Nano 3.0v charger to charge 3.7v RCR123?

[dealgrabber2002]

I know it's dangerous to use 3.7v charger to charge 3.0v RCR123. What happens if I use Nano 3.0v (single bay) to charge a 3.7v RCR123?

I am sorry if this already been asked. I used the google search, but couldn't find anything similar to my question. Maybe I am just really sleepy and over look it.

Thanks in advance.

E

 

[mdocod]

actually, in many cases, it is more dangerous to use a 3.0V charger to charge 3.7V cells, especially if it is designed for 3.0V voltage regulated cells.

Currently, there are 2 kinds of 3.0V cells.

1. LiFeP04 3.0V cells, which are actually bare 3.2V cells being pawned off as 3.0V cells for the convenience of not having to explain anything to consumers. Their charge termination should be somewhere around 3.6-3.8V.

2. 3.0V "regulated" cells that are actually 3.7V liCo cells that have a voltage reducing Diode in the circuit usually accompanied by a PCB. These cells actually require ~4.4V charge voltage to be completely charged because of the circuit in them.

If you use a charger for cell #1 above to charge a LiCo (3.7V cell), you will only charge it to about 20-40% full capacity.

If you use a charger for cell #2 above to charge a LiCo (3.7V) cell), you can expect a chance of explosion in your afternoon forecast.

Eric

 

[dealgrabber2002]

thanks. lucky you info me. At first I just thought by using 3.0 to charge 3.7 will not fully charge it. I didn't expect it to be that dangerous.

Thanks.

 

[hank]

> LiFeP04 3.0V cells, which are actually bare 3.2V cells
... charge termination should be somewhere around 3.6-3.8V.

That's a relief, I think, I got a couple of those (Ultrafire 15270, smaller than RCR123) that came with a Nano "NBC-A001" charger (AAA size with a slug, label says DC Out 4.2v.)

I measure about 3.45v on fresh charged cells taken off right as the indicator light turns from red to yellow to barely green -- couldn't figure out what was happening.

 

[mdocod]

> LiFeP04 3.0V cells, which are actually bare 3.2V cells
... charge termination should be somewhere around 3.6-3.8V.

That's a relief, I think, I got a couple of those (Ultrafire 15270, smaller than RCR123) that came with a Nano "NBC-A001" charger (AAA size with a slug, label says DC Out 4.2v.)

I'd just measured about 3.7v on a charged cells right after the light turned green and couldn't figure out what was happening.

The NBC-A001 is for use with 3.7V LiCo (or some LiMn) chemistry cells, using it to charge LiFePO4 is just going to overcharge the cells. During charging, the voltage probably did rise to ~4.20V, and then it settled down to ~3.7V after the charge was terminated.

This does work, and with LiFePO4 cells, there isn't anything unsafe about doing this, but you are likely to reduce your cycle life pretty substantially in doing so.

You need to get a charger designed for LiFePO4 chemistry cells if that is what you are charging.

 

[hank]

Thanks MDOCD -- that's why I gave the model number off the charger!

-- that Nano charger is packaged as meant for 3.0v, and was sold bundled with those cells identified as 3.0v iron phosphate (from a US web vendor known here -- hey, I should've waited for AW, I know ....).

No surprise to find labels on any lithium cell, or charger, are dubious. It's early days with this stuff, that's why we worry.

Can you point me to a reference source on model numbers of Nano chargers?
Any specifics on what I can measure if anything?

I'll follow up -- I'd like to be able to point to info from Nano if it's available anywhere when I contact the supplier.

 

[mdocod]

Thanks MDOCD -- that's why I gave the model number off the charger!

-- that Nano charger is packaged as meant for 3.0v, and was sold bundled with those cells identified as 3.0v iron phosphate (from a US web vendor known here -- hey, I should've waited for AW, I know ....).

No surprise to find labels on any lithium cell, or charger, are dubious. It's early days with this stuff, that's why we worry.

Can you point me to a reference source on model numbers of Nano chargers?
Any specifics on what I can measure if anything?

I'll follow up -- I'd like to be able to point to info from Nano if it's available anywhere when I contact the supplier.

If it was packaged with 3.0V cells, then it is very likely that I have mislead you on this one...

It is possible that both the 3.7V and 3.0V models of this charger are sharing the same model number. I just did a quick search of the model number and pulled up a 3.7V nano and made the assumption that the model number would be correlated to the cell type it's designed for, with a different model number of a different charging style...

We all get into trouble with assumptions some times

With that in mind, it still would not be a bad idea to figure a way to hook up a multi-meter while the charger is charging the cell, so you can see what the voltage is rising to during the charge just to make sure that your charger is appropriate for those cells. It should turn green somewhere around 3.6-3.8V, ideally not too much higher for the sake of the cells life...

Eric

 

[hank]

I can put a meter in place of the slug provided to fill the gap between the battery and the charger terminals -- is that what you mean? I've got a cheap little meter -- just set it for the 20 volt range and check that right around the time the light turns green?

 

[mdocod]

I can put a meter in place of the slug provided to fill the gap between the battery and the charger terminals -- is that what you mean? I've got a cheap little meter -- just set it for the 20 volt range and check that right around the time the light turns green?

yes.

 

[hank]

Okay, I'm baffled. Still the NBC-001, labeled as a 3.0v charger.

Cell sold with the charger is a short little RCR2 Ultrafire "TR-15270 600 mah 3.0v"
(green shrinkwrap printed "Warning: the voltage of full charge ... is 3.6V")

3.84v measuring across the charger terminals (no cell in place)

0.5v measuring with the cell in the slot, bridging the gap with the voltmeter probes.
(Oh, wait -- did you mean put the probes on either end of the cell while it's charging? I was checking from the +terminal of the charger to the +terminal of the cell, or the - terminal of the cell to the - terminal of the charger. Doing that, the voltage measured drops as the cell's voltage goes up; that makes sense I guess)

Checking the cell itself is at 3.3v, at this point.

(up to 3.45v on the cell, and down to 0.45v from cell to terminal of the charger, a bit later)

This is powering an old Arc LS (aftermarket battery case). The light starts to flicker before the cell drops near the 2.0v.

I'll sit here with the fire extinguisher and gas mask handy til the light turns green and measure it again. ....

Ok, green light, cell measures 3.67v; measuring between + terminal on the charger and +terminal on the cell shows 0.2v.

Anything else I ought to be measuring with my $8.98 meter here?

Advice welcome on what kind of cells I should be using with this charger, and what kind I should NOT be using.
(and where to buy them, too)

 

[mdocod]

Sounds like the charger is a LiFePO4 chemistry charger, everything sounds fine. Provided the RCR2 cells you have are definitely LiFePO4 then everything sounds perfect. 3.8V open circuit on the charger sounds perfect for a LiFePO4 charger. (yes, I meant to measure on either side of the cell while in the charger )

No need for a fire extinguisher with LiFePO4 really, hehe...

Eric