Tenergy RCR123A 3.0V LiFePO4 test data

[Probedude]

I bought this set from All-Battery about a month ago.
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1877

2 of the cells I received were pretty much dead. The other 4 were good.

I charged up the 2 dead cells, left them on the supplied charger for ~ 4 days then discharged them. These are cells 1 and 2 on the attached graph.

This past week I took 2 of the good cells and left them on the charger and just now discharged them on the CBAII (cells 3 and 4 on the graph).

Discharge current on all 4 cells was 700mA (~ 1C for these 750mAH cells).

Very poor capacity compared to their rating. The online spec says that discharge should be limited to <550mA so I'll redo the discharge at 500ma and see what the capacity measures.

 

[SilverFox]

Hello Probedude,

:devil: It is good to see that they are all "consistent..." :devil:

Consistently below their rated capacity, that is...

Tom

 

[Probedude]

Hello Probedude,

:devil: It is good to see that they are all "consistent..." :devil:

Consistently below their rated capacity, that is...

Tom

Yeah, you'd think I'd learn my lesson.

 

[BMF]

Oh no, I got the same set at the beginning of the year. I don't have anything to test so I didn't know about this. What do I need to do when don't have equipment to test?

 

[Fallingwater]

I charged up the 2 dead cells, left them on the supplied charger for ~ 4 days then discharged them. These are cells 1 and 2 on the attached graph.
This past week I took 2 of the good cells and left them on the charger and just now discharged them on the CBAII (cells 3 and 4 on the graph).

You left the cells for days at an end on a cheap charger that's very likely to slowly overcharge them, and you're wondering why their performance sucks?
The LiFe chemistry is more tolerant of abuse than LiIon, but I'd say days of overcharging are likely to hurt it too.

 

[jzmtl]

You left the cells for days at an end on a cheap charger that's very likely to slowly overcharge them, and you're wondering why their performance sucks?
The LiFe chemistry is more tolerant of abuse than LiIon, but I'd say days of overcharging are likely to hurt it too.

That charger looks like the same thing as my ultralast, it seems to be a smart charger.

 

[Probedude]

That charger looks like the same thing as my ultralast, it seems to be a smart charger.

Yep, it's CC/CV. It's not merely a CC NiMH/NiCd charger. It tapers very very slowly to the CV output which is why I left it on for days - that and these days that's about when I catch a breath of fresh air and can get back to my projects.

My Tenergy Sub-C 3800 packs only measured ~2800mAH
My Tenergy 2600mAH AA's only measure ~ 1600-1800mAH. The 2300 cells I had before from them had more capacity than their 2600 cells!

You've seen what these RCR123A's measure.
My DX RCR123A 3.7V cells only came up to ~380mAH instead of 800mAH.

A lot of vendors overstate capacity and/or their cells are of variable quality even within a model.

On the other hand my Eneloops have amazingly been extremely close if not spot on in capacity and are well matched with each other.

 

[jzmtl]

I don't know about days thou, mine shuts off (at least the light turns green) when cells are charged in a few hours.

 

[Fallingwater]

Most cheap "smart" chargers keep delivering a trickle of power to the cells even when they are supposed to be inactive, which is why it's wise to disconnect them as soon as possible after the charge is finished.

 

[Probedude]

Most cheap "smart" chargers keep delivering a trickle of power to the cells even when they are supposed to be inactive, which is why it's wise to disconnect them as soon as possible after the charge is finished.

This isn't true of Lithium battery chargers.
Lithiums do not gracefully handle overcharging which is why a properly designed lithium charger uses constant current AND constant voltage charging, even the cheap ones.

This isn't a NiMH or NiCd charger. In constant voltage mode the current flow will drop to zero and stay there unless the voltage setting is too high. There is no trickle charging.

I don't know about days thou, mine shuts off (at least the light turns green) when cells are charged in a few hours.

Mine does this too. All the red led does is show that current is flowing into the battery. The brightness of the red LED is proportional to the current flowing.

Here's info on charging lithium batteries.

http://www.batteryuniversity.com/partone-12.htm

Dave

 

[Fallingwater]

I'm well aware of how LiIon cells and their chargers work, yet I insist: many LiIon chargers charge to 4.2, then turn off their charging leds and supposedly shut down, yet if you leave cells in them for several hours after the charge is complete they'll read more than 4.2V when you get them off. My own cheap charger (which I used before buying my RC one) certainly did this.

LiIon cells do not spontaneously erupt in a ball of fire if charged to slightly more than 4.22V or thereabouts(IIRC the thermal runaway voltage is about 4.6), but if they are left in a cheap overcharging charger for several days, they might well be ruined in the end.

Now I don't know if this applies to LiFe as well, but if it does it could be a reason for the lousy performance.

 

[mdocod]

These capacity measurements fall right in with what they should be for a LiFeP04 cell of that size, there is nothing weird going on here other than overstated label capacity. It is well known that LiFeP04 commonly has about half the energy density of LiCoO2, so if LiCo02 cells are performing in the 500-600mAH range, one should expect about 250-300mAH from LiFeP04 cells. Expecting more is a pipe dream that should be left for people who waste away trying to get their over-unity device working.

 

[NA8]

Just for reference, how do AW's 500mAh LiFePO4 cells hold up compared to these ? 500mAh or considerably less ?

 

[mdocod]

AWs are no different, ~300mAH under realistic loads. I remember a graph of their discharge behavior somewhere but can't find it now...

 

[Probedude]

These capacity measurements fall right in with what they should be for a LiFeP04 cell of that size, there is nothing weird going on here other than overstated label capacity.

Thanks for the info.

Dave