1.5V AA rechargeable batteries?

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Monza

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#275938 17-Sep-2020 14:59

I have a smart lock on the front door and very happy with it but about once a year it needs new batteries. It needs four 1.5V AAs but rechargeable ones from the supermarket etc are 1.2V. The non rechargeable ones default to 1.5V but would prefer rechargeable. Quick google says they do exist but certainly not very common.

What is the best way to get these in NZ? Again google found one NZ supplier but it says rechargeable alkaline which makes me think it is a typo. There does appear a few on Amazon. Don't mind paying extra for quality.

Scott3

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#2566892 17-Sep-2020 15:14

Note that while the 1.2v NiMH battery has a lower nominal voltage, its flatter decay curve means the voltage is acutally higher than a 1.5v alkaline for much of it's life.

I would say push some enaloop or enaloop pro batteries in and see how you go.

That said, my door lock has multiple warnings to only use Alkaline batteries. My assumption is that this is because it is relying on the gradual voltage dropoff to give a timely low battery warning. Perhaps consider planting a mechanical key outside if you are going to trial NiMH.

main variant of 1.5AA's I can think of are the USB rechargeable lithem ones. They have a converter to drop the voltage from 3.7v to 1.5v. I haven't tried these, but would assume that the standby draw of the converter would make them a poor choice for low draw, infrequent change / charge applications. Of course they would be great for an application where having the full 1.5V is really desirable.

muppet

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#2566894 17-Sep-2020 15:18

Don't buy 1.5V rechargables. There's no really good quality ones. Everything @scott3 said is correct. I would try normal AA rechargables (Eneloop only, don't bother with other brands they're just not as good) and see how it performs.

timmmay

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#2566906 17-Sep-2020 15:36

Just use Eneloop NiMH, they're 1.2V but work in the fast majority of devices. There are 1.5V rechargables but they tend to be expensive and niche. If Eneloop don't work get some carbon zinc or lithium batteries and put in a calendar reminder to change them every 9 months so they never go flat. I have similar reminders to charge emergency batteries, charge tool batteries, etc.

richms

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#2567078 17-Sep-2020 17:56

Once a year just buy alkalines and swap them out. Not worth the hassle for something with such a low turnover.

Richard rich.ms

neb

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#2567091 17-Sep-2020 18:32

I have two different non-contact voltage detectors, both reputable brands, and neither work from NiMHs, they require 1.5V batteries. It's really annoying since I use Eneloops for everything, but need to keep some alkalines around just to power the NCV. So there are some things that just don't work with NiMHs.

Monza

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#2567827 18-Sep-2020 18:52

Thanks for the suggestions. Have put some Eneloops in and so far no issues. Fairly sure last year I put in some Everyready NiMHs and it complained straight away.

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doug3

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#2567840 18-Sep-2020 20:23

To late, but if the 4 batteries are in series, 2 of these https://www.bunnings.co.nz/solar-magic-3-2v-600mah-14500-lithium-batteries-2pk_p4351891 with 2 dummy batteries will work.

neb

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#2567842 18-Sep-2020 20:35

doug3:
To late, but if the 4 batteries are in series, 2 of these https://www.bunnings.co.nz/solar-magic-3-2v-600mah-14500-lithium-batteries-2pk_p4351891 with 2 dummy batteries will work.

Ooh, very clever! I should try that in my NCVs since one + a dummy cell should do the job there.

Before I go out and buy a pack to make up this sort of frankenbattery, has anyone tried this?

Bung

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#2567849 18-Sep-2020 21:01

I think at least 1 of the early 2000s cameras (Fuji??) had the choice of using 1x3v CR123 or pairs of various AA types. You picked your choice in the settings menu to alter the low voltage detection.

neb

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#2567852 18-Sep-2020 21:06

Damn, and you can't get 10440 LiFePO4s in NZ which is what you'd need for AAAs, they're only available from dodgy Aliexpress sources. Which also sells (snort) 8800mAh 1.5V AAA rechargeables.

DonH

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#2567949 19-Sep-2020 10:32

One thing to watch with the solar light LiFePO4 cells - do not use a standard LiPo charger. They're a different chemistry with a lower maximum charge voltage.

People hear what they see. - Doris Day

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ezbee

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#2568023 19-Sep-2020 13:16

Nice thing on LiFePO4 is that its not prone to dramatic sudden destruction of LIPO.
So maybe chosen for safety ? Or just compatibility with LED voltage with minimum circuitry.
Trade off is less capacity than LIPO for same size.
Suppose vapers may be into these as well, for Safety given the reports of dramatic LIPO vape explosions.

Warning is the Charge voltage is lower for Life so don't put them on Lipo charger !

Though they do have requirement of minimum discharge voltage 2.5V
I wonder if low cost solar lights actually have cut off circuit,
or just wing it, and take cumulative damage as part lifetime limit ?
Have not found a teardown online for these Life ones.

I did find some more detail here.
http://www.smart-solar-lights.com/info/specification-of-the-lithium-iron-phosphate-l-20037899.html

Edit: That's probably not the right site to point to, ignore details there.

Better spec details for a similar 600mAh LiFePO4, but without specific datasheet from original MFG do be cautious.
https://www.sunlandpower.com/battery-for-lighting/solar-street-light-lithium-battery/ifr14500-aa-600mah-3-2v-lifepo4-battery-cell.html

Standard charging method
0.2C constant current,3.65V constant voltage charge to 3.65V,continue charging till current decline to ≤0.01C

Charge current 0.2C 120mA Standard charge, charge time about 7h(Ref)

1.0C 600mA Rapid Charge, charge time about: ::1.5h(Ref)

Standard discharging method 0.2C constant current discharge to 2.5V

lapimate

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#2568043 19-Sep-2020 14:47

Have you considered a separate battery-box? It could probably be mounted off the door (even in the attic) on the hinge side provided the cable has a coil at the hinge-line to take up the rotation of the door.

The battery-box could accommodate say, a 6V alkaline Lantern battery or perhaps 5 NiMH D-cells or even a 6V SLA.

The capacity of a non-rechargeable AA alkaline cell is about 2,700 mAH [see Battery capacities] whereas the capacity of a 6V alkaline square Lantern battery is 26,000mAH so if your current cells last, say 3 months you could expect a Lantern battery to last a couple of years.

neb

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#2568224 19-Sep-2020 18:21

DonH:
One thing to watch with the solar light LiFePO4 cells - do not use a standard LiPo charger. They're a different chemistry with a lower maximum charge voltage.

If they're non-18650s with matching cheap generic 18650-only chargers then the charger will probably be a universal one that knows about NiMH vs. LiFePO4 vs. standard LiIon, but yeah, good point to bear in mind.

neb

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#2568226 19-Sep-2020 18:24

ezbee:
Nice thing on LiFePO4 is that its not prone to dramatic sudden destruction of LIPO.

One word of caution though, they're safeer but still not inherently safe. Unfortunately you can't get protected cells in AAA sizes (10440), and probably not AA either (14500).