leaderhobby LiPo packs? Has anyone experience with?

[cor]

Hi Neptronix,
I am *within* the 45 day period, so I hope to recover some of my money.
The one pack with the bad cell, I split in 2 (between the 2nd and 3rd cell)
and it was quite difficult to get the cells apart without damage or bending.
But I did not see the dreaded Tekocell printing. In fact, there was no printing at all.
Maybe both cells have it on the back, I will need to separate the cells completely then.
I was actually expecting to see the cells plummet like a rock, but was surprised that
they ran a 55W fog light for 1.5 hours straight until they hit 3V and all 4 cells stayed
pretty close together until near the end, when some stayed at 3.4V a little longer and
two others dropped almost at the same time to 3V.
I will need to measure the exact current draw from the fog light at 15V and charge
the pack back up to 4.2V per cell and repeat.
I'll post pics later, gotta run.

[cor]

Hi Neptronix,
Here some pictures:
The pack and my $11 Battery Voltage Monitor. It is hard to see, but the 2nd cell is at 0.5V and falling...


This is how a good pack looks like - even though it has all the characteristics of a sloppy hand-assembled pack: jagged cut foil, pasted on by hand (that is why the bubble wrap was sticking to it) and the label is sometimes put on one side, other have it on the other, so power wires can come out on right or left side...


The bad pack I tore the label and foil loose, then split the cells apart (did not disconnect the tabs) to look for markings.
As you can see in the picture, there are 4 different printed and hand-written labels on the cell, on top of or under the double sided tape that holds cells together, but not the dreaded Tekocell printing of an old 1C ancient-technology variant of LiPoly. I might actually have a second generation cells or so???


The front of the second (bad) cell.... looking OK, except for the large "fold" in the cell pouch due to the pulling of the double-sided tape and the cell is not exactly straight any longer, it is curved in length and over its width. Not sure if that is going to be a problem in future, because even though the cell was shipped at 0.5V it appears that it is taking a charge and showing reasonable internal resistance, in the same order of magnitude as the other cells...


Just for completeness - the back of the second (bad) cell, again no printing or marking, only pulled together foil from the double sided tape.


OK, now for the kicker:
It seems that the cell was at 0.5V because *it was never charged*!
The manual labor to assemble these packs makes the process vulnerable to error and it appears that they forgot all the normal checks, so one cell slipped through without being charged - ever. And made it into my pack. And that pack was shipped without ever being checked.
Now I hope that the cell can recover from being uncharged for so long - it appears to take a charge (see picture after more than an hour at 4A charging this one cell, it is at 3.8V and it can deliver 5A while sagging approx 0.1V like the other cells.... I will continue the charging to bring all cells in line (there was more than 0.1V of difference between the cells from the start, so I will also charge cell 1 extra - but cell 2 is looking promising, I hope it does not give a pyrotechnics show or develop high discharge or internal resistance - time will tell....

[cor]

There still is something going on with that bad cell - even though I have pretty much brought the pack up to equal voltages (all 4 cells are now between 4 and 4.1V) I noticed that while putting the pack back together that if I press down on the bad cell (or on the entire pack) then the voltage of the bad cell changes.
I am charging the pack at 1A so there can be an effect from changing internal resistance, but I did not see the other 3 cells change at all, only the bad cell showed a drop in voltage (not much, for example from 4.04 to 4.02, pressing harder across the entire length of the pack with 2 hands dropped the voltage to 4.01V). I am surprised to see this in one cell and the others stay at the same voltage. Hmm, maybe I should keep this cell compressed as it has seen some abuse now. Or is there a different effect on first charge of a cell? Or could it be that this cell *is* bad, was originally charged and will soon self-discharge to 0.5V again?
I don't like it when there are so many questions and no answers other than time will tell...

[parabellum]

Or is there a different effect on first charge of a cell? Or could it be that this cell *is* bad, was originally charged and will soon self-discharge to 0.5V again?

I had cells self discharging from start on but still performing well like others in the pack, I cut them out anyway since after few days they are lower voltage and revers charging in use can cost you entire pack or more. Leave it for few days and check the voltage again. 1 of my turnigy cells was loosing ~0.2V per week, so make no conclusions to quick.

[cor]

Hi Parabellum,
Thanks for the advice!
I will write down the voltages of my packs (they are not really well balanced as they arrived) and see if they change in the next days.

[cor]

OK, for your entertainment - here the voltages on the 4 Transmetic 10Ah 14.8V (4s) 10C LiPoly packs:
The first list is from the pack with bad cell 2, which I charged to 4.25V for a short while, now 4 hours at rest
Please understand that I manually balanced this pack already (charging cells individually) because the differences were much larger when I received it.
Originally cell 4 was the highest and hit 4.20V when charging all 4 cells at the same time. After that I have charged cell 2 separately, cells 1+2 and cells 1+2+3 but it looks like I now need to go back to the originally strongest cell 4 and prop it up a little too.
4.163
4.074 <- this cell was at 0.5V when I received the pack
4.173
4.111

This pack had a bad monitor connector. I discharged this pack at 5A, dropping to 4.5A until cell 4 hit 3.000V
Then I recharged the pack back to 16.6V (4.20V at cell 3) at max 8A until current dropped to 1A. No balancing done here (yet).
4.091
4.070
4.136
4.026

The last two packs were untouched, except plugging in the BVM (Battery Voltage Monitor a couple times and
a brief discharge test with the 5A load to check if every cell had decent internal resistance (every cell dropped about 0.1V at 5A discharge)
4.039
4.023
4.009
3.976

4.013
4.091
4.017
4.059

[cor]

Since I discharge-tested the 2nd pack without first charging it, I took pack 3 and charged it to 17V (starting at 4A dropping to 1A at the end), after giving a few boosts to individual cells to better balance them. I did notice that one cell (nr 3) has twice as much internal resistance as the other cells and was the first to go to 4.3V and the lowest on discharge. So, this pack is certainly not going to give high discharge current, but I am not planning to use it with very high discharge, so let's see what the capacity is while discharging it with an easy 5A. I tested my trusty fog light on my power supply to see how much current it draws and it is actually pretty flat, as you might expect from an incandescent bulb: 4.5A at 12V and 5A at 16V.
After an hour it seems that the capacity is not too bad - Cell 3 is still the lowest, but all cells are within 3.59-3.64V.
After one hour, 50 mins the two middle cells are at the same 3.40V level and start dropping faster, the difference with the other cells has increased to 0.1V at that point.
At 1:56 cell 2 is lowest at 3.30V and the difference with cell 4 has increased to 0.15V
At 2 the hour point cell 2 dropped through 3.2V
It reached 3.000V at 2 hours, 8 mins. This means, assuming that current was a conservative 4.7A that the capacity was exactly 10Ah.
Cell voltages at the switch-off moment: 3.31 3.00 3.10 3.37V and as you can see, the middle two cells went down rather close together, while the outside two cells stayed closer to the 3.4V level where the voltage drops less fast.
I am sure that at higher discharge levels, this pack (and especially cell 3) will hit the 3V threshold much quicker, but it is good to see that it has the claimed 10Ah capacity at low discharge level. With the high internal resistance of cell 3, even at full charge level (4.2V) that cell will never be able to give a peak 3C discharge in the first moments before falling below 3V, since I estimate the internal resistance at about 40 mOhm, so 3C (30A) will give a 1.2V drop. Nowhere near the claimed 10C discharge capability anyway.
Funny that while recharging at 10A, all cells are within 0.02V at 3.75-3.77V.
I finished the charging when at 17.1V the charging current dropped to 1A and the highest cell (nr 3) was at 4.304V.
After resting half an hour, all cells are within 0.03V again: 4.236 4.250 4.265 4.234 funny that the first and last cell are lowest - apparently they have larger capacity than the two middle cells. Oh well.

[neptronix]

Those sound like total junk as well.. you might actually have a useable product for non-ebike use.. i on the other hand, have some nice 0.001C cells

[cor]

I might actually try them on my ebike which is an EVG (EV Global) 24V bike that I plan to upgrade to higher voltage in future (but keep current severely limited to avoid burning up the motor, but allow assisting even at higher speeds, since I can pedal faster than the 24V bike will go). That is why I bought 4 packs of 14.8V so I can reconfigure them in 8s2p (29.6V 20Ah) or 16s1p (59V 10Ah). The first variant will never draw more than 1.5C from the packs because the fuse is 25A so peaks of 30A, split over 2 packs, might be light enough duty to use these packs.
For the single series string the current draw might be too high, we will see.

[cor]

I checked the cell voltages on my first pack (the one with the bad cell that initially was at 0.5V) and it seems that it is stabilizing. Initially that cell dropped fast (from the 4.074 after the first full recharge to 3.996 half a day later, but now 2 days later it has fallen only 0.008V to 3.988, while the other cells have fallen by between 0.003 and 0.005V but those were not cycled or completely recharged recently, just a little boosted. I will keep an eye on that cell, but it seems that it has recovered and may even be usable with a good BMS on the packs to keep 'em balanced as they seem not to be to well matched set.

[cor]

One week later and I checked the pack voltages again - it appears that two cells have a self discharge that is not healthy.
Interestingly, this did not show before but started during this week of rest (or showed up while other cells came to rest)
The surprise is that in the first pack, the cell 2 that was dead is now behaving normally. It dropped less than 0.01V during this week
while the cell next to it (cell 3) suddenly shows a 0.08V drop in the same time....
Then there is the third pack with the high resistance cell 2 that also shows up as higher self discharge: 0.06V in a week.
The other cell that was weaker, cell 3 is also showing greater loss: 0.05V while the stiffer first and last cell only lost 0.03V
(Note that part of that loss is due to the cycling and full recharge, causing higher drop initially).
Next week I will start using these packs in my eBike as 8s2p (30V 20Ah) but I will make sure to keep the BVM (Battery Voltage Monitor) with the external (loud) buzzer on them to warn me when they get too much out of whack. And then I'll need to build a BMS...

[cor]

I temporarily installed these packs in my bike (all 4 packs in the box in which they arrived, wrapped in bubble plastic and shoved into the battery tray, then hooked up the 4mm gold connectors with two wires that I attached to the existing bike's wiring. (How do others install batteries permanently? I am wondering how sturdy to make my pack and where to place the BMS once I add it to allow on-bike charging)
Anyway, this weekend I am planning to give a good workout to my packs to see how they stand up to a heavy long discharge on the bike. To do that, I am going to see if they will allow me to climb the Santa Cruz mountains. The elevation of HW9 above Saratoga where it crosses Skyline is almost 2700 ft (900 meters) so just the addition of potential energy during this climb of me + bike is about 320Wh or at minimum 11Ah from a 30V pack, before losses. Since pack voltage will drop, the controller will have losses as well as the motor (each I estimate at 80-85% efficiency) I expect that the pack will just about fully drain on the climb if I do not pedal (so, no assist - just climb on electric power only). Which may be just as well for this test, because if I make a next trip *across* the Santa Cruz mountains, then I will need some extra power to keep the lights going and climb other (smaller) hills, so measuring the maximum drain now will give me that little extra. Good thing that you can always get home on an e-Bike by just pedaling. But to get to the start of the climb in Saratoga is already a 10 mile ride for me, so that alone will be a good workout for me, I won't have too much left over for the climb. Good that the road back is downhill, making this something that can be enjoyed instead of dreaded...

[Hillhater]

..I expect that the pack will just about fully drain on the climb if I do not pedal (so, no assist - just climb on electric power only).

Just remember that running bad cells down below critical voltage under load can result in flames.
..bad experience if you are not close to an extinguisher !

[cor]

Just remember that running bad cells down below critical voltage under load can result in flames.

I will have monitors on every cell, they have a loud beeper that will alert me as soon as the cell hit 3.000V or whatever limit I program.
THere are other issues with the monitors, for that see the thread about the BVM-8S.

[minuteman2k]

Hi peeps

I know you are all smart guys on here !!

If your seeing greater than 20 % volt Sag under full said C Rating something is wrong !!

http://www.giantcod.co.uk/gens-6000mah- ... 06496.html

Here are some of the Best cells i have ever purchased

I can guarantee the cells have super low Impedance less than 1mOHM per cell always

Construction and consistant quality is better than Turnigy which is not hard really

Take a look at Gens Ace Factory its Clinical and efficient to say the least

[cor]

OK, So last Saturday (yesterday) I did climb up HW9 in the Santa Cruz mountains. I got to use about half or a little more electric power and the rest came from pedaling (which I actually liked, I was able to stay in 4th or 5th gear most of the ride up. Not because of battery limit but because the controller on my stock 24V bike would not accept to deliver more than an estimated 400W continuous without protest. I hit the protest more than a few times, but always backed off a little on the throttle immediately to avoid smoking the controller or motor. Result was that I arrived on the top with a good workout and about half the battery power left in the pack. Lowest voltage on the pack was 26.7V (about 3.34V per cell, 8s) which jives with the resting voltage after the ride of around 3.7V on the cells and my earlier measurements of about 0.1V drop for a 5A discharge, indicating that the max draw of the controller is likely almost 20A (about 500W) resulting in almost 0.4V drop per cell.
While the ride up was strenuous but rather quick, I was able to maintain around 10 MPH speed due to the electric assist, the descent was hilarious, reaching speeds of at least 50 MPH seeing that cars could not pass me on the straights and I had to lay the bike uncomfortably flat in even wide turns. For sharper turns I *did* brake, but mostly I coasted down the steep descent (about 2200 ft change in about 4 miles) and I was happy that the packs were able to feed my wimpy e-Bike motor and controller. I doubt I want to pull more than 1C from them though, so these packs are *definitely* not what they are promoted to be, they may be usable for something low power like this...

[parabellum]

22v 10000mah $67 bucks 5c burst 3c continuous sooo... $134 bucks for a 44v 20ah pack @ 3100grams hahaha must be
some good quality LiPO

I don't get the numbers right? My math nust be wrong.
Am I missing something?

Junk I get. Shipping is also another add on. Still cheap and maybe junk.

Dan

How could the voltage of lipo battery can be from 22v to 44v in parallel？

Little buzz and everything looks double.

[neptronix]

How could the voltage of lipo battery can be from 22v to 44v in parallel？

Hit it with a 120v DC power source for a couple seconds. Would be a fitting end for one of these pieces of crap.

[cor]

Anybody having some bad packs that he wants to get rid of?
Bonus points if you have Transmetric 4s packs.

[cor]

Anybody has Li-Poly packs that they can send over quickly? Don't care about condition...

[Grinhill]

You may have better luck if you let people know your location.

[parabellum]

You may have better luck if you let people know your location.

Cor is in (California).

[cor]

Sorry - I forgot to put my location in my profile.
Indeed, I am in Silicon Valley (San Francisco south bay area) in California.
Neptronix has one pack for me, anybody else having packs with bad cells or just unusable packs?

[silverrich1]

I own a crossbow

I have an experiment I'd like to conduct

location: UK, London

PM me if you'd like to see your Transmetic cells receive an arrow through the head

[neptronix]

I own a crossbow

I have an experiment I'd like to conduct

location: UK, London

PM me if you'd like to see your Transmetic cells receive an arrow through the head

Lol, now we have a bounty on them! excellent!