Rechargeable batteries worthwhile for smoke alarms?

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We have five wireless smoke alarms which are battery-powered and each take a 9V battery (the rectangular type). At present buying cheap supermarket non-branded alkaline non-rechargeable replacement batteries for these works out at about £6 a year on replacements because the batteries last about two years. So of course these devices have a very low power draw. I don't think we have any other commonly used devices that use 9V batteries of that physical size; we do have various devices that take AA and AAA batteries and we already have some rechargeable batteries and two chargers for those.
I've seen mention that rechargeable 9V batteries vary in their construction, with the result that it's recommended to get the charger and the battery from the same manufacturer.
Argos will sell me a battery charger that claims to recharge 9V batteries (as well as other types) for £25 ( https://www.argos.co.uk/product/9800830?clickPR=plp:5:5 )
and will also sell me rechargeable 9V batteries, from the same manufacturer, for £8 each ( https://www.argos.co.uk/product/9804070?clickPR=plp:4:5 )
So buying the batteries for all five smoke alarms, and the charger to charge them with, would cost a total of £65.
So that would mean a payback time of more than ten years, for which the charger and the batteries would need to last that long and the batteries would need to cope with being recharged probably at least six times each. And I would need to charge the batteries "for free" from my surplus solar generation (which is easy to do.)
Recharging the batteries every two years (or even half that) isn't significantly more of a chore than buying new non-rechargeable batteries every two years.
The batteries and the charger both only have a one year guarantee.
If this payback time was for a solar panel installation, it wouldn't be seen as particularly bad. And a solar panel installation can't easily be taken away when one leaves the house, whereas these items can. (Assuming they have a use at the new house.)
So, is it worth it?
And also, are there reasons that rechargeable batteries are particularly unsuited to very low power draw applications such as (wireless) smoke alarms?
I've seen mention that rechargeable 9V batteries vary in their construction, with the result that it's recommended to get the charger and the battery from the same manufacturer.
Argos will sell me a battery charger that claims to recharge 9V batteries (as well as other types) for £25 ( https://www.argos.co.uk/product/9800830?clickPR=plp:5:5 )
and will also sell me rechargeable 9V batteries, from the same manufacturer, for £8 each ( https://www.argos.co.uk/product/9804070?clickPR=plp:4:5 )
So buying the batteries for all five smoke alarms, and the charger to charge them with, would cost a total of £65.
So that would mean a payback time of more than ten years, for which the charger and the batteries would need to last that long and the batteries would need to cope with being recharged probably at least six times each. And I would need to charge the batteries "for free" from my surplus solar generation (which is easy to do.)
Recharging the batteries every two years (or even half that) isn't significantly more of a chore than buying new non-rechargeable batteries every two years.
The batteries and the charger both only have a one year guarantee.
If this payback time was for a solar panel installation, it wouldn't be seen as particularly bad. And a solar panel installation can't easily be taken away when one leaves the house, whereas these items can. (Assuming they have a use at the new house.)
So, is it worth it?
And also, are there reasons that rechargeable batteries are particularly unsuited to very low power draw applications such as (wireless) smoke alarms?
7.25 kWp PV system (4.1kW WSW & 3.15kW ENE), Solis inverter, myenergi eddi & harvi for energy diversion to immersion heater. myenergi hub for Virtual Power Plant demand-side response trial.
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I will mention that one of my old AA/AAA battery chargers still works despite being twenty years old, although it's not been in regular use that whole time, and certainly none of the batteries that came with it have survived that much regular use.
2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 2.5kw inverter. 28MWh generated, long-term average 2.6 Os.
I use these in my smoke alarms https://docs.rs-online.com/fabf/0900766b81549eff.pdf and they last around 10-11 years (our preset one is eleven years old and the smoke alarm is still function (it detected the burnt toast yesterday)
Other makes are avaialble, Varta, GP, Energiser - https://www.batterystation.co.uk/battery-types/lithium-batteries/9v-lithium-batteries.html
Note they are non rechargeable lithium, not rechargeable lithium-ion
Not sure I'd go down the rechargeable route if I hadn't already, might be better to have a stronger and longer lasting 'proper' battery in them.
Sorry to be so 50:50 about it.
For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
Ionisation ones (no longer sold/recommended) due to depletion of the radioactive material. Others simply down to sensor aging and altered efficacy / response times to smoke (fire).
Even mains operated interconnected alarms, where the battery is just a backup for power cuts.
Smoke alarms are available with 10 year life lithium cells included. In both standalone and mains versions. Consider buying them when you next need a new smoke alarm. The lifetime cost is probably lower, and certainly more convenient.
2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 2.5kw inverter. 28MWh generated, long-term average 2.6 Os.