Running a pair of 16340 cells at 1.4 A

[Black Rose]

I've got a couple of those 7.4V 10W incan drop-ins available at DX, etc. (mine came in my SpiderFire X-03 hosts)

I've been running them with a pair of TrustFire protected 16340 cells.
The cells are labelled as 880 mAh but are really only around 600 mAh each.

I decided to see what the current draw was for the drop-in with the pair of cells and was surprised to see that it was 1.4A.

I have a pair of AW protected 16340 cells, but I haven't taken a measurement with those yet, but I am expecting similar results.

Is it a good idea to run protected 16340 cells with that kind of a current draw?

 

[lolzertank]

LiCo cells shouldn't be drained at a rate over 2C, which in the case of 600mah cells would be 1.2A. Maybe it's time to buy some IMR16340 cells? Those can handle 8C or about 4.4A.

 

[Black Rose]

I just tested it with the AW 16340 cells and got a reading of 1.44A.

I'll have to figure out how heavily I want to invest in incan drop-ins and then pony up for some IMR cells.

 

[ma_sha1]

I am running the 15W version DX drop-in on 2 ultrafire RCR123,
works fine.

 

[mdocod]

It will work fine, but for how long and at what risk?

For the purpose of making a point, I used an EO-9 (2 amps) with a pair of AW protected RCR123s for a few months a long while back. I limited continuous runs to mostly short bursts, and always charged after a few minutes of use. The cells are several years old now and still work pretty decent to this day.

On the other hand, if you used the same configuration, but with lots of continuous runs, and full depth cycles, the cells would likely not last longer than ~25-50 cycles.

High current abuse on li-ion is like any other abuse, each abusive factor for the cell adds up to the sum total of wear and tear, combined with natural aging, that all increase the risk of the cell developing internal shorting and thermal runaway.

1.4A is pushing it, but if used almost entirely in short bursts and with frequent recharges, the likelihood of having an explosion as a result of that behavior is probably pretty low.

A pair of IMR-16340s are cheap, and drive incans better than LiCo cells in this size class IMO. If you think you are going to keep running this configuration, get the IMR cells, if this is just a 2 week fling, I wouldn't bother.

-Eric

 

[Black Rose]

Thanks Eric.

That's what I needed to know :thumbsup:

 

[mudman cj]

Another factor that hasn't been mentioned yet is that IMR cells will give more runtime at this current. For example, AW's black "high current" R123 cells rated for up to 1.5A have a measured capacity of 255mAh at a 1.5A rate from Silverfox's testing, while AW IMR 16340 cells have a measured capacity of 510mAh at a 1.5A rate. So, you can double your runtime and increase safety by switching to IMR cells.

 

[Bullzeyebill]

For those who do not want to mess with LiCo CR123's the IMR seem the best way to go. I will still be using my Powerizer's, monitoring closely, and they are strong cells at almost 4C, (SilverFox's graph) though I am not using them at or anywhere near that current.

Bill

 

[Black Rose]

A related question:

When I tested the TrustFire cells, I got 1.4A. The AW cells deliver 1.44A.

Is this related to the internal resistance of the cells?

 

[45/70]

I would say so, Black. I'm sure you would see slightly different current draw with different pairs of cells, even from the same brand and batch. The state of the cells charge, temperature etc. would also make a difference.

Dave

 

[Black Rose]

Well it appears that using my Trustfire 16340 cells with the 7.4v incan drop-ins, even for short bursts, has started to have a negative effect on them (or they are showing why they are budget cells).

They used to come off my WF-138 at 4.15v - now they come off at around 4.09v.

EDIT: I decided to run the cells down with an LED P60 drop-in drawing 1A.
Cell #1 was at 3.5v when the protection circuit on cell #2 tripped and turned the light off.

After charging, cell #1 is 4.04v and cell #2 is 4.05v

 

[mdocod]

Sounds like they are headed down hill..

You've probably run across the other posts I and others have made on the subject of the WF-138/139 chargers, which have a less than desirable charging method. It's possible that the cells might hold a higher voltage off the charger if the charger were using a true CC/CV method, as compared with the "CC-only" that often trips the PCB in the cell before the cell has reached 4.20V resting.

I guess the point I am making, is that, while the cells are definitely showing some wear and tear. It *might* not be *as* bad as it looks based on end-of-charge results on that particular charger.

I would still recommend leaning to the side of caution and keeping an eye on them.

3.5V for one and the other terminating on the PCB says to me that the cells are still within ~5-10% of each-other capacity wise, so that's not too bad.

 

[Black Rose]

Yeah, the WF-138 is not the optimal charger, but since I can't safely charge my 16340 cells on my pair of Yoho-122 chargers, it'll have to do until I decide if I want to get a hobby charger setup that can deal with the various cells that seem to be multiplying like rabbits around here

As a check of the charger, I did the same test with the P60 LED drop-in with my pair of AW 16340 cells to drain them so I could do a full charge instead of a top-up.
After I charged them up, they ended up with a resting voltage of 4.13v.

I'll just have to take some extra care with the Trustfire cells when using them.

 

[Black Rose]

I recently picked up a great deal on some Lumens Factory SR-9 drop-ins in the Marketplace.

Running them with the same Trustfire 16340 cells, I am getting a reading of 1.17A, so they seem to be within the 2C window.

Now that I've discovered the joy of incans, it's time to invest in some IMR cells.