Espritmodel.com Telemetry Radio
Reply
Thread Tools
Old Aug 18, 2012, 01:31 PM
Registered User
snelan's Avatar
Joined Jul 2012
413 Posts
Discussion
Bringing LiPos Back From The Dead

Hi guys-

So I fly FPV, and about a month and a half ago, landed one of my planes in a very nice tree about 100 feet up. It just came down today, and, to cut to the chase, my LiPos were at about 0 volts (0-1 volts on two 3 cells).

Anyway, I have this pretty rough method I use to bring LiPos back, which is charging them as a NiCAD at 1 amp until they accept a charge from the LiPo charge mode. I use a Dynam Supermate DC6 for this. I know this is dangerous, they are kept in LiPo bunkers the rest of their life, and I sit by them as they are revived.

However, I was wondering if this process really revives them, or if it just seems like it does. I can get them to accept a full charge and discharge, but even still, it was pretty bad in this case. Usually the LiPos I do this to were at 5-6 volts, but these were at 0 to 1 volt.

I have two LiPos, a 1000 3s, which wasn't puffed at all, but was at about .5v, and a 5000 3s, which was severely puffed, same voltage. They both have retaken a charge, and have been balanced, but I am curious as to whether they can ever fly again in a plane I don't care much about (the plane that crashed and is now frankenstein with more glue). Do they still have the same, or close to the same discharge rate? Should I worry about the puffed one? I believe the reason the other didn't puff is because it was held tightly with tape, so there was no room for puffing. They were both Turnigy LiPos from HK.

Anyway, I am going to keep a close eye on these, will report back with further results. I made this thread so the battery experts can yell at me for this and help me to answer some of my questions.

If it matters, my restoration process is:
1 - Charge at 1a as NiCAD
2 - Charge to full (~12.5v) as LiPo when they accept charge
3 - Discharge with charger
4 - Balance charge to full
5 - Discharge with charger
6 - Balance charge
7 - Repeat discharge/balance until battery is balanced to an acceptable limit

Thanks!

~Sean

EDIT: Also, just realized I could use these to power my FPV ground station.
snelan is offline Find More Posts by snelan
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 18, 2012, 02:43 PM
characters welcome!
Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
26,210 Posts
http://www.rcgroups.com/forums/showthread.php?t=1074181

mw
Mark Wood is offline Find More Posts by Mark Wood
Reply With Quote
Old Aug 18, 2012, 02:55 PM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,565 Posts
Quote:
1 - Charge at 1a as NiCAD
That IMO is way to great of a charge rate to use for recovery. The rate needs to be low as in 1/10C or even less in the early stages.

In the end the Lipoly may recover but it has suffered real permanate damage if the cells spent hours below 3.5 per cell so do not expect much from it.
everydayflyer is offline Find More Posts by everydayflyer
Reply With Quote
Old Aug 18, 2012, 05:32 PM
Registered User
snelan's Avatar
Joined Jul 2012
413 Posts
I'm expecting nothing actually. Just because this battery is so far gone already (the 5000) I vented the cells by poking holes in them. No more swelling, but now the cells are down to around 3 volts total, so 1v each, before venting and after sitting in freezer I measured 3v per cell. I may have ruined the cells, didn't poke too far in, just the outer layer of sheathing. I used a black sealant and wrapped the cells super tight in electrical tape. I put a few more layers around the holes that I made.

I may have let oxygen get in and destroy them, we shall see. Charging as NiMH now, it seems to work better than charging as a NiCAD.
snelan is offline Find More Posts by snelan
Reply With Quote
Old Aug 18, 2012, 07:40 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
20,730 Posts
You are very lucky.
Others doing what you have done with charged cells ended up with a blowtorch in their hand.


Here's what can happen with charged cells.
http://www.rcgroups.com/forums/showp...&postcount=155
http://www.rcgroups.com/forums/showp...38&postcount=4
http://www.rcgroups.com/forums/showp...9&postcount=64

The question is how far poking in is too far. No matter, once the seal is ruptured and O2 gets into the pack, it is reported to be shot.
hoppy is offline Find More Posts by hoppy
Reply With Quote
Old Aug 18, 2012, 11:47 PM
Registered User
snelan's Avatar
Joined Jul 2012
413 Posts
Yep, after hours trying to force a charge into the 5000 after piercing the seals to un-puff it it vented. Lots of smoke, some flames. My other battery is taking a full charge 987MAH put into it, it's a 1000MAH, so not gonna experiment with that. The 5000 only took 2300MAH before my experiments started so I would of probably just threw it out anyway.

Ahh well, it was fun!

EDIT: Also, gotta use a toothpick in the future, used a razor blade and I believe it caused an internal short.
snelan is offline Find More Posts by snelan
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Help bring an OS .91 back from the dead? rc2xs Engines 14 Nov 22, 2008 06:36 PM
Question Should I bring back my King2 from the dead? chrise2 Micro Helis 6 Jun 15, 2008 05:06 PM
Discussion Bringing back dead lipos part II grampi Batteries and Chargers 9 Apr 15, 2007 08:31 PM
Discussion Bringing dead lipos back to life. ghostmechanic Batteries and Chargers 21 Jan 26, 2007 09:29 PM
Bringing a Moth back from the dead, 1 or 2 Q's I'm Rick James Slope 7 Nov 28, 2005 02:10 AM