TP Link Kasa AA rechargeable batteries for TRVs?

waqasahmed

So

Most TRV vendors say you shouldn't use rechargeable batteries and you can get around it using this 

US $3.20 | Universal 3/4.5/6V AA LR6 Battery 3V AAA Battery Eliminator USB Power Supply Cable with Switch

https://a.aliexpress.com/_EHluzxQ

Which is a touch unsightly, though I was also wondering, surely one could use 1.5V lithium AA batteries? 

QrizB

waqasahmed said:

Most TRV vendors say you shouldn't use rechargeable batteries

Usually this is because most rechargeable batteries have relatively high self discharge, so you'd be changing them every month or two.

You might be able to use Eneloop-type low self discharge rechargeable batteries. Might be worth trying those?

waqasahmed said:

...

 surely one could use 1.5V lithium AA batteries? 

What's the self-discharge rate on those? Most rechargeable lithium cells have a voltage of 3-4V, so "rechargeable lithium AAs" include a buck regultor to drop the voltage 1.5V. There will be a parasitic load, but I don't know how large a one.

It's occurred to me that you might be able to power a smart TRV with a Peltier cell, but I've never tried!

Rodders53

I have used some AA rechargeable Lithium cells to power a Blink camera.  Type with a USB socket in the side.  They seem to be working fine after more than a year.  My Blink doorbell has been complaining of low (original) battery form the past couple of months.  I'll replace with a pair of rechargeable.   

I can't comment on any AAAs.  Nor whether any would be suited to the TRV use.

NiMh cells are 1.2V and that will be the killer for things that need 1.5V to drive stuff.

I'd be inclined to try them if the cost wasn't prohibitive compared to using a decent brand of dry cells (annual replacement)?  I go for Duracell Procells usually.

Grizzlebeard

An even bigger problem with NiMh rechargeables is the nominal 1.2V instead of 1.5V for  Alkaline.

The TVR (or anything else) thinks the battery is almost depleated even when brand new.

Depending on the cut-off voltage threshold of the electronics, usually between 1.15-1.2V, it might be detected as a completely dead Alkaline after just an hour or two of use.

(Same problem with my TV/Freeview/etc remote controls.)

Gerry1

You can get Li-ion 1.5V rechargeable AA and AAA cells. They charge very quickly.

However, they radiate interference all the time which prevents their use in AM radios, presumably because they have an always-on DC-DC converter on the motherboard to step down the voltage.  Unlikely to be a problem with TRVs, but something to bear in mind with other devices.

waqasahmed

Rodders53 said:

I have used some AA rechargeable Lithium cells to power a Blink camera.  Type with a USB socket in the side.  They seem to be working fine after more than a year.  My Blink doorbell has been complaining of low (original) battery form the past couple of months.  I'll replace with a pair of rechargeable.   

I can't comment on any AAAs.  Nor whether any would be suited to the TRV use.

NiMh cells are 1.2V and that will be the killer for things that need 1.5V to drive stuff.

I'd be inclined to try them if the cost wasn't prohibitive compared to using a decent brand of dry cells (annual replacement)?  I go for Duracell Procells usually.

They're not that expensive to buy tbh. But yes my issue was thinking the voltage simply wouldn't register as a genuine amount of power 

I did wonder if the chemistry itself mattered if say any BMS

waqasahmed

QrizB said:

waqasahmed said:

Most TRV vendors say you shouldn't use rechargeable batteries

Usually this is because most rechargeable batteries have relatively high self discharge, so you'd be changing them every month or two.

You might be able to use Eneloop-type low self discharge rechargeable batteries. Might be worth trying those?

waqasahmed said:

...

 surely one could use 1.5V lithium AA batteries? 

What's the self-discharge rate on those? Most rechargeable lithium cells have a voltage of 3-4V, so "rechargeable lithium AAs" include a buck regultor to drop the voltage 1.5V. There will be a parasitic load, but I don't know how large a one.

It's occurred to me that you might be able to power a smart TRV with a Peltier cell, but I've never tried!

Not sure what the discharge rate is but I've used them in a radio controlled clock and they last a few months or so. Less battery life than disposable but also far better for the planet. Having TRVs also = better for the planet