Yes but you then run into other ageing effects. One might hope >10 years things are still good, but how much longer can one expect?
There is the battery test centre in Australia:
batterytestcentre.com.au
Latest report, #10 in the series:
They cycle the batteries pretty hard, 2-3 cycles/day, so it's a form of accelerated stress testing, take that into account.
The outcomes on commercial battery reliability are woeful though.
Page 9 is a sea of red ink (battery failures.) Only a small fraction of the brands made it to test completion.
With so many single samples failing, we don't know if those which completed cycle testing just got lucky or that brand delivers consistently reliable product. Need results from a quantity of batteries to know MTBF. Or reports from all users, or a statistically valid sample.
Looks like lithium batteries for home use are a bleeding-edge product. Or many fly by night vendors.
Compare to EV, where a limited number of brands have relatively large number of cars on the road. Apparently their battery packs are mostly if not all good.
Regarding Samsung battery (which worked well up to almost 2800 cycles), "ITP believes that the SOC recalculation during the discharge cycle triggers standby mode and expects that these issues are due to cell voltage imbalances, which are typically exacerbated by aging."
People on this forum have said high balancing currents aren't needed, very slow active balancing is sufficient. Looks like higher rate balancing attempted to get more total Wh from batteries, but algorithm became unstable. Cells may have a cycle life and degradation in testing, but battery is a system that also has to work well.
"Redflow" flow battery - that's the sort I would hope could provide large capacity long term storage, because energy is stored in the electrolyte, in a tank. Similar to concept of a fuel cell, there is a component that allows chemical reaction and produces electricity, fed by storage of arbitrarily large capacity. But this one failed repeadly.
BYD: "In late August 2020, the battery’s internal DC breaker tripped during normal cycling and continued to trip after only a few minutes after reconnection to the SMA Sunny Boy inverter. BYD concluded that the battery stopped working due to the Sunny Boy Storage firmware being out of date and incompatible with the HVM battery. SMA and BYD were helpful and provided support to get the battery cycling again in November 2020. Since then, the battery has been cycling reliably."
I hate software.
My car has never experienced software incompatibility. Occasionally reports a failing sensor.
Interfaces between electronic boxes should use a communication protocol independent of software revision and backwards compatible, never breaking something that previously worked.
For grid tied I think that's a bit optimistic.
I would adjust it accounting for:
- portion of capacity that's sensibly useable
- reality that not every day will a battery go through a full cycle (low solar charge days, days not there etc), 60-70% is probably more realistic
- capacity will decline with age so and will creep up before getting 3500 cycles in
What you say is certainly supported by these test results.
Only the best of the batteries tested show they can reach the equivalent of 3500, 100% (original capacity) cycles (with capacity decline reducing actual cycle Wh)
The lithium batteries are showing round-trip efficiencies of 85% to 95%. Not as much higher than lead-acid as I expected, but this was at high C rates. Possibly lead-acid would perform even worse at those rates due to higher internal resistance. But June 2019 report says, "Round-trip efficiency between 85-95% had been observed for both the lead-acid and lithium-ion technologies, while linear extrapolation of capacity retention to date suggested that between 2,000-6,000 cycles could be delivered by properly functioning lithium-ion battery packs."
Prices in recent years for the batteries they tested have been $500 to $1000 per kWh, down from $2000 in 2015.
Compare the ~ $100/kWh for grade-B LiFePO4 individual cells bought by forum members.
If the DIY battery gave 3500 equivalent cycles, cost is $0.029/kWh, vs. commercial battery $0.145 to $0.29/kWh
That's about the price of wholesale utility generation vs. expensive market retail in the U.S.
"The capability of the manufacturer to diagnose faults remotely has proven valuable for some batteries. Ideally, this would not be required, but faults have proven common throughout the trial."
That makes you quite dependent on others, unless you can swap BMS and cells yourself.
Seems to me hot swapping of redundant battery assemblies is needed for reliability. Unless a brand is rock solid.
September 2019: "While some battery packs had experienced faults and/or failed prematurely, the Sony, Samsung, Tesla Powerwall 1, BYD, Pylontech, and GNB Lithium battery packs had generally demonstrated high reliability, with minimal issues encountered throughout the testing period."
April 2020, "The Sony and Samsung battery packs from Phase 1 have proven reliable, alongside the Pylontech and GNB Lithium battery packs from Phase 2."