Lipo fire........cell imbalance? - Page 2 - RC Groups
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Feb 01, 2004, 02:11 AM
GRAVITY... Just Say NO!
ArcherAce's Avatar
Why were your running a 3s pack? That's over 11 volts. I'm thinking that is a bit much for the little GWS fans.
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Feb 01, 2004, 02:15 AM
BGR
BGR
Foam Junkie
Is it possible to put fuses on the batteries so that if the amp draw gets too great that it would blow the fuse? Maybe a slow blow fuse rated a bit higher than the full load amps.

I know that this would also result in a loss of control but its better than a meltdown.
Feb 01, 2004, 02:18 AM
Registered User
AussieParkflyer's Avatar
Thanks again mate for all your good advice.........

I don't think I'll ever know for SURE what happened this morning but if I replace the ESC with one that will definitely handle the current, and also make sure all my wiring harnesses and adaptors are well made then hopefully the A10 will rise from the ashes.


regards and happy flying guys

Aussieparkflyer
Feb 01, 2004, 02:20 AM
Registered User
AussieParkflyer's Avatar
Well ArcherAce I have tried to fly the A10 on 7.4 volt lithiums but it was underpowered.

I have had advice from several ezone members that the A-10 flies well on the 11.1 v packs, I even have a video here of a memebers A-10 flying great.........even so, if this were the case the motors would have burnt out rather than the batteries.

BTW my EDF55's are fitted with GWS 300H motors which supposedly will handle higher voltages than the standard 300's.
Feb 01, 2004, 02:25 AM
Nickel what?
Phreakish's Avatar
sounds like your Y harness may have had a prob and broke one of the wires to the pack thats still 'good' (although I dont think I'd fly that pack again, lol).
Feb 01, 2004, 02:30 AM
Registered User
AussieParkflyer's Avatar
Well Phreakish at the price I pay here in Australia for 3 cell lipolys ($85) I have to believe it is still ok.
I have charged it.........took about 250mah......seems ok so only time will tell.

I would love to be able to check individual cell voltages but I'm not keen to cut the pack open.
Feb 01, 2004, 03:42 AM
Fly it like you stole it..
Tram's Avatar
Can you not poke through the covering on the bottom of the pack and check each cell?
Feb 01, 2004, 04:30 AM
Registered User
The cells should be matched for best performance. If one cell developed a higher cell resistance then the other packs that are in parallel with it would have to make up the current. Also the lithium packs need to be kept flat. If they are bent in a crash then their internal resistance will increase. This problem is hard to detect if the cells are in parallel. The only way to check for it is to put a load on the cell and measure the voltage.
But I suspect that your problem was the poor wiring job on the battery conector. It does't pay to skimp on the battery wiring when the batteries cost $85.
Feb 01, 2004, 04:47 AM
Leave me alone!
Martin Hunter's Avatar

Re: Lipo fire..........cell imbalance?


Quote:
Originally posted by AussieParkflyer
Havent had any response to this query in batteries forum so thought I would re-post in the largest forum here.
I'm afraid that's not how it works. Cross-posting is a no-no. I see as many replies to the batteries query as this one, anyway. I'm going to close this down.

Martin
Feb 01, 2004, 09:39 AM
Registered User
Cell balance problems have been detected on brand new packs, so it does not necessarily require heavy use to cause imbalance:

https://www.rcgroups.com/forums/show...hreadid=184420

But imbalance problems usually show up during charging. The number of packs that have failed catastophically during flight is much smaller than those that have failed during charging or on the ground after being damaged in a crash.

When Kokam engineers analyzed a number of failed packs, they found that one of the leading causes was bad solder joints on the tabs. Here's a good message from Kokam's JJ Hong citing various causes they found for failed packs:

https://www.rcgroups.com/forums/show...86#post1435386

Many possibilities, but the ESC sounds like a leading candidate in your case. Even if it was the ESC this time, it is important to check cell balance periodically.
Feb 01, 2004, 11:53 AM
Sloping off....
leccyflyer's Avatar
I have merged the two separate threads started on this subject.

Brian
Feb 01, 2004, 02:08 PM
Rhinebeck CD-99,00,01,02
Tom Smith's Avatar

Aussie


If you are going to use 3 cell Lipo packs, you might want to use a speed controller that has a programmable LVC, low voltage cutoff, and set it to 9 volts for the 3 cell pack. Pulling too much juice out of those cells will kill them too.
Sorry to hear about the fire, but it could have been much worse. My buddies discharged pack shorted out on his way home, no crash or misuse either, and set his car on fire. He thinks it was faulty soldering in the pack, which he did himself.

Tom.
Last edited by Tom Smith; Feb 01, 2004 at 08:37 PM.
Feb 01, 2004, 07:39 PM
Space Coast USA
hoppy's Avatar
Quote:
Originally posted by Tram
Can you not poke through the covering on the bottom of the pack and check each cell?
As long as he doesn't "poke" thru the Aluminun foil lipo skin....ooops

hoppy
Feb 01, 2004, 09:00 PM
Registered User
You could put a fuse between the esc and the motors to remove the load but still keep the radio powered.