New HK Turnigy LiPo Pack Problem: Missing a Cell?

[GMUseless]

I've got a problem with a Turnigy 6s 3000mah pack I ordered from Hobby King's US warehouse. I ordered 16 packs..and just finished checking all the cell voltages with a CellLog.

One pack reported an error when I hooked up the CellLog. I checked the main pack voltage with a DVM and it read 19.1 volts. I probed the balance tab...and it looked like one cell was just missing. Nothing in the first position (between the black and red balance wires.) The remaining 5 cells read around 3.8 volts.

I plugged the pack into the CellLog again, this time offsetting one position. The CellLog came to life and provided the readings. The results are below:



Any ideas? Is this perhaps just a 5 cell pack in the wrong package? Could the missing cell be in there an not connected? If so, wouldn't that be asking for self dishcarge problems at some point?

 

[GMUseless]

Just weighed the pack: 490 gram. Just like all of the other 6s packs. I'm guessing the cell is in there...and either completely shot or not connected.

 

[neptronix]

That's weird. That cell could have a voltage of 0.0, or just not be connected in series at all.

Talked to hobbyking about warranty yet?

 

[dogman dan]

Most likely just a crappy jst, or it's disconnected on the inside. More common, one pack of a good size order comes defective somehow, puffed, or one cell or more reading below 2v.

Lot easier to send back a bad pack to the USA warehouse so I like to buy from there if possible.

Welcome to HK, cheap, but figure on at least 10% of lipo to have some kind of issue. For bikes, we buy such big piles of the stuff we always get one.

 

[GMUseless]

Yeah...I'll try the warranty route. I thought about the JST being wired wrong...but then the main pack voltage adds up like it's a 5S. And I figured if one cell had become disconnected...wouldn't that likely kill the main output since the whole thing is in series?

Oh well. In Hobby King's Lithium warranty policy...they say all cells must be returned to the Hong Kong office. I hope that's not the case for stuff purchased from the US warehouse.

 

[dogman dan]

What I mean is the balance wire to the jst plug is disconnected. So you can't read any voltage on that prong of the plug. Inside the pack, the cells themselves are still solidly soldered to the pcb board that connects the tabs in series.

Chances are, it's a super easy fix, but cutting off the wrapper to fix it likely voids the warrantee.

Here's what you can do though. That little black wire that is disconnected is soldered to the same place as the main - wire. You should be able to check that cells voltage by touching a voltmeter to the main - wire and the wire next to the broken black wire on the jst plug, the brown one.

If it shows 3.8v or thereabouts, screw the waranty and open it up to fix it. Just open the top of the shrink wrap, and peel off the first inch. I bet it's just a jerked loose wire.

 

[DAND214]

If the main connector read 19v then the cell is dead. The missing wire won't help to bring the voltage up.

Send it back or cut it open to see which cell is dead.

Either way it's a 5 cell pack now.

If I had time I'd send it back before I would cut it open.

Dan

 

[Ykick]

As I recall you bought a couple extras? And now you're checking it out carefully - this is why I mentioned in your build thread you have the right mind for doing Lipo.

IMO - 'looks like you probably have a shorted cell. Balance wires are often funky and intermittent for me but if the total brick voltage is 3.8 x 5 you must have a shorted cell. 'could be a dangerous situation...

Try the warranty route before anything and worst case, learn to do a little "brick" surgery. Ypedal has great video on that and you can cull spare cells and/or repurpose for other applications. Lighting, car starting, etc.

 

[dogman dan]

Duhh, yeah. 3.8v x 6 isn't 19v Bet that last cell is dead. I'm too used to thinking in 5s where 19v would be about right for a new uncharged pack. Interesting that it reads 0v. Rather than .5, 1.5 or something.

 

[GMUseless]

Thanks Ykick. I thought the same. And indeed I had ordered two extra packs. When I made the decision to use LiPo...I decided that until I amass some experience with them...that I'd not try to run anything out of the ordinary: puffy's, cutting out dead cells, etc. I'll get a handle on the normal conditions before tackling the abnormal ones.

I had figured I'd probably get some type of issue ordering 16 packs from HK...but I thought it would a puffy cell or suspsicously low cell voltage...not a missing persons case.

It's almost like it's a 5s pack with the wrong JST and label. Expect for the fact that it weighs the same as the 6s packs. So I'm guessing it's some type of factory error. I'll contact Hobby King and see if I can send it back. If not, Dogman...weren't you looking for race LiPo donations? Maybe I've got 83% of a 6S pack for you...

 

[dogman dan]

Not looking for donations at this point. If I do race again, it will likely be in the old fart going slow class. I found my level at 40 mph. When I took it up a notch to 47 mph, I just started crashing and melting motors.

I won't need a lot of battery to ride just for the fun of it.