hand-held DVMs and rechargeable lithium 9V or 1.5V cells

Are you thinking that a 9v lithium battery damaged a DVM being used to measure its voltage?

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It's not the battery technology, it's the internal BMS:

Battery Management System (BMS) Conflicts: Modern lithium batteries have a BMS that may disconnect the battery during a high-voltage event to protect the cells. If the BMS "opens" the circuit to save the battery, the transient is no longer being clamped and will hit your downstream electronics at full force.

And then this safety info:

Safety Hazard: Repeatedly forcing high-voltage spikes into a lithium battery can cause degradation or even thermal runaway if the energy is high enough to damage internal separators.

Better Alternatives For reliable transient suppression, use dedicated components designed for speed and energy absorption: TVS Diodes (Transient Voltage Suppressors): These react in picoseconds or nanoseconds to clamp voltage at a precise level. MOVs (Metal Oxide Varistors): These are cheap and effective for high-energy surges, though they can wear out over time. Surge Stoppers: Specialized ICs like the Analog Devices LT4356 can actively isolate and regulate voltage during a spike.

-Google AI

No.

I'm thinking that a non-clamping battery may allow a DVM to be damaged, due to not-functioning transient protection.

RL

So you propose to put TVS diodes across lithium batteries?

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I'll probably consider doing that in the supply pins of the parts that have failed.

As I've mentioned, the pcb routing is pretty silly, and the range switch panel holding these parts may be it's own worst enemy.

There are no schematics for a Mastech manual meter using the ICL7129 (completely different pinout from ICL710x) - and it uses no quad op amps (only duals) in anciliary functions - nor does it marshal a 'beeper', though this is a 'free' pin function on the chip.

Anyways, something to keep in mind as a possibkle problem using rechargeable lithium substitutes.

The charged voltage of the PP9 variety is 8.4V, suggesting that it may actually be two cells and not a single cell with a boost regulator. Charging limit per Li polymer cell is typically <4.2V.

If that's the case then surge absorption behavior may be normal for this particulsr type. For AAs, it's a buck regulator.

RL

You'll find no BMS, as such. in these batteries ($).

Google AI 'my ass'.

RL

I have about 12(?) assorted electronics instruments (multimeter, LRC meter, sound level meters, clamp ammeter, IR thermometer, etc) that use 9V batteries. Over the years, I've replaced the original 9V alkaline batteries with various forms of Li-Ion 9V batteries. They are divided between 9V with an external charger and those with a USB connector and internal micro USB and USB-C charger connectors. My guess(tm) is the upgrade process has been going for about 4 years. Most of the 9V batteries were made by EBL.

So far, I've had 2 battery failures. Both failures were dead on arrival and were not installed in an instrument. I did have one instrument die, which used a 9V battery. However, that one had an alkaline battery. Offhand, I would say that 9V Li-Ion batteries work quite well and do not blow up meters.

I've had little experience with AA and AAA Li-Ion batteries in instruments. At about $7/ea for AAA or AA, it's too expensive.

Incidentally, what I like most about Li-Ion powered instruments is that the batteries have a very low self-discharge characteristic. They lose about 15% of full charge almost immediately, and stay there nearly forever. Even if I haven't used my various instruments for a year or two, it's ready to use. That's a major improvement over having to install fresh batteries (and clean out the potassium carbonate mess) before the instrument is again usable.

I don't know what killed your Mastech M1000 meter. In my limited experience, I've seen far more meter range selector switch contact failures than active component failures. My most common failure was voltmeter overload caused by radical over-voltage inductive spikes, while measuring the battery voltage on an older automobile and starting the engine.

I've had good luck with AMZN Basics here.

I've had lots of trouble with dead-on-arrival lithium coin cells, and find that direct load testing is essential. We may have discussed this. Anyway, for 3.7 Volt coin cells, one tests with 10 Kohms (unloaded) and about 400 Ohms (pulse load) and compares with the battery datasheet guarantees.

The failures are not random. Usually if one cell in a batch fails, most of them do. This pattern suggests improper storage in a very hot warehouse.

I've had good (but not perfect) luck with AMZN Basics.

I spend the money anyway, because they don't leak even when quite old, so fewer expensive and perhaps irreplaceable instruments or tools are destroyed.

Yes.

There is a lot of power in those surges, so a pipsqueak voltage clamp will vanish in a puff of magic smoke.

Joe

I think that a Duracell or Energizer alkaline lasts about twice as long as an Amazon battery, and is less likely to leak.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

"Finally! A Battery That's Better Than Energizer And Duracell!"

I have a West Mtn Radio CBA-II discharge tester:

If you're interested in Li-Ion batteries, chargers, and LED lights, I suggest looking at:

Also see:

Critical Risks of Using Bare Cells Operating lithium batteries without any BMS (either internal or external) is extremely dangerous for several reasons: Fire Hazard: Without a BMS to cut power, overcharging can lead to thermal runaway, causing the battery to swell, catch fire, or explode. Permanent Damage: Draining a cell below its safe voltage limit (typically 2.5V) causes irreversible chemical damage, after which it may never charge again. Cell Imbalance: In multi-cell packs, some cells will naturally charge faster than others. A BMS balances these so one "bad" cell doesn't compromise the safety of the entire pack.

Verdict: While you can buy lithium batteries without an internal BMS, they almost always require an external management system or a highly specialized charger for safe operation.

-google AI

The off-the-shelf AAX and Type N types almost certainly have an internal BMS, otherwise they wouldn't be for sale to the general public.

I was talking about Lithium. I can buy good ones locally. But Lithium has been a problem. But across the board, alkkaline is more likely to leak and destroy when forgotten than Lithium.

Joe

I'll look these over. Thanks,

Joe

I see a lot of gadgets that use solar power, or some weird energy harvesting thing, when they could run for 20 years on a Tadiran primary lithium battery.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Not quite accurate. Deep discharge increases the risk of dendrite formation. These can then pierce the separator causing a short circuit. The internal BMS in many cells will prevent further use if deep discharge has happened.

I like the 'almost certainly" part, in response to the 'BMS as such'.

You could go on for days without ever addressing the specific issue of the commodity-packaged rechargeable Lithium Ion cell construction.

They have to have buck (<4V2) or boost (<8V4) converters to recharge from micro-USB (5V,<2A hardware present on their shells). Without either opening them up or referring to the specific mfrs drawings, both of us are just blowing smoke.

If I get to the stage where there are extras floating around here, or dead ones start popping up, I'll know more, unless somebody else gets there first and reports their findings.

A thermal or other type of fuse does not constitute a BMS.

RL