RCR123/16340 - Why varying voltages?

[rufus001]

I have Tenergy 3.0V, Ultrafire 3.6V and Soshine 3.7V rechargeables that all charge to around 4.1V. So what's the point of the different voltage ratings? If the Tenergy 3.0V was a rechargeable for lights that can't handle 4.1V then fair enough. But given that it recharges to 4.1V isn't just as likely to blow a light as the other two batteries? Or is simply that the Ultrafire and the Soshine hold the higher voltage longer that they are given a different rating? Oh so confused!

Also I got battery chargers with the Tenergy and Ultrafire that state not to charge the batteries in any other charger. Is this correct or are they spinning a tale and I can simply use my Soshine for all three batteries?

 

[AnAppleSnail]

3.6 or 3.7v is a nominal voltage. Most Li-Ions range between 3.2v and 4.2v when happy. You can put almost any diode in series with a cell to make a lower-voltage rechargeable battery, but the diode burns (Voltage drop x current) watts of heat right next to your lithium cell. This is dodgy stuff.

There are a few Li-Ion chemistries (LiFePO4 or something) that are 3.2v nominal, which can be used in "RCR 123 only" lights under some circumstances. If you blow it up don't blame me though.

"Use no other chargers" is partly liability. There are some CRAP chargers out there. Some are 4.2V +/- 0.1v voltage sources, not real chargers. Eugh.

 

[HKJ]

There are generally 3 different LiIon batteries:
3.6/3.7 volt, that must be charger with a 4.2 volt max. charger.
3.2 volt LiFePO4, that must be charger with a 3.6 volt max. charger.
3 volt, made from 3.6/3.7 volt cells and a diode, these must be charged with a special charger that is around 4.6 volt max.

Using the wrong charger for any of these batteries is a problem:
Using to low voltage on the charger will no charge the battery to full capacity.
Using to high voltage might make the battery explode.

 

[45/70]

Hi rufus. If you search the Forum for "3 Volt RCR123", or something along those lines, you will find a few threads about the different "3 Volt" cells. The Tenergy, and Soshine "3 Volt" cells are LiCo/ICR cells with diodes installed under the positive nipple. The purpose of these diodes is one of them lowers the voltage under load to closer to 3 Volts, and the other diode allows the cell to be charged (diodes only allow current to flow in one direction, hence the need for two).

When you measure the voltage of one of these type cells when fully charged, depending on the quality of the meter used, it will read somewhere between 3.8 and ~4.2 Volts. This depends on the internal resistance of the meter used. Also, these cells necessitate the use of a special charger that uses a higher voltage, typicaly 4.4-4.5 volts, again because of the diode that allows the cell to be charged. The charging voltage must be high enough to allow 4.20 Volts to reach the cell behind the diode. For this reason, you do not want to charge "normal" cells with one of these special chargers. It will inevitably end up over charging a normal cell to possibly dangerous voltages, or at the very least, damage the cell.

I see there have been some replies already. Anyway, these "3 Volt LiCo" cells are not to be confused with "3 volt" LiFe/IFR cells either, as these charge at a much lower voltage. As HKJ said, there are three (actually four) types of 16340 size cells. The LiCo and LiMn charge with a 4.20 Volt CV, LiFe with 3.6 Volts, and the LiCo cells with diodes at 4.4-4.6 Volts.

Dave

 

[rufus001]

Thanks Guys! I've done some more reading as 45/70 has suggested but there is one thing I'm understandably rather cautious about. It appears these(3V) are designed to be a rechargeable alternative to the CR123's for lights that can't handle the extra voltage of the 3.7V rechargeables. One problem. I want to use them in my Spark SL6-740NW and I can't find an operating voltage for this torch anywhere but it states on their website that 2XCR123's can be used. So the problem is does the diode definitely restrict the voltage to CR123 levels? Or is it "near enough" which in the Spark's case may actually be too much? And then I blow my torch ... again.

 

[Shadowww]

For that Spark, wouldn't you be much better off just using a single 18650?

 

[rufus001]

For that Spark, wouldn't you be much better off just using a single 18650?

I'm on my iPhone so I can't find the link quickly but I think the CPF review shows better output on 2 batteries hence my attempt to find 2 rechargeables.

 

[rufus001]

I just checked the reviews and this light is actually perfectly regulated with a 18650. I have seriously gotten this light confused with another one. Sigh!

 

[45/70]

I think Shadowww's suggestion is the way to go, but to address this,

......So the problem is does the diode definitely restrict the voltage to CR123 levels? Or is it "near enough"

The LiCo cells with diodes discharge at a very similar voltage to LiFe/IFR cells. There's practically no difference. That said, the voltage during discharge is generally somewhat higher than CR123A primary cells (which are nearly always under 3 Volts, under an actual load), usually being in the ~3.2 Volt range. Some lights can handle this, and others can't.

I also should have mentioned that Tenergy also provides "3 Volt" LiFe/IFR 16340 cells. As I remember, the LiCo "3 Volt" cells are blue print "900mAh" on the label, and the LiFe are green print "750mAh", neither of which is actually correct, but anyway. A lot of folks mix these two up when it comes to chargers. Each must use the charger that came with the cells, or the cells will not be properly charged. Of course a "normal" 4.20 Volt LiCo charger won't work for either type. It won't fully charge the "3 Volt" LiCo cells, and will overcharge the LiFe cells.

Dave