How to puff a lipo

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How to puff a lipo

Postby dogman dan » Fri Sep 17, 2010 2:48 pm

Simple, Hook up two 5ah packs paralell, and use a paralell adaptor that has one of the andersons pushed back inside. Then go run 8 ah out of the pack. :oops: I was concerned about this, so all my connectors were taped together to prevent an oops disconnect. But one bad anderson in the rig caused the same thing.

They really swell up when you try to discharge 8 ah from a 5 ah pack. :lol: Reads 0v now. Fortunately I only lost one 4s pack.
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Re: How to puff a lipo

Postby number1cruncher » Fri Sep 17, 2010 2:54 pm

Good CuggaMugga! You almost became the HotDogMan! Glad all is well.
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Re: How to puff a lipo

Postby philf » Fri Sep 17, 2010 3:23 pm

Wow. Impressive. And such an easy thing to have happen - yikes!
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Re: How to puff a lipo

Postby texaspyro » Fri Sep 17, 2010 3:31 pm

philf wrote:And such an easy thing to have happen - yikes!


And a easy thing to avoid and detect with a per-parallel-cell-group LVC monitor... any battery worth having on a bike is worth at least a minimal BMS.
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Re: How to puff a lipo

Postby number1cruncher » Fri Sep 17, 2010 3:42 pm

Dogman,

You may also want to reconsider paralleling the balance taps. I've had an anderson come apart on a parallel group, but the group maintained a decent voltage because the cells were also paralleled. Not sure it would hold up long under high discharge currents, but it would help for a while, as mine did.

texaspyro wrote:
philf wrote:And such an easy thing to have happen - yikes!


And a easy thing to avoid and detect with a per-parallel-cell-group LVC monitor... any battery worth having on a bike is worth at least a minimal BMS.
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Re: How to puff a lipo

Postby dogman dan » Fri Sep 17, 2010 5:09 pm

Good point. I've been toying with the idea of paralelling the balance taps, with 16g wire perhaps. then splice on the skinny wire. I got no respect at all for cheeze jst plugs. But that would be a chore. I dunno, you want to keep the pack flexible and easy to swap out stuff for racing, but you need to permanently paralell stuff. Or at least be sure nothing can come undone. Maybe I'll just hot glue the andersons into the housings after double checking that they are in and clicked. I just want the stuff to be able to swap out in seconds in case something goes bad minuites before a race.

Fortunately the fireworks would happen when I try to charge that puffy. But I'm not going to, it's in the dumpster.

The paralelled packs were sharing a lvc alarm. On the pack that wasn't connected. So no beeps from the pack happily sitting there not discharging. That can be fixed by moving the lvc to the other pack. I'm using a different method to paralell most of the pack, but used a seperate adaptor for the added 4s packs. Lack of proper planning, and eagerness to go burn some turns.
Last edited by dogman dan on Fri Sep 17, 2010 5:14 pm, edited 1 time in total.
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Re: How to puff a lipo

Postby tostino » Fri Sep 17, 2010 5:11 pm

I can imagine some crispy balance leads if that happened :lol:. Like you said though, it probably would have helped a lot. If it wasn't at a high C rate, you may have not even noticed.
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Re: How to puff a lipo

Postby dogman dan » Fri Sep 17, 2010 5:18 pm

Yeah. Can those things take 25 amps? I doubt it. That's why I was thinking, the only proper way to paralell the balance leads would be with thick wire, that could hack 10-20 amps for 15 min.

The more I think about it, taping the connectors is good enough to prevent accidental disconnect. And glueing the wire into the housing should prevent any backed out contacts. Sometimes a bent contact will click, but not really hold permanent. Gold bullets wouldn't back out of housings either.
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Re: How to puff a lipo

Postby knoxie » Fri Sep 17, 2010 7:01 pm

Lipo buzzer on each pack would have saved the Bacon here! I finally got them to stop blowing on me, each pack has one so even if the Andersons werent making it would beep, folks will pitch in about how its better to solder them in parallel and what not but like you I like the flexibility of running different voltages on the fly no problems here with buzzers and BM6 on each pack, pretty much fool proof and with the BM6 on each one its cell level on each pack, they stay well in balance so far.

Glad you only lost 1 pack and no fires
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Re: How to puff a lipo

Postby dogman dan » Fri Sep 17, 2010 7:18 pm

I'm going to redo my packs so the buzzer is on the pack that makes the final connection. The way I wired em, if one of them disconnects, the buzzer will be on the pack that is still providing power. Right now, it's the opposite, so the buzzer would be on the disconnected pack.

Are your buzzers permanently connected? that's the other issue, you're counting on some plug for that right? I'm currently connecting with wire nuts to the buzzers. If the buzzer plug is flakey the buzzer is useless too. Seems like they make a bit of heat, so I haven't hooked em up permanent.
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Re: How to puff a lipo

Postby texaspyro » Fri Sep 17, 2010 7:35 pm

Unfortunately the only proper way to interconnect packs in parallel is to have parallel connections at the cell level. Without those connections at the cell level, the paralleled packs cannot properly share the current. But balance leads just won't be able to handle the currents if something opens or cells get out of balance or go wonky. This is the major flaw in building bigger parallel packs out of LiPo modules and can lead to LiPo barbecues.

It would be nice if they sold those 6S1P packs as 1S6P's, etc. Then you could build up much more robust packs. And if one goes bad, you unhook it from the string and only lose 4V until you can replace it.
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Re: How to puff a lipo

Postby BIG BEAM » Fri Sep 17, 2010 8:30 pm

How come you guys don't use the 4mm connectors that come on the packs ?They even make bigger ones...5.5mm and I think 8mm.
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Re: How to puff a lipo

Postby chroot » Fri Sep 17, 2010 8:42 pm

Never mind, I see you mentioned run out super low below LVC. I got it clear picture. OUCH

That's why few of us mentioned rather have more than 10Ah so you have plenty ahead left the LVC line
to give you time to get home.
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Re: How to puff a lipo

Postby BIG BEAM » Fri Sep 17, 2010 8:47 pm

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Re: How to puff a lipo

Postby Hillhater » Sat Sep 18, 2010 12:26 am

FYI .. i produced a similar "puffy" when running 2 5s packs in series.
both were balance charged ( 20.5v) with cell logs fitted and i was monitoring every few min use, as they were new packs.
dispite the checks, i noticed the power drop off suddenly ( maybe 2 mins after a 3.6v check).
One pack was puffed and hot reading 1.9v/ cell !! :shock: ( note: cell log alarm is not loud enough ! ) but the other pack was still at 3.5v ?
I pulled the puffed pack out to let it cool..then peddled home.
Luckily, after a slow ballance charge (0.5A) all cells have come back up to 4.0v within 20mA of each other.

So lesson learned. ...
Get good LVC setting and cell monitoring alarms
consider thermal monitors & alarm for each pack also !
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Re: How to puff a lipo

Postby knoxie » Sat Sep 18, 2010 1:46 am

Hi Dog

I have my cell monitors in that blue box soldered to the 25 pin d plug, so its less likely that one can disconnect of course you would have to have 2 buzzers disconnect in 1 parallel block and that is highly unlikely you cant cover all the possibilities.

Those JST connectors wear over time I have noticed and some pins dont make a connection I see this as more of a problem, I think that if folks are going to parallel the packs at cell level and at the discharge leads they should consider soldering the balance wires and the discharge leads together I wouldnt rely on the JST connectors as you have the possibility that if 1 disconnects it will not show when you balance and that pack would never be balanced and would possibly go out of whack.

I agree if you dont want to change the pack voltages then paralleling the packs at charge and balance is the best idea but solder all connections.

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Re: How to puff a lipo

Postby curious » Sat Sep 18, 2010 1:49 am

Hillhater wrote:I pulled the puffed pack out to let it cool..then peddled home. Luckily, after a slow ballance charge (0.5A) all cells have come back up to 4.0v within 20mA of each other.

Don't use the puffed lipo pack even if it seems working OK. Major fire danger ! Really not worth the risk...
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Re: How to puff a lipo

Postby Hillhater » Sat Sep 18, 2010 4:17 am

curious wrote:
Hillhater wrote:I pulled the puffed pack out to let it cool..then peddled home. Luckily, after a slow ballance charge (0.5A) all cells have come back up to 4.0v within 20mA of each other.

Don't use the puffed lipo pack even if it seems working OK. Major fire danger ! Really not worth the risk...


Really !!
you know what worries me about that more than any actual fire etc ???..
..its the fact that this pack now appears perfectly normal, back to original size , 20.5v, all cells 4.1V balanced, etc etc..
no one other than me would know its history,
how many packs are sold after having testing "events" like this ??
.. is there no way of telling if you are using a potential incendiary pack ? :shock:
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Re: How to puff a lipo

Postby neptronix » Sat Sep 18, 2010 4:45 am

Wowsa, those are zippy flightmax, yeah? I'm surprised they didn't blow!

Well, i gained confidence in mine..

I am using EC3 connectors for mine. I bought a big 20 pack. It also helps that i'm running stock voltage on my controller, so i have a LVC.. nonetheless, i suppose it's easy for this to happen anyway :/
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Re: How to puff a lipo

Postby dogman dan » Sat Sep 18, 2010 5:18 am

Re hillhater. I bet you stop at 3.6 next time. I consider 3.75 time to stop, and have noticed that if you don't, you will hit 3.5 in about a mile or less. By 3.5v they are about to go over the cliff, and with only 5 ah, the cliff gets even steeper. From 3.5 to the ovedischarged would take no time at all.

2p 3s packs would be nice! Or even 3p 2s! Be perfect for the ebikes. Paralelling packs at 5s is not ideal. I did consider buying 2s packs. But then soooo many wires to connect. I'm trying to achieve the 10 ah pack with the minimum number of connectors.

I went with andersons because I like the flexibility of em, and don't need all 30 c discharge rate. They don't have the only plugs in one way feature that bullets usually have. I've only run across a bum one once or twice now, where the connector was pushed back. Usually the only issue is one coming unplugged. I've learned to crimp good, so I don't have to solder anything.

But this incident goes to show how closely you have to look at and also see everything on your bike. How many posts have you seen, " I unplugged everything and plugged it back in and it still doesn't work" Often a backed out contact on a phase or halls wire.
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Re: How to puff a lipo

Postby geetarboy » Sat Sep 18, 2010 12:42 pm

BIG BEAM wrote:How come you guys don't use the 4mm connectors that come on the packs ?They even make bigger ones...5.5mm and I think 8mm.
DON

Yeah, these are much better than andersons - my old e-bike kit battery connection was always coming loose.
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Re: How to puff a lipo

Postby geetarboy » Sat Sep 18, 2010 12:54 pm

Hillhater wrote:
curious wrote:
Hillhater wrote:I pulled the puffed pack out to let it cool..then peddled home. Luckily, after a slow ballance charge (0.5A) all cells have come back up to 4.0v within 20mA of each other.

Don't use the puffed lipo pack even if it seems working OK. Major fire danger ! Really not worth the risk...


Really !!
you know what worries me about that more than any actual fire etc ???..
..its the fact that this pack now appears perfectly normal, back to original size , 20.5v, all cells 4.1V balanced, etc etc..
no one other than me would know its history,
how many packs are sold after having testing "events" like this ??
.. is there no way of telling if you are using a potential incendiary pack ? :shock:

Hey Hillhater, I have a pair of 6s packs that have done the same thing. They were only "slightly puffed" compared to Dogman's picture, the lowest cell was @ 2.1 volts. I have 15 cycles on it since and it's working fine. Maybe we caught them just in time before irreversible damage was done? Mark
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Re: How to puff a lipo

Postby nicobie » Sat Sep 18, 2010 1:24 pm

I know most of you guys really like your Andersens, but I'm glad I went with Deans. Even though I use the cheap clones, I've NEVER had a problem with them getting hot. They are alot smaller and are impossible to reverse polarity when plugging in. Their only draw back is that on the male plug the prongs are exposed when disconnected. This isn't a problem if you pay attention and put the female on the power side and the male on the load side.

On my new build I'm going to try HK's new XT60 plugs. They are fully enclosed and handle 60a+ with out getting hot (so they say). They cost about $3 for 5 pair which is the equivalent of 10 Andersens.

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Re: How to puff a lipo

Postby amberwolf » Sat Sep 18, 2010 1:49 pm

FWIW, those balance leads wouldn't need to take much current, if any, under normal use. And if they did take more than they were supposed to, perhaps the smell would alert you that there was a problem, before they actually melted enough to short together and start a fire. ;)
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Re: How to puff a lipo

Postby texaspyro » Sat Sep 18, 2010 3:37 pm

Under normal "normal" use one would not need balance connectors, BMSes, etc at all. It's those pesky real-world "normal" conditions that cause all the irritating problems.
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