Rechargeable 1.5V lithium batteries

You can also wonder what a device can do with these batteries that depends on the internal resistance of a battery like a cheap camera flash...

And yes, these batteries are definitivly a bad solution for something like this:

On Sat, 06 Dec 2025 16:27:19 -0500, legg snipped-for-privacy@nospam.magma.ca> wrote as underneath :

A thing I found is that the permanantly attached buck or boost regulator in these batteries, (PP9 EBL with USB boost reg. in my case) can drain the LiPo well below ideal V either in storage or instruments that are only used occasionally, so worth keeping an eye on that type of very life shortening behaviour! I would suspect the 1.5v might follow the samee pattern except with a buck reg.. C+

In equipment designed for regular primary cells, the best you could hope for was a low battery indicator, which usually gets ignored until performance is visibly affected.

With rechargeable bodies employing who-knows-what inside the can, things are different. You're counting on the internal BMS qualities of the adopted internal interface circuitry.

For micro-dollar devices from multiple vendors, the results are going to vary.

One of the most common occurences in application specific captive battery protection interfaces is a discharge to below values required for the protection system to maintain function. These may refuse to start or to be recharged - into the trash bucket. Often this is simply the result of a badly selected voltage monitoring chip, or a poor understanding of the 'who's on first' logic created by the interface to the charging and protection hardware with which the voltage monitor is attached.

I've seen product that attempted to improve product life (where previously the end user was allowed to discharge the lithium cell to rubbish) by introduction of a voltage monitoring switch. A considerable number (not all) of the resulting units protected the battery at a level where the pre-existing recharging circuitry lost it's function - an unspecified or untested feature of the custom silicon involved.

This probably corrected in the next iteration, if there ever was one, but I doubt the experience is shared between multiple designers. Very likely it will be different designer, each time.

RL

Note the use of batteries in some of the test settups, to avoid excess noise sources and reduce ground loops.

If they'd counted on them to absorbe transients, they might also have been dissapointed.

Testing a low noise buck regulator is one thing; testing for battery terminal noise and its effects on downstream circuitry is another - and something few will anticipate to be required.

RL

I think it comes out in the wash, considering the energy density improvement of the mockingbird's chemistry.

- if you can actually get at the real battery terminals.

- with these, 'all' you seem to need is a USB source.

Who would have thought that USB would turn out to be the most widely used consumer power interface . . .

RL

Given the wide range of configurations, you'd have to examine each individually, to answer your concerns.

Some AAA rechargeables actually include a micro-usb charging port - but I see vendors phasing these out in favor of two terminals and internal (active) diode wizardry.

RL

Devices that depend upon the supply to absorb energy will have a surprise. A 6V stack of rechargeable 1.5V cells 'may' clamp at about 17V . . . . .

Switched-mode-audio, or any kind of bridge or clamped topology. I suppose caps will fill in , in most cases. Anything used to running off a buck regulator won't see a difference.

RL

I have some AA and AAA ones and have measured them unloaded (well, apart from the 10M of the multimeter) and they were OK, I mean no noticeable up/down on the readout, have not looked at them with the scope. Just got them on aliexpress, no brand I can remember. I have two AAA in an IR thermometer which must have very low consumption while "off", nothing of interest has happened in well over a year. I managed to damage one of the two AA in my torch, the latter will sometimes not go on with the button and needs a strongish hit with a palm. I opened it, the wire from the PCB and the battery button was torn (probably my deed though it must have been waiting for the hit to get disconnected). Fixed it and it now works again inside that torch...

====================================================== Dimiter Popoff, TGI

Should be written on case. With so many coming and going, it probably won't be much use if there's an attempt at subsequent purchase, by brand name, in the future.

Do these still have a separate micro-USB charging port, or is this interface internalized between the two normal functional battery case terminals?

I'd be interested to know what the performance is like in a series connection at EOD (end of discharge). It's going to happen to one cell before the other(s).

Does the cut-off cell provide continuity to the remaining circuit? Voltage drop (reverse) under those conditions?

RL

I opened the torch but the one with the original coating says nothing about any brand... (I was surprised, too). Here is the aliexpress page where I got them (October this year):

All of the mentioned have a USB-C port and at least some of them have a LED flashing or something while connected to USB, I think it would stop flashing when charged, the light got continuous.

The multimeter stopped abruptly (no "low battery" indication), which is expected. I think I had the same with the torch (great when it happens during a blackout...). No idea on the continuity etc., did not look into that.