RC Groups

RC Groups
    Xtreme Power Systems
        Discussion Capacity Testing XPS

#1 ezflyr Jan 29, 2013 02:38 PM

Capacity Testing XPS
 
Hi All,

I have a pair of 2S, 2300 mAH A123 packs I purchased from XPS about a year ago. At the time I fully charged them with a Thunder Power balancing charger. I'm about to use these packs now, so I'd like to capacity check them first. When I attempt this, I end up with a ridiculously low capacity of 75 mAH or something like that. When I recharge the packs, that is approximately the same amount being put back in. I assume I'm not discharging them properly, and probably ending prematurely. What is the per cell cutoff voltage that is appropriate to these A123 batteries?

Anything else I might be missing?

Thanks,

John

#2 E_ferret Jan 29, 2013 03:15 PM

Quote:

Originally Posted by ezflyr (Post 23970597)
Hi All,

I have a pair of 2S, 2300 mAH A123 packs I purchased from XPS about a year ago. At the time I fully charged them with a Thunder Power balancing charger. I'm about to use these packs now, so I'd like to capacity check them first. When I attempt this, I end up with a ridiculously low capacity of 75 mAH or something like that. When I recharge the packs, that is approximately the same amount being put back in. I assume I'm not discharging them properly, and probably ending prematurely. What is the per cell cutoff voltage that is appropriate to these A123 batteries?

Anything else I might be missing?

Thanks,

John

You can use your computer for more than communicating with Jim!:D
required information is only one click away;
http://www.a123systems.com/Collatera...ta%20Sheet.pdf

#3 crazy8s Jan 29, 2013 06:35 PM

Quote:

Originally Posted by ezflyr (Post 23970597)
Hi All,

I have a pair of 2S, 2300 mAH A123 packs I purchased from XPS about a year ago. At the time I fully charged them with a Thunder Power balancing charger. I'm about to use these packs now, so I'd like to capacity check them first. When I attempt this, I end up with a ridiculously low capacity of 75 mAH or something like that. When I recharge the packs, that is approximately the same amount being put back in. I assume I'm not discharging them properly, and probably ending prematurely. What is the per cell cutoff voltage that is appropriate to these A123 batteries?

Anything else I might be missing?

Thanks,

John

I apologize in advance if this sounds insulting (not meant to be) but you ARE using a charger that has a LiFE setting on it, right??

#4 ezflyr Jan 29, 2013 10:13 PM

Quote:

Originally Posted by crazy8s (Post 23972928)
I apologize in advance if this sounds insulting (not meant to be) but you ARE using a charger that has a LiFE setting on it, right??

Hi,

Yes, the Thunder Piwer TP-610C does have a LiFe setting! The default cell discharge voltage is 3.3V, so I was seeing virtually no capacity after a full charge. Once I saw the discharge curves, I realized I could set the cut-off to 2V, and now I'm measuring rated capacity!

Thanks!

John

#5 Doffen24 Jan 30, 2013 01:32 AM

Quote:

Originally Posted by ezflyr (Post 23975109)
Hi,

Yes, the Thunder Piwer TP-610C does have a LiFe setting! The default cell discharge voltage is 3.3V, so I was seeing virtually no capacity after a full charge. Once I saw the discharge curves, I realized I could set the cut-off to 2V, and now I'm measuring rated capacity!

Thanks!

John

Do not go as low as 2V. Minimum Voltage should be 2,5V. Almost no difference in capacity between 2,5 and 2,0 volts due to steep discharge curve. Your batteries will last longer though....
(said that, a couple of my A123 cells where discharge completely -due to forgot turning off-, and I got it back to ŽlifeŽ again after a couple of cycles ;) . They never seem to stop surprising me)

#6 JimDrew Jan 30, 2013 09:05 AM

3.3v is the normal operating voltage. A123 cells will retain their voltage for a very long time and then suddenly they will rapidly drop all of the way to zero. Cut-off at 2.5v and that will give you your capacity.

#7 ezflyr Jan 31, 2013 07:36 AM

Hi All,

Actually, I misspoke. The minimum cut-off voltage on the Thunder Power Charger I'm using in LiFe mode is 2.5V per cell. At that setting, I am getting rated capacity from my XPS A123 packs!

A special thanks to E_ferret for pointing out all the new-fangled things I can do with these computers :D!

John

#8 E_ferret Jan 31, 2013 03:26 PM

Quote:

Originally Posted by ezflyr (Post 23988834)
Hi All,

Actually, I misspoke. The minimum cut-off voltage on the Thunder Power Charger I'm using in LiFe mode is 2.5V per cell. At that setting, I am getting rated capacity from my XPS A123 packs!

A special thanks to E_ferret for pointing out all the new-fangled things I can do with these computers :D!

John

You are welcome! If you need further help, I cut my teeth (so to speak) on IBM 407s, so if you need help with point-to-point wiring, I'm the man.:)


All times are GMT -5. The time now is 05:07 PM.