A123 battery back from the dead - what to watch for?

[grosbeak]

I left the 2500 mAh A123 battery in my current project on for several days. When I tried to charge it in LiFe mode I got a low voltage error (as expected). A little research showed me that I could charge it as a NiCd for several minutes to bring the voltage up, which I did. After ten minutes I tried the LiFe charge again. No low voltage warning, and the battery balance charged to 2488 mAh.

So it looks like I got my battery back. But is there anything in particular I should watch for?

[itizme]

Make a discharge and charge set for 3 times and if all good its ok.
Retest before first flights the same way to reconfirm but the first discharge will tell you everything on that day as either it was good or bad.
That's what experience shows me for a lifepo4 in a set of cans

[R Plante]

What's your plane worth compared to a new battery get a new one keep this one for bench work and set up I replace all flight packs every 2 years as insurance 10 or 12 packs each time my planes are worth more than a pack to me

[grosbeak]

From what I've read here and elsewhere it's worth cycling the pack to see how it responds. Unfortunately my charger (Hitec X1) does not have a cycling mode; I will have to run manual charge/discharge cycles which will take a little while.

With a fully charged pack I set it to discharge (1.0A, 4.0V). Unfortunately the 120 minute safety timer cut in with only 1700 mAh discharged. I charged it up again and set the timer to 180 minutes. It's running now - we shall see.

I will share the results when I have them.

[R Plante]

I had 2 batteries out of 4 in my pilot yak start taking less charge than the other 2 at the end of last season so all 4 were pulled and trashed ... 4 packs at 40 each or a new 40% plane that's a no brainer in my world. You have put a lot of time and effort into the details of your last build is it really worth risking it over a 40 dollar battery? doesn't seem to be in your nature to take a chance like that.

[grosbeak]

Here's what's happening.

Tried a discharge with the 180 minute timeout and the following settings.



When I came back to the charger this is what I found.





From the manual:



The newer version of the manual states:

If you plan to discharge your battery to reach safe storage levels we strongly
recommend that you use Storage Mode.

So after recharging the battery I tried that. Default settings:




Result:






Clearly the storage mode is not taking enough out of the battery to be considered a proper discharge, but the discharge mode encounters an error.

Does that low cell mean that the battery is toast*?

*This is academic; a new battery has already been ordered. But I would like to know.

[itizme]

I don't think anyone is willing to make a determination without being the hands on person.

If you discharge 3 hours at 1 amp your bat needs to be fully charged rated at minimum 3 amp or 3000mah
If you are going to discharge from storage charge that's a much lower capacity.

I'd suggest chucking it to the side for bench work and getting a new one before I'd advise further.
I would advise batteryuniversity.com and do some reading about bats, never hurt anybody that I know of

http://batteryuniversity.com/learn/

[grosbeak]

I don't think anyone is willing to make a determination without being the hands on person.

Maybe not here... but on other forums they have not been so shy!

If you discharge 3 hours at 1 amp your bat needs to be fully charged rated at minimum 3 amp or 3000mah
If you are going to discharge from storage charge that's a much lower capacity.

I'd suggest chucking it to the side for bench work and getting a new one before I'd advise further.

That is the plan.

I would advise batteryuniversity.com and do some reading about bats, never hurt anybody that I know of

http://batteryuniversity.com/learn/

Thanks for the tip - I'll check that out. I don't claim to know everything... not past the age of 18 anyway!

[grosbeak]

My replacement arrived.




A quick charge...






The old one has been demoted to bench duty.

[Grizak]

Best thing to do when you have a questionable A123 or LiFe pack is to charge/discharge each cell individually. Because the voltage (and discharge curve) of the pack is so flat - most chargers have a hard time balance charging these packs when the cells are really far out of balance. Because of this you will have a hard time discharging and charging a pack that is severally out of balance (it will also be hard for you to tell that a pack is severally out of balance)

You can easily charge each cell by making individual cell charge harnesses using JST extensions (you just cut the one wire for the second cell on each harness - so you have a right side cell harness and a left side cell harness). This way you can use the regular charge/discharge feature and focus on one cell at a time. Working with one cell at time takes the "balancing" variability out of trying to determine if you have a problem.