Notices
E-Flight Power Sources Ask questions or read about power sources as they specifically relate to e-flight including Lithium-ion, Li-Poly, Nimh and Nicad battery packs.

Discharged Li-Po

Old 05-21-2005, 05:57 PM
  #1  
Gullwing72
Senior Member
Thread Starter
 
Join Date: Mar 2005
Location: Dickinson, TX
Posts: 489
Likes: 0
Received 0 Likes on 0 Posts
Default Discharged Li-Po

I bought a 11.1v 4200mah Thunder Power battery with only 10 cycles on it from a hobby shop buddy a couple of weeks ago. Knowing that this guy knows his stuff when it comes to electric flight. When he said he would take $50 for it I jumped at it(he was having money problems and was selling most of his personal stock). First question: It has been setting in a drawer for I know for 2 weeks and don't know how long before then. Well it has discharged below the limit. Has it setting there done that? And question #2 can I revive it somehow? Thanks for any help...
Old 05-23-2005, 07:55 AM
  #2  
Matt Kirsch
My Feedback: (21)
 
Matt Kirsch's Avatar
 
Join Date: Jul 2002
Location: Spencerport, NY
Posts: 7,350
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Discharged Li-Po

Do you know what the voltage was BEFORE you put it in the drawer? LiPolys normally discharge veeeery slowly just sitting around. Two weeks, you shouldn't even be able to tell the difference in voltage...

If it dropped from a full charge down below the limit in two weeks, something is seriously wrong with the pack. It's a judgement call on your part, but I would ask for a different pack or my money back...

Now if your friend just ran it down to the limit, and left it sit discharged for a few months, that's different. What voltage is it at right now?

Bringing a pack back up needs to be done CAREFULLY. With a 3S LiPoly pack, the best way to go is to connect it to the transmitter side of a transmitter/receiver wall wart charger, then watch it with a voltmeter until it comes up above 9.0 Volts.
Old 05-23-2005, 06:35 PM
  #3  
Gullwing72
Senior Member
Thread Starter
 
Join Date: Mar 2005
Location: Dickinson, TX
Posts: 489
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Discharged Li-Po

I don't know what the voltage was before. I think he just ran it down. The pack looks to be in very good shape physically (not swollen or dinged up) The pack is at 5.21 volts now. I have a charger that will charge ni bats and lipoly down to .10, will that work as well? It would be easier than trying to connect it to the tx/rx charger. If not I will find a way to connect it to the wall charger... Let me know what you think Matt.....Thanks
Old 05-23-2005, 09:14 PM
  #4  
Matt Kirsch
My Feedback: (21)
 
Matt Kirsch's Avatar
 
Join Date: Jul 2002
Location: Spencerport, NY
Posts: 7,350
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Discharged Li-Po

5.21 Volts? There's not much hope of reviving that pack. Once you get below 7.5 Volts on a 3S pack, the writing is pretty much on the wall. I would also suspect that the cells in the pack are now horrendously out of balance, if one cell isn't dead outright. Trying to charge the pack, even slowly with a wall wart, is potentially dangerous at this point.
Old 05-23-2005, 09:33 PM
  #5  
Gullwing72
Senior Member
Thread Starter
 
Join Date: Mar 2005
Location: Dickinson, TX
Posts: 489
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Discharged Li-Po

Alright Matt, thank you for your help. My hobby shop bubby and I are going to have a talk tomorrow. I guess I learned that same old lesson.....If is sounds to good to be true than it is.......Thanks agian..............CDP
Old 05-23-2005, 11:58 PM
  #6  
supi7
Member
My Feedback: (2)
 
supi7's Avatar
 
Join Date: Feb 2004
Location: Chicago, IL
Posts: 74
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Discharged Li-Po

7.5V per 3 cell pack is no way safely rechargable. a 3 cell pack should not be dropped below 8.25V and even at this point most auto chargers will not pick it up.


I reccomend that you take it back. This pack is too far gone to risk recovery.


Best Wishes,

Dan
TrueRC

Old 05-24-2005, 05:37 AM
  #7  
Matt Kirsch
My Feedback: (21)
 
Matt Kirsch's Avatar
 
Join Date: Jul 2002
Location: Spencerport, NY
Posts: 7,350
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Discharged Li-Po

Hmm, original "conventional wisdom" on LiPoly packs was a 2.5 Volt per cell cutoff. That eventually became the "drop dead" point, and that's not to say that the pack would recover with 100% of its capacity and capability after being drawn down that far.

I agree, most automatic chargers won't even touch packs that are below 9.0 Volts, let alone 8.25 Volts.
Old 05-24-2005, 05:38 PM
  #8  
Gullwing72
Senior Member
Thread Starter
 
Join Date: Mar 2005
Location: Dickinson, TX
Posts: 489
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Discharged Li-Po

Hobby shop buddy was not there today.(out sick) I will catch him. I am thinking of cutting the shrink wrap off and seeing if I can get one or two cells salvaged out of it, that is if he tells me to kiss off. Don't want it to be a total loss.....

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.