Way back in 1978, I bought a “Forever” battery for my vehicle (from JCPenneys). My father laughed, saying there was no such battery.
He was right but then he was also wrong. The battery did go dead eventually, but JCPenney had made a promise to replace it - for free! - if it ever went dead or failed.
I had that vehicle up until the 1990s and every couple years a new battery for free.
OK, so it isn’t solar but it lasted “forever”.
I bought the same type of battery from a Kragens store. Dead two years later, and they no longer sold them -plus they stated that there never should have been one sold for the ‘older’ car that I had. The manager was polite enough about it, and gave Me their longest lasting, most expensive battery as a replacement for free. Too much trouble to argue, so just took the replacement one.