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I have these two batteries, 18350 form factor, without any label. As far as I know they are rechargeable because I've salvaged them and put in my salvaged "li-ion to be cecked" box. Now I've completely forgot where I took them and they doesn't seem to be li-ion.

They were at 2.7V more or less, then not too low to be used if li-ion,but then I've tried to charge them with my li-ion charger at 0.1A and the charger blocked the charge because no current were delivered. I thought they were already fully charged (quite strange, since they were in this box since january) and in fact after 24h they show 2.85V.

There's a way to understand which kind of batteries are them? PS: I can charge/discharge under constant load/voltage and log the current/tension. (in a safe container, of course)

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  • \$\begingroup\$ Not all Li-Ion batteries are rechargeable. Did you try to compare them with 123A-type "photo batteries"? \$\endgroup\$ – Ale..chenski Sep 12 '18 at 17:19
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    \$\begingroup\$ @OlinLathrop: I'm deeply sorry to have hurted your delicate eyes, it was an inconsiderate imprudence of me considering that such a sensitive public could read my question. Anyway, an intellectually honest AND intelligent person should downvote my question because of "unknown": if it's unclear the person can't be defined intelligent, if it is clear indeed it's not intellectually honest. PS for the sensitive ones: I've edited the question. \$\endgroup\$ – theGarz Sep 12 '18 at 17:54
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    \$\begingroup\$ @Ale..chenski: actually the voltage could indicate a slightly discharged 123A, but anyway the form factor can't determine the chemistry. \$\endgroup\$ – theGarz Sep 12 '18 at 17:59
  • \$\begingroup\$ The CR123A cells (size 18350 or 17335) were used in photography for decades, and 2.7 V is typical voltage for them, powerstream.com/cr123a-tests.htm 2.7 V for rechargeable Li-Ion for six month is a death verdict, if they don 't charge, it means they are not rechargeable or dead. Throw them away and get new ones of the type you need. \$\endgroup\$ – Ale..chenski Sep 12 '18 at 18:37
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    \$\begingroup\$ @TheGarz Welcome to EE.SE! Don't worry about Olin. He seems to periodically rub people the wrong way, but look at his profile. He has given us 5558 answers, and he has asked only 5 questions, two of which were so useful to the community that they are each worth more than double my ~2 month account. The same is true of many of the actual engineers and top contributors. You're not obligated, but please be as patient as you can when the engineers are frustrated and try to assume good intent. At the same time, engineers, please be as kind and patient as you can stand. We're doing our best. \$\endgroup\$ – K H Sep 15 '18 at 19:19
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This could be due to a problem in your charger's constant current mode operation. May be you can try increasing the 0.1A current limit to a higher value like 500~800mA. Also monitor the voltage and current externally.

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  • \$\begingroup\$ Ok, i'll try 300 mA but i've already charged (actually rechargable) batteries at 100 mA with the same charger without issues... \$\endgroup\$ – theGarz Sep 12 '18 at 18:02
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CR123 is 2/3 the size of an A size battery. (Type A batteries are obsolete). And a CR123 is a primary battery that cannot be recharged.

A rechargeable CR123 should be referred to as an RCR123.

The RCR 18350 battery is not really a replacement for CR123. The RCR123 has a 1 mm larger diameter than the CR123. Typically a diode is added in series with the Li-ion 18350 battery to drop the 3.6V by about 0.7V.

Other Li-ion battery chemistries (e.g. LiCoO2 (ICR) or LiMn (IMR) chemistry) can be used without a diode as well. A 3.0V-3.2V LiFePO4 (IFR) Li-ion can be used becasue it is less vulnerable to over charging but is a horrible replacement.

See Types of Li-ion

Some RCR123 batteries do not have the protection circuit, and as a result, will not be compatible with many chargers. Li-ion chargers should use a protection circuit because LI-ion batteries have a tendency to start on fire and explode when misused.

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enter image description here

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    \$\begingroup\$ You still don't offer any method on how to identify the unknown battery type. \$\endgroup\$ – Ale..chenski Sep 13 '18 at 21:08
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For starters, you should post a photo of your battery in question, to see what kind of tabs or other connector does it have. It might give some clues.

Second, you should try to refresh your memory and provide some idea of where these two cells came from, how old the equipment was (it might narrow the identification and exclude new commercial developments).

Generally if this is a CR123A non-rechargable cell and it has 2.7 V, it is nearly discharged. However, when attempted to "charge", it should consume full charging current and its voltage should creep up a bit. The charger should not disconnect. It also should be able to drive moderate loads (say, 100 Ohms) for measurable time.

If you report that your standard Li-Ion charger gives up (I would guess very shortly, in a fraction of a second), it is likely a dead Li-Ion cell which has all internals vastly deteriorated, has nearly zero capacity, and developed a very high ESR, such that the charger voltage immediately goes above 4.3 terminal voltage, and charger disconnects. To check if this variant is true, you should apply a moderate load (100 Ohm), and see for how long it will keep the 2.7 V level, if ever.

Again, if your cell doesn't charge and has no capacity, throw it away.

If it holds some charge and has 2.7 V, throw it away as well.

So, you have only one outcome :-)

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