A123 AMP20 cell diagnostics

[docnjoj]

Thats interesting. At one point I accidentally did something and the Thunder switched over to Lilo. It shut off at 3.9 volts on the A123 and sounded a warning. I then immediately put resistors on the high cells and brought them down to 3.6 After that the cells took much longer to balance and I had to use the resistor Battery Medics while I charged to get the cells in line. After about a week of rides (4-5 of 20 miles each) it is now balancing again. I don't know how it switched from LiFe to Lilo but it is back to regular even balancing. We will see next week if all is OK. All cells now are at 3.45 within 0.01 of each other. This was the only time I ever overcharged these A123 cells.
otherDoc

 

[dnmun]

they don't look balanced to me. what makes you think they are? have you ever measured capacity on any of these cells and can you tell how close they are in terms of capacity?

 

[arkmundi]

they don't look balanced to me. what makes you think they are? have you ever measured capacity on any of these cells and can you tell how close they are in terms of capacity?

Hopefully, with the Thunder 1220 properly setup and working, I can do a good discharge/charge test, as well as internal resistance test, so as to have more useful information on what I've got. So no, never had the equipment. And no, I'm not willing to pay-thru-the-nose for a more sophisticated setup. I'm way past budget on this little project of mine, monetarily, temporally and emotional/spiritually.

 

[999zip999]

Doc don't worry 3.9v or 4.0v wouldn't kill the cell as you took it down .It didn't sit there that long. You should be fine.

 

[999zip999]

Ark once you get the 1220 worked out all will come togethere. Couldn't Doc help as he is in love with his 1220. And he is close to being a programer by now.

 

[RayGo]

I'm especially happy with my Thunder T1220 charger since I got it used for $50. However, I just wanted to point out 2 issues I have with the unit. The T1220 has a discharge capability that I used to check the capacity of my A123 20Ah cells. However, the discharge rate was at 1 amp no matter what discharge rate I set. So my capacity test took almost 19 hours for just one cell which came in just under 19 AH. I'm just too lazy to test all 12 cells at this point.

arkmundi - Ask the vendor (hobbypartz.com) about that function's discharge rate if you get a chance.
999zip999 - You just missed a 10% discount sale on the T1220's $89.00 price at hobbypartz.com

Concerning the IR testing for the cells and the pack with the T1220, I would refer you to wb9k's post on July 20th on page 3 of this thread. The T1220's IR test values vary significantly during charging of the pack. I've seen a cell's IR go from 0.9 to 4.1 mO during the same charge cycle. I consider the IR values as a relative baseline for determining the health of the cells and pack and would not get to concerned about the actual IR values. The IR testing is indicating that I have 2 cells that consistently have higher values than the others that bears closer monitoring.

Anyway, I'd rather spend my time riding my e-bike. I just completed a 28+ mile ride this morning with my bicycle club and only used about 7 AH. I was pedaling more than usual today since I was testing out my new clipless pedal and shoe setup. Yes, I managed to fall twice. I've been told you need to fall 3 times before you get used to the clips.

 

[999zip999]

Yes not for a discharge test the charger will blow up. You have to listen to Dumun for the discharge test. But thru the charger good luck. Or please don't do it.

 

[major]

Hopefully, with the Thunder 1220 properly setup and working, I can do a good discharge/charge test, as well as internal resistance test, so as to have more useful information on what I've got.

Hi arkmundi,

I was following this discussion about your Thunder 1220. Did you finally get it working properly? Is it actually balancing the 20Ah 12S pack?

I bought a Thunder 1220 a few months ago and I have used it on some of the EnerDel 12S, 35Ah batteries. I also have tried it on a couple of 6S, 44Ah A123 batteries. I don't get any errors, but it requires an awful long time to balance. Like going through a full charge cycle and then restarting several times after that. I have the charge set to 5A. And the cell resistance readings are all over the place. BTW, I'm using a one kiloWatt RV supply which sits at 13.7V for the input to the charger. That seems to work great.

Any information or reference threads on this charger would be appreciated.

Thanks,

major

 

[arkmundi]

Sorry, no. Sent back to HobbyPartz for "Testing". Best!

 

[RayGo]

I usually just bulk charge at 3 to 6 amps. Then I follow up with a balance charge at 1 or 2 amps. This gives me a faster charge time over trying to balance charge at the higher amps. The T1220 seems good at not exceeding the set cell voltage limit.

I usually just bulk charge my A123 20AH cell pack. Then I use my Cell-Logs to check the cell voltages. The pack tends to stay in balance by itself with less than 100mv deviation. After 3 or 4 bulk charges only, I then run a bulk/balance charge with the above method. Cell voltage deviation averages about 20mv with this balance charge.

Yes, the IR values are all over the place. I've seen my 12s pack IR values range from 17 to over 50mO after charging. With balance charging, I can see that 2 of my cells consistently have IR values double that of the rest. I use these IR values as a baseline to monitor the health of the cell rather than worry about the actual values.

 

[cybercrash]

What about this charger:


http://www.youtube.com/watch?v=1GK6ojJw0m8

 

[docnjoj]

Just an update on the Thunder 1220. It has been flawless for the last eight months or so. Charges to 3.61 and very little deviation. Battery easily does 21 miles on about 11AH (efficient trike). It is my primary charger and the Hyperion sits.
otherDoc