Large Scale Central

Poor preforming LiIon batteries.

Electronics Power and Sound
#21

@Michael Glavin - a quick question if I might as I think it relates to this thread. I have a 4 cell 220Mah pack that I built 1 year ago that was performing properly. I failed to keep it charged while stored for 10 months and when I went to freshen it up it will not take a charge. My Tenergy Balance Charger says it’s not even connected. I opened it up and did individual cell voltage checks. All cells are under .5 volt, some cells are under .25V. The smart charger won’t even charge individual cells.

In your experience, what is the minimum voltage a cell can be drawn down to before it is irreversibly damaged?

I might be able to force some charge on to these cells using a single cell PCB and a dumb charger, but if the cells are toast I won’t bother.

#22

Procedure given to me by the Sanyo agent here in Australia.

For 14.8 volts (4S), just use a fused regulated 15 volt DC supply such as a computer power supply for a few minutes to force a bit of voltage so the smart charger can recognise the pack.

Obviously the polarity must be correct.

#23

That might help Tony. Even the dumb charger doesn’t see enough to start the charge, even on a single cell.

Rooster - get ready with that nuke pic (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-yell.gif)

#24

John,

I don’t have much experience with attempting to revive overly discharged batteries or for that matter a “KNOWN” it will be okay voltage reading… 2.5V per cell is typical cut-out voltage recommendations. I have seen cells @ 1.8V or better cycled, load tested that worked with some diminished capacity. How long they lived thereafter I don’t know as they were not my batteries. Since were dealing with NON volatile situations if your power system fails (unlike aircraft) I can see the merit in rolling the dice and utilizing a resurrected battery.

As suggested hammer it for a few minutes or so at 14.0-16.0V/2A and see what happens. DO NOT WALK AWAY AND MONITOR CELL TEMPERATURES. Some suggest all Li-Ion cells are 3.7V whereas most OEM data sheets suggest their 3.6V. Lithium cells don’t need to be fully charged, close is BEST for long life. I’m confident (but not 100% sure) your Tenergy charger has a screen for Li-Ion cells. You’ll note it sees them as 3.6V per cell, use this regimen always! IMO 3.0V-4.2V is safe well established baseline operating range for your 18650 Lithium Ion cells.

If your successful burping the cells (success would be reading about 2.5V + voltage of each cell individually). Use the balance charge regimen to completion, then discharge cycle the battery and recharge for a couple of cycles, again your charger can do this automatically. I wouldn’t be surprised to record a 20% or better loss of capacity.

FWIW: If you were to find a discharge graph for Lithium cells you’d note how steeply voltage falls off the chart, once you realize approximately 3.2V the voltage starts falling nearly straight down within seconds IME. I used Lab equipment (Oscilloscope, PC controlled power supplies and electronic loads) to evaluate these batteries for several years (seems like a lifetime ago) yet I stayed within published safe voltage recommendations when evaluating same. Voltage cut-off @ 3.0V per cell nets about 95% of the cells capacity.

PCB’s are generally rated for cut-out @ 2.5V per cell. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif)

Michael

#25

Thanks Michael. I’ll try and “burp” them over the next few days and report back here. I’m pretty sure these cells were not first quality, or at best not well matched as I have other packs of the same brand that are older and have been left to sit on the shelf for too long that did not self-discharge to this extent - they all charge up fine.

#26

Good info guys.

Terry I had bought a bunch of batteries from all battery over the last few years. I think two died on me but might have been my own fault. At the price I got them for it was easier to toss them. Im sure if I spent more I probably would not have had that problem.

Joe you really cant beat the Li-ions because they hold their charge for a long period of time. I tried the others and after sitting a month or two the charge was down. No such thing as getting something out fast to run. Plus the size. I can fit a Lith battery pack under my Forney coal bunker without any modifications.

#27

Shawn Viggiano said:

Joe you really cant beat the Li-ions because they hold their charge for a long period of time. I tried the others and after sitting a month or two the charge was down. No such thing as getting something out fast to run. Plus the size. I can fit a Lith battery pack under my Forney coal bunker without any modifications.

I didn’t know live steam engines required batteries! (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif)

#28

Ah, for the RC system they do. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

#29

David Maynard said:

Ah, for the RC system they do. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

David,

Of course you are right. Doh, why didn’t I think of that! (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-sealed.gif)

#30

“Burping” the pack seemed to work and allowed my dumb charger to get some juice into it. I didn’t have a 15V power supply. The closest I could find was an old Western Electric AC Wall Wart rated 15-18VAC @ 2.5A. I connected it to a full wave bridge and was getting about 25VDC with no load. I connected the pack and the load brought the voltage down to just over 5VDC. I kept monitoring voltage and temperature as the voltage slowly climbed. When it got up over 8V (maybe 10 minutes) I moved the pack to the dumb charger where it is still taking current and voltage is getting close to 14.

Once the dumb charger finishes (PCB cut off) I will move the pack to my balancing charge and run a discharge cycle then a few balance charge / discharge cycles and see where we are at.

Thanks for the help.

#31

John,

Please let us know how your revived battery compares to the original capacity rating when your all done with the cycling.

Its pretty common for these batteries to provide 80% of rated capacity in the best of circumstances after about fifty cycles or so.

Michael

#32

First pass on balancing went well. 3 cells identical, one cell .01V down. I’m running a discharge now, then will balance again. My charger will not automatically repeat a charge/discharge cycle so maybe 3-4 is what it’s going to get - no way I’m doing it 50 times!

Those numbers at the bottom right of the charge screen are called “capacity” in the manual I have (which is for a different brand using the same chip), are they in Mah?

#33

John,

I’m very confident your charger can automatically perform at least three charge-discharge or discharge-charge cycles.

Yeah, I agree fifty cycles is lofty. I was suggesting what to expect after fifty cycles.

Yes, bottom right lower corner displays mAh capacity of either charge or discharge in play.

Michael

#34

All those poor little electrons. They get all grouped up to accomplish something, and then they just get discharged like so many sub atomic particles.

#35

Actually they go around and around in circles… ha ha

#36

Michael Glavin said:

John,

I’m very confident your charger can automatically perform at least three charge-discharge or discharge-charge cycles.

Yeah, I agree fifty cycles is lofty. I was suggesting what to expect after fifty cycles.

Yes, bottom right lower corner displays mAh capacity of either charge or discharge in play.

Michael

Thanks Michael. According the the manual I have it can only do that under the NiMh program. Under the LiIon program I have Charge, Balance Charge, Fast Charge, Storage and Discharge.

#37

Greg Elmassian said:

Actually they go around and around in circles… ha ha

Actually Greg, your close but no cigar me thinks. I’ll wager an AF Reserva #48 that the electrons migrate in circles around the outer circuit in opposite directions of the ions which simply shunt back and forth through the electrolyte, in either circumstance (ions or electrons) the direction or flow is dependent of charging or discharging.

(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-sealed.gif)Michael

#38

Daktah John said:

Michael Glavin said:

John,

I’m very confident your charger can automatically perform at least three charge-discharge or discharge-charge cycles.

Yeah, I agree fifty cycles is lofty. I was suggesting what to expect after fifty cycles.

Yes, bottom right lower corner displays mAh capacity of either charge or discharge in play.

Michael

Thanks Michael. According the the manual I have it can only do that under the NiMh program. Under the LiIon program I have Charge, Balance Charge, Fast Charge, Storage and Discharge.

John,

I took a look at a Tenergy T6 charger manual, looks like your right auto cycling regimens are only available for NiCad/NiMH cells. I don’t have one of the Tenergy chargers but evaluated Hitec’s rendition with a nearly identical chip many moons ago (I still use said Hitec charger today). To my delight I did discover that the Li-Ion charge regimen utilizies a factor of 4.10V to terminate charge… Its all good.

Michael

#39

(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-smile.gif)

My discharge cycle keeps timing out. Not wanting to heat the pack I’m discharging the 2200Mah pack at 1.0 Amp. My timer was set for 3:30 and it looks like that was about a half hour too short. I’ll increase it for next cycle. The charger says I got about 1400Mah out of the pack before the timer went out.

More cycles tonight.

#40

I may be missing something, but if you were discharging at 1 amp and you got 1.4 amp hours over 3.5 hours, how is the discharge rate 1 amp?

1 amp at 3.5 hours should be 3.5 amp hours…

Am I on a different planet? (don’t answer that Rooster!)

Greg