The UPS coddling the M2 printer began complaining about a bad battery, so I ran (nearly) all the UPS batteries through the tester:
The two blue flubs in the lower left come from the failed battery, with the dotted trace after charging to 13.7 V and letting the current drop to 20 mA.
The red and green traces come from two other UPS batteries installed in 2016, with the dotted traces after charging similarly. The orange-ish trace is from the battery in a Cyberpower UPS bought in 2016, so it looks like all batteries of that vintage fade equally.
Except for another pair of batteries in another UPS that had discharged stone cold dead; it may have been shut down and unplugged during a power outage and they never quite recovered.
After five years, it’s time to refresh the fleet …
The Smell of Molten Projects in the Morning 
Tesla Powerwall?
How many days under snow do you get a year? You might make a case for some solar panels if it’s low enough
Or an SMR? ;-)
“Nuclear submarine reactors could be used to make mini power station at Trawsfynydd”
The main axis of the house is kinda north-south, so the broad surfaces see the sun less than half the time. Worse, Mary refers to her garden in the back yard as “the shade garden”, which should give you an idea of how little sun gets through the trees.
Our next house, should we ever get one, might be better suited for solar power …
Re UPS batteries…
In a previous life one of my responsibilities included about 50 APC UPSes ranging from 600 watts to 3kw scattered across a dozen customer locations. All used 12v sealed batteries… some used one or two of the 12v 7AH ones in parallel, the higher power ones used two of the 12AH in series, and the 3kw one used 4 of the 16AH in series, and three add-on battery boxes in parallel each with 4 more.
Back when I could get USA-made batteries I could get at least 4 years out of a set of new gell-cells, sometimes 5 years. When all of the “manufacturers” switched to japanese, tiwanese, malaysian or korean built crap the life dropped to 3 years. After one cycle of battery replacements I recommended to all of the customers that they go to 2.5 years. I put a reminder for each UPS into a calendar on my computer. Last I knew the UPSes are still on a 2.5 year battery cycle… the “pulls” are still good, they are donated to the local ham radio club.
I’ve been told by a friend that works in the biomedical group at a major hospital that APC runs the batteries “harder” (his word) than Best, or Cyberpower, Tripp-Lite, Eaton, or any of the other small UPS manufacturers. He takes care of the electronics for a local group that owns several convalescent hospitals.
I’ve not done any reverse engineering of small UPSes, I don’t know.
Interestingly the local bank branch used to have a dozen APC UPSes… Not any more. Three years ago they moved to a new building (the landlord doubled the rent on the old place, and it’s still vacant today). They built a new building a block away and put a 5kw Libert UPS in the server room of the new place and had the underfloor wiring of the desks run to the server room. No more small UPSes.
I recently replaced all the batteries in one of my UPS units – a 6kVA Falcon containing 20 x 12V 7Ah batteries. I installed them at the end of 2009 but replaced 10 at various times in the intervening period whenever the UPS tossed out a battery error. My simplistic test to identify duds was to measure the voltage on each battery – anything under 12V was replaced. 5 replacements in the past year suggested the rest were approaching EOL and it was time for a new batch
BTW the most reliable UPS’s I’ve had were made by Best – still have one I installed in 1994, don’t think the batteries have been changed in it more that 3 or 4 times
I just scrapped out a Belkin with IC date codes of 02: definitely exceeded its Best Used By limit, even though the electrolytic caps still looked good.
Gave up the hulking multi-kilowatt ferroresonant UPS some years ago after replacing all four of its car-size SLA batteries too many times. It produced enough quasi-sine-wave always-online power for all the hardware around here, but it was so noisy it had to live in a soundproofed box in the basement.
Batteries: BAH!
I suspect the pertinent question is do you need ups at all?
Back in the day when I ran mostly desktops and Raid5 array it seemed like a necessity. Nowdays I run just one non laptop machine and snap raid (file level raid). Since my last ups gave out around 10years ago I havent looked back.
I would however appreciate some power wall like solution to keep the lights on in admittadly rare power out events
The power company has definitely improved their overall reliability, but we still have occasional blinks during storms and some protracted outages due to collisions. Getting a few minutes for an orderly shutdown definitely helps, because all our PCs are cheap off-lease Optiplexes.
I agree with Mike – current generation gel cells in desktop UPS applications simply don’t last as long as (US-made) batteries two decades ago did. My 1500W Belkin UPS internal gel cells gave up the ghost years ago and were replaced by a pair of external 17Ah (gel cell) motorcycle batteries – and they still provide great capacity after more than 7 years of use. (And we get our share of power outages here in the land of the People’s Electric Cooperative.)