Odd battery behavior, cell mismatch

[Fairbarnacle]

I am experiencing some odd battery behavior from a relatively new 2S 5000mAh Revolectrix battery that I purchase from OSE 9/20/21. I am not new to lipo battery use and assume this battery should not be trusted but am curious how this battery is failing. The battery has less than a dozen discharges on it (never lower than ~3.6 volts/cell) but I have to admit that I left a full charge on it for a week once. If full, I typically discharge my batteries down to 3.7/cell with a computerized battery analyzer (http://www.westmountainradio.com/pro...oducts_id=cba4) then storage charge with my ToolkitRC M4Q 50W 5A 1-4S Quad Channel AC/DC Smart Charger. I noticed cell #2 decrease to below 3 volts then up to 3.8 when cell #1 dropped to below 3 volts. My small cell checker device shows ~3.8 volts/cell when it is not charge/discharging. I tried to fully charge it to see what the IR showed and it looked OK until I approached ~4.1 volts/cell then the cells started behaving the same. About to discharge it to 0 volts and dispose of it.

Video showing unstable cell voltage during charge:

https://photos.app.goo.gl/2kJLy7fv3zynCaNC6

[fweasel]

Yep, I wouldn't trust that either. However, because it's newer (technically from the future if you bought it in September of 2021), could it just be a bad balance cable connection? When the individual cell voltage drops (a reading off the balance plug) what does the total voltage look like (read from the main power leads)?

[Panther6834]

Recently, I had the same thing happen with a couple of my packs...a 6S from Revo, and a 4S from Dinogy...granted, neither has been used for over 6 months. With both of the packs mentioned, all cells, except one, were still within "storage level" range...but one cell on each was well below (on the 6S Revo, it was at 2.7V...on the 4S Dinogy, it was at 1.9V).

In order to 'resurrect' both packs, I followed the same process I've done before (and one that RC Review covered, step-by-step, in one of their YouTube videos...you might want to check it out), which involves charging the pack with the "battery type" set to NiMH, at (closer to) the lowest Amperage seeing possible, until all cells are above 3.2V. That means disconnecting the pack from the charger, and checking using a separate Voltage checker, approx every 5 minutes. Once ALL cells are above 3.2V, then plug the pack back into the charger, and charge as LiPo. In doing so, still charge (this first time) at a somewhat-low Amperage...and, if your charger has multiple 'balance charging' settings (as my iCharger 406 Duo does), set it to "slow balance".

After following the above steps, keep an eye on any packs charged this way for at least the next two charging/usage cycles. In doing so, always put them back to "storage level", and then wait 2-3 weeks before attempting to charge them again. When doing so, chick to see if any individual cells self-discharged lower than the other cells (by 'lower', I don't a few 10ths lower...I mean "considerably below 3.2V lower"). If the same cell goes considerably lower a second time, them, to I agree on the "dispose" mentioned in the previous reply. If a different cell goes considerably lower to then something else is probably going on, but the pack should be safe enough to 'resurrect' a second time. However, of the same pack needs to be 'resurrected' a third time (same, or different, cell) then there's something SERIOUSLY wrong with the pack, and I'd contact the manufacturer IMMEDIATELY, as who knows how many other packs manufactured during that same period of time could be having the same problem.


~ More peace, love, and kindness would make the world a much better place

[jkflow]

As per @fweasel, check the main voltage and see if this is a true issue. I suspect just dirty connections on the balance plug.
Lipos are not capable of doing what you are observing.
I have similar things happening, and it's always a dirty connection.

[Norwest]

charge connection

Now, ur definition of dirty connection of balance plug! Thank you! I would like to know. The tiny wires attached to metal that fit over pins or broken wires or a pin which has receded or a pin that is bent?

[jkflow]

Oxidation, anything that will prevent good contact between your meter and the balance plug itself. Connect your lipo checker and see if the reading changes by slightly moving each individual wire. You will see it change.
Use some contact cleaner or a small needle, just make sure you do not accidentally short out to the neighboring point.

[T.S.Davis]

Balance tap are my greatest complaint with most LiPo. $100 battery has a tap that's worth about a nickel. They corrode easily or break the prongs off inside the plastic. Ugh. The taps on my HRB packs are much better but still not great. At least they have a body you can grab on to.

Sometimes your actual balance board can get funky from the charger itself. I struggled with that at a race thinking I was losing a cell. Pack voltage was right but wouldn't balance of course.

[NativePaul]

I am experiencing some odd battery behavior from a relatively new 2S 5000mAh Revolectrix battery that I purchase from OSE 9/20/21.

My guess it that it was overloaded and a cell died when your flux capacitor pulled 1.21GW from it.

I suggest giving your LiPo a week long salt water bath, then replacing it with a Mr Fusion reactor for reliability.

[Panther6834]

My guess it that it was overloaded and a cell died when your flux capacitor pulled 1.21GW from it.

I suggest giving your LiPo a week long salt water bath, then replacing it with a Mr Fusion reactor for reliability.

But that would only be if he exceeded 88mph.


~ More peace, love, and kindness would make the world a much better place

[plinse]

Oxidation, anything that will prevent good contact between your meter and the balance plug itself. Connect your lipo checker and see if the reading changes by slightly moving each individual wire. You will see it change.
Use some contact cleaner or a small needle, just make sure you do not accidentally short out to the neighboring point.

Thin wires soldered to something stiff can also break next to the soldering connection.
Like @fweasel wrote: Check the total voltage vs. the ballancer reading. Move both ends of all ballancer wires, slightly pull on them... and check for this influencing the measurement.

This behavior has to be understood, otherwise this LiPo is a risk I would not keep in my house. It is just not worth it.
I neither store or charge my LiPo in the house anyway. That is something I do outdoors.

Regards, Eike

[plinse]

...
After following the above steps, keep an eye on any packs charged this way for at least the next two charging/usage cycles. In doing so, always put them back to "storage level", and then wait 2-3 weeks before attempting to charge them again. When doing so, chick to see if any individual cells self-discharged lower than the other cells (by 'lower', I don't a few 10ths lower...I mean "considerably below 3.2V lower"). ...

Careful, LiPo don't care daytime, they can also burn at night
The maximum win is using a questionable LiPo a couple of times more. The maximum loss is the house and the people inside if the LiPo should catch fire for some reason.

I definitely do watch the 10ths in self discharge. The amount is one thing but that is also a function over time. The balance should definitely be kept.

In about any technical equipment batterie-management is automatically taken care of by your Laptop, ...
In RC is is the most faulty instance taking care of the batteries - the user

People needing too many tricks on their batteries often experience "thermal runaways" of their LiPo some time.

I only run boats/planes where I would be willing to throw the LiPo away if something should go worse than expected.

Regards, Eike

[NativePaul]

But that would only be if he exceeded 88mph.

Self evidently, he must have hit 88mph to have come back from the future.

Great scotts! That is some good speed from a little cat.

[Fairbarnacle]

Thanks everyone. I cannot reproduce the issue on anything other than this newer charger that I have. I put a brand new balance plug on it and it does the same thing with this charger. It's strange that it is just this battery and none of the other 5 that I bought at the same time do this. It could very well be a bad connection balance wire connection at the cell and not the plug. Curious if I can replicate the problem on a different charger. I have the ISDT battery checker and am really liking it. It will balance the cells better than most chargers that I have used (https://www.offshoreelectrics.com/pr...od=ker-ISBG-8S)

I'm sending the ToolKitRC charger back (bought from RaceDayQuads) for a refund since the charger also has some other quirks that I found this weekend.

Can anyone suggest a solid 4 channel AC/DC 1-8S charger with internal resistance reading? I was using Venom and had issues with them as well.

[jkflow]

Limited choice with 8S.
I'd get an ISDT, for 6S I have a HOTA myself, and its great.
No idea what cells you are running but get a minimum of 150W per channel on AC, not a 200W (combined) or some other nonsense like that unless you only have small cells to charge.


Stay away from anything with ancient LCD displays, it's 15+ year old technology in a new make-up. They are literally all the same, other than the housing.

Good recommendations are here, it's an active forum but an older thread. Go towards the last pages, linking to pg 30 but feel free to go to the end.
https://www.arrmaforum.com/threads/r...r.1079/page-30

[Fairbarnacle]

The toolkitRC charger released it's magic smoke at the races Saturday. Seems like I am not the only one with issues using this charger. I ordered the HOTA D6 Pro 325W to replace it.