Acceptable lipo condition from Hobbyking

nutnspecial

nutnspecial

10 MW
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Hobby king is pretty much the 'go-to' for lipo, I found several old threads each miles long but know people have been constantly buying them, myself included. Since 2015 I've bought 10x 4s, 6s, 8s, 5800mah turnigys, of which only two (the 'odd' 8s) came in poorly balanced and puffed. I've also bought a few 16000ah multistars which also came in good. Never any noticible puff or imbalance past .02v in any pack besides the two oddball 8s, which I sent back. Dependability has been great for the ones I accepted.

So what is good, acceptable? In my experience, that's imbalance and/or puff, right out of the box. Although poorly matched cells will show in a few cycles, I'd like to focus on what to look for upon initial receipt.

I've just bought my first zippys - 8x 6s 5000mah 25c. They just arrived.
6x have among the pack cells of 3.76-3.77v
2x packs are at 3.74-3.75v

While that's perfectly acceptable, here's the issue. The 6x group have a noticible 'squish' when squeezing with your fingers. The other two are rock-hard, just like all but two I've bought before. While it's not a huge 'puff', it's there and can be seen, heard, and felt.

What do you do? Do you accept this sort of thing?

I'm expecting possibly noticably shorter lifespan from the slightly puffed packs, since whatever cells are puffed will have a tendancy to imbalance, most importantly to me there may be a increased risk of hazard.

Thanks for any input on this.
 
I wouldn't accept anything ohter than flat squared cells that are balanced and at about mid-charge level.

Also note that balance when unloaded means little; it's balance *under a load sufficient to match intended use* that will reveal Ri problems.

Any puffing means there could be gas bubbles between layers, meaning higher Ri, potential fire hazards, etc.

Any kind of physical damage or deformity to the cells affects their internal arrangments, and could also be the same as the above, with the additional risk of internal shorts between layers, which might not even show up until the cells warm up, cool down, or change shape for some other reason (stuffing them in a battery box, etc). Can be fires waiting to happen.

Any kind of imbalance could mean a cell with internal shorts that is leaking charge between layers, which could get worse, including a direct short that could lead to a fire, even when not in use (like John in CR's hardcase pack tabletop fire some years back).

Since you can't know till it happens, then even though the risk is probably very small, I wouldn't accept anything that has imperfections like those.


I've not a huge amount of direct experience but I have a number of RC LIPo packs from various members, some with almost zero (or actually zero) use on them that were "imperfect" in various ways upon arrival, and all of them operate imperfectly, too. Some of them worked well enough for a long while, some of them were unusable without disassembling and swapping out cells, which risks further damage to the other cells due to phsyical handling, bending, etc.

I've also read the many reports of problems and no-problems here on ES and some elsewhere, and see the correlation between the damaged packs and the reported problems.

If you have the time (lots and lots of it :() you can look up all the RC LiPo threads and posts and see the same things. But the above is the basic summary of them.
 
Thankyou. I was curious of other recent transactions and what is generally accepted/returned. Someone that's been around and taken part or even just read alot of past threads can offer an even more solid and balanced opinion.

Even my 2yo beaten up turnigy's don't have the same squishy light puffing, and they're on their way out with imbalance and self-discharge. I'm highly skeptical of these zippys but am not sure if it's common for them or what . . . Probably not.
 
Not current, from several years back, so I cant' remember for sure, but I think the Zippy stuff I got was iffy from the get-go when the original purchaser got it, but HK wouldn't take it back, so I ended up with it since it couldn't be relied upon. It could've been something else, but I recall that name involved with it somewhere.
 
its understandable to be dissatisfied with the "feel" or shape of some cells/packs, but unless you can identify a quantifiable defect, you may have a hard time convincing the supplier that it is unacceptable.
HK can be pretty good replacing obvious defective packs, poor balance, low voltage cells, damage, puffed cells, etc...but one you get to things like "feel" and appearance, then be ready for some questions, and even their insistence for return of the product for replacement.
..Just saying... 8)
.. of course, others have suggested ways of ensuring a "no argument" defect is reported. ! :wink:
 
like i say in my battery tutorial for series charging.. a cycle graph will tell you more about a battery than anything else. Do you have a nicer RC charger that can plot out a charge/discharge graph for you?
 
Several months ago I bought some Zippy's , then forgot about them since charging a Li-Ion pack was so easy. At least they all stayed at the storage charge of around 3.7 per cell.

Then when I went to charge them , one of them looked and still does, look a little puffy, But when I put it on the charger, it balances better than all the others . ? . ( I have now done 2 charge and 2 rides/ discharge to around 3.7 on 8 packs so far )
The slightly puffy looking pack is charging within .01 to .02 per cell when looking at the charger several times while charging .

Two of the Flat packs have a bad cell, although the 6s pack came in at an average of around 3.7 volts x 6 ( apx 22.2 v )
When I went to charge those two packs, one cell on each pack would not come up. .2 to even .3 difference.

So how do you know by just looking at the wrapper ? as two of the best looking packs of mine had one bad cell each .
and the one that looks a little puffy , has cells that charge at the same rate. ?
 
I have an i-106b that would work I think, just never tried it before.
Imo, isn't mapping all packs pretty similar to just putting them into real-world cycle, even if you run 2p? Perhaps each method has it's own benefits and drawbacks?

Eitherway, I was hesitant to do any kind of cycling when I already considered anything but rock-hard and balanced to be unacceptable.
I suppose some further evaluation is in order, as (afaik) it shouldn't risk anything against HK's hassle free returns, and I would prefer to keep them and be comfortable with their reliablity.
 
I got out the iCharger and DL its PDF and Logview.

Started with simple IR which I've never done. The two solid packs measure 30 and 32, the six squishy packs measure consistently >50 with slightly wider spread among the cells. I saw something like 4-6mohm vs 7-10mohm between the cells in the hard and squishy ones. Does that mean much?


I put 2s2p to bulk charge. I'm assuming It would be quickest to get bulk charged full then opt whether or not to graph the slow monotonous pack discharge and charge on the icharger.

edit//btw I tested the old beat turnigys. The 6s packs still behaving properly are measuring ~30mohm total, the bad ones have cells that are up over 40mohm per cell.
 
An update, with all cells @ ~4.17v

cell mohm range/ pack total mohm
. . . .3-8 . . . . 29
. . . .3-6 . . . . 26
. . . .3-5 . . . . 25
. . . .1-6 . . . . 22
. . . .2-5 . . . . 21
. . . .2-5 . . . . 21
. . .1-4 . . . . 16
. . .1-4 . . . . 12

I gave up on charge/discharge graphs for now, due to issue with usb cable or com port.
I'm thinking these readings aren't ridiculous? Though the solid packs are noticibly tighter and lower IR.

BTW, I just jumbled up all 8 packs, and gauged puffiness by sense. I picked the worst two out and rechecked. The are the 29mohm and 26mohm packs. Cell spread measures about 4mohm, which is very close to the best packs. Every cell just has higher resistance. Thoughts?
 
Internal resistance has a curve in it just like voltage. If the packs are at various states of charge, that explains part of the difference.

Do keep one thing in mind though.. the IR readings no the iCharger are not super accurate.. it is good with voltage and amperage.. but IR is kind of a wash.

Zippys are not known to be the best.. i've had the highest dud rate with them and i've ordered something like 40 RC Lipo packs so far from turnigy and zippy over the course of many years.
 
You are confirming my suspicions. I measured all of them at the 3.75-3.77v they came in at, then measured again at 4.17-4.18v. The two best packs and two worst packs tested accordingly each time. All in, they don't seem too bad. They now are back up to almost 500$ total, and I got these for about 260$, so it kinda is what it is. Along as they dont get weird (and dangerous) under normal usage.

I temporarilly put them together for drawdown, and will see how well they maintain balance at the 8-10c level discharge I've been planning. Thanks for the input so far guys, add in anything you find pertinent, thanks.
 
IR is highest near what we'd call the LVC and HVC, It's lowest in the middle of the charge.
It is what causes a cell to leap or dive more intensely around 0%-10% SOC and 90-100% SOC.

So unless your packs are perfectly well balanced, then comparing IR is not gonna be totally accurate.

By the way, this is what an A+ grade pack looks like on a cycle graph. Before the first cell hits 3.0v, our cells are hitting 3.0v at nearly the same time. This means the cells have very close to the same AH in them, and if we cut off as low as 3.5v nominal, we've got all kinds of fluff room to ride this pack without a BMS.

24_dischargingmechanics.gif


What you don't want to see is something like this.

zippydud.gif


^-- one cell is missing capacity

And Definetely not like this.. :lol:

leadershobby_sag2.gif


^-- IR of cells is all over the place. This 'new lipo pack' turned out to be made of recycled cells of various vintages. Even the pitiful 0.1C load placed on the pack produced wild voltages due to the massive difference in IR between the cells. China selling you back your trash..
 
I ended up strapping them all to the bike for some real-world testing. At this point I wouldn't expect to send back. I do plan to do some graphing when I get the ports straightened out. I don't think it liked the charger on port 8, or it didn't like the usb extension.

Anway, I'll have to carefully try to log what's happening on the bottom end, but I'm hitting them with 8c discharge- So far, down to 3.9v resting (confirmed), and it looks like they're sagging to about 3.75v w/82a from there.
///Further 'testing'. They're sitting at 3.81- 3.82 beautifully and have confirmed via alarm to sag to 3.5v under full load. *Jay thinks to himself : "I wonder how low I can safely sag them?" I guess I'll set the lvc for 3.5v and see how well they maintain balance over the next few cycles. Assumedly if they maintain balance the cells aren't going too crazy at the bottom.

24s is def fun though. It was ridiculous till I put the 13lb pack back on the front lol. I can re-gear back down <40mph in speed and the motor will like the higher balance of volts over amps. Batteries too.


I'm curious, what were the battery brandings in the last 2 of 3 test graphs? .1c discharge for 50sec is ridiculous for that last result- reallllly bad. What was the draw rate for the other two in amps?
 
That was a 10AH "10C" leadershobby transmetic battery pack doing the sagging on 1A.
The others were 5AH 20C turnigy on a 2.5A discharge.
 
I'd expect a 2.5ah load to last closer to 2hrs on a 5ah battery! I mean, I can understand reduced capacity if you're running 50a due to sag, but the first one only lasts 30min!? That actually makes the 2nd one look better w/ 50min of capacity before any cell effectively hits the cliff.

And how does that effectively transfer over when you're running realworld amperage of 5c /25a? They must sag horribly? All I know is I look for when the cells sag to the 'cliff', and limit draws there. So as a group they won't sag past that, and can't draw down past that. Always check balance, and if cells start to stray raise the lvc and/or drop the current draw. If they're matched IR and there's a buffer before the cliff (3.5-3.6v cutoff), it seems the batteries stay pretty happy?

Provided mine continue to perform properly, I'm pretty happy with 8c/80a draw from the 25c/10a battery, from 4.15v to 3.8v in 24s, and then hard limited draw down to a lvc around 3.5v or 3.6v. That's pretty much widely expected with these when you're running 1/4 to 1/3 of their rating, right? I mean, it'd be great to set the lvc down at 3v for more capacity, but especially at high draw it would end up wrecking any non-bms battery.
 
That's why people keep saying that just about none of these vendor ratings of multiple-C capability are "real", because if it sags that much, and/or creates taht much heat, and it doesn't get the full capacity out at those ratings, it isn't really capable of running at those currents.

Sure, you can do it for a moment here and there...but not continuously, which is what those ratings are usually said to be. :/

Unfortunately it's become "industry practice" for that kind of stuff to make up the best possible marketing lies so people will buy it, as most of them will never test it, and becuase it's been going on so long they no longer expect stuff to last very long....

Any vendor that *doesn't* lie about their packs' capabilities to make them look as good or better than everyone else, and instead only posted the *real* capabilities, wouldn't sell much and would just go out of business.
 
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