replacing [1] https://www.sealedperformance.com.au/faq/what-are-some-differences-between-lithium-and-agm-batteries/ https://www.sealedperformance.com.au/faq/what-are-some-diffe... [2] https://ipowerqueen.com/collections/12-8v-series/products/12-8v-200ah-lifepo4-battery-built-in-100a-bms https://ipowerqueen.com/collections/12-8v-series/products/12... [3] https://www.crownbattery.com/news/agm-vs-flooded-batteries-what-you-need-to-know#:~:text=AGM%20batteries%20perform%20most%20reliably,than%2050%25%20of%20battery%20capacity https://www.crownbattery.com/news/agm-vs-flooded-batteries-w.... (edited for formatting and typos)
  - lightedman 4y ago
    I have Trojan AGMs that are well over 20 years old in my Golf Cart. They've had well over 2,000 charges and are still pushing nearly 90% capacity. No swelling, no leakage, nothing. My grandfather's old flood-chargeable lead-acid golf cart batteries were double that age, or more, and had an easy 10K deep cycles on them when he passed. That cart went two rounds of 18 holes, plus fishing at the water traps afterwards, daily. He would change the fluid in them monthly. Typical unsealed lead acid batteries can be maintained to last a long time. We used those to power an old warehouse with a solar array for a natural living commune in Memphis for over a decade. I can't tell you exactly how long they lasted as I had moved away from there while after that tenth year. Now once the plates have totally sulfated over, yes you aren't getting power unless you strip the sulfates away to reveal the plates again, but until then, acid refreshes work just fine, and you're looking at about 15 years before needing to replace the batteries due to sulfur coating if you only bother doing acid refreshes. You can get far longer if you know how to remove the sulfur off the lead plates. The days of sub-1000 cycle deep-cycle lead-acid batteries have long gone. All it takes is knowing how to maintain them. Nobody seems to do that any longer. Most of these were made with maintenance cycles in mind. (Not AGMs, obviously, they're totally-sealed.)

lightedman 4y ago

I would suggest not looking at new battery tech, and instead look at far more mature (but bulkier) storage tech. Just get a bank of AGM batteries for your wall. 12V, 100+Ah. That's 1,200w per battery. To match a 13.5kWh Powerwall, you need 12 (you'll slightly-exceed the Powerwall.) Renogy 100Ah 12V batteries are ~$200, so $2400 total for the required 12. Tesla Powerwall is almost $13,000. You can get 4-5,000 0-100-0 cycles with the AGMs, The Powerwall gets you about 3,000. 12 batteries doesn't take up a huge amount of space, either. Inverters/charger/instant-switchover systems run around $3-5K depending upon solar array power (up to 20kWh.) B-grade panels still last 30 years until 70% output, produce all the same power as their a-grade brethren, yet only cost about $80 for a 310w panel in bulk (and that was5-ish years ago when I was manufacturing them) so ~$320 in solar to generate 1.2kWh at full tilt. $3,840 to be able to refill your entire battery bank in one hour in full sunlight in optimal conditions. For not even the price of the Powerwall alone, you can have power self-sufficiency. Dump that saved money into basically doubling your storage, and never worry about energy again, in reality. ~1% degradation per year on the solar panel means even in 50 years you're still pushing ~7kWh full-tilt, that's around what most current residential systems push today. You're actually ahead of the game using older tech.

FrojoS 4y ago
Your calculation on AGM batteries is false, AFAIK. AGMs (basically lead acid batteries) have a much lower lifetime (about 300 cycles, not 5'000 [1]) versus LifePo4 (Lithium iron phosphate, ~2'000 cycles [1]), to the point where it doesn't make economical sense to buy an AGM today [1]. As an example, you could get six 12.8V, 200 Ah LifePo4 incl. BMS from a US supplier for 3'5000 USD [2]. That will give you 15kWh (not w) of storage, so, more than the 'Powerwall' you cite and much more than your AGM batteries. Your calculation has another mistake, I think. With AGM batterie, you can only use 50% of the labeled energy [2], so your calculation is off by another factor of two. With LifePo4 you can use about 80% of the labeled capacity, if you want to get a long lifetime out of your LifePo4 battery. From another Source [1]: [LifePo4] Up to 6 time the cycle life AGM Deep cycle – 300 cycles @ 100% DoD LiFePO4 – 2'000 cycles @ 100% DoD Benefits: Lower total cost of ownership (cost per kWh much lower over life of battery for LiFePO4) Reduction in replacement costs – replace the AGM up to 6 times before the LiFePO4 needs replacing [1] https://www.sealedperformance.com.au/faq/what-are-some-differences-between-lithium-and-agm-batteries/ https://www.sealedperformance.com.au/faq/what-are-some-diffe... [2] https://ipowerqueen.com/collections/12-8v-series/products/12-8v-200ah-lifepo4-battery-built-in-100a-bms https://ipowerqueen.com/collections/12-8v-series/products/12... [3] https://www.crownbattery.com/news/agm-vs-flooded-batteries-what-you-need-to-know#:~:text=AGM%20batteries%20perform%20most%20reliably,than%2050%25%20of%20battery%20capacity https://www.crownbattery.com/news/agm-vs-flooded-batteries-w.... (edited for formatting and typos)
- lightedman 4y ago
  I have Trojan AGMs that are well over 20 years old in my Golf Cart. They've had well over 2,000 charges and are still pushing nearly 90% capacity. No swelling, no leakage, nothing. My grandfather's old flood-chargeable lead-acid golf cart batteries were double that age, or more, and had an easy 10K deep cycles on them when he passed. That cart went two rounds of 18 holes, plus fishing at the water traps afterwards, daily. He would change the fluid in them monthly. Typical unsealed lead acid batteries can be maintained to last a long time. We used those to power an old warehouse with a solar array for a natural living commune in Memphis for over a decade. I can't tell you exactly how long they lasted as I had moved away from there while after that tenth year. Now once the plates have totally sulfated over, yes you aren't getting power unless you strip the sulfates away to reveal the plates again, but until then, acid refreshes work just fine, and you're looking at about 15 years before needing to replace the batteries due to sulfur coating if you only bother doing acid refreshes. You can get far longer if you know how to remove the sulfur off the lead plates. The days of sub-1000 cycle deep-cycle lead-acid batteries have long gone. All it takes is knowing how to maintain them. Nobody seems to do that any longer. Most of these were made with maintenance cycles in mind. (Not AGMs, obviously, they're totally-sealed.)