Lipo repair

[suicideneil]

Try Unbelievable rc too, they sell loads of great stuff...

[Metallover]

I found a great website about enerland. I don't know if this has been brought up before, bue here ya go.

http://rclovers.com/WhoWeAre.htm

It hasn't been updated in awhile....

Sent mine out today pimp. I took the liberty of removing the shrink wrap hoping I could see something obvious to fix, no luck.

Thanks.

[brushlessboy16]

Hey Linc, do you happen to still have the Hard cases from eovnu87435ds's RCM packs?

[lincpimp]

Originally Posted by brushlessboy16

Hey Linc, do you happen to still have the Hard cases from eovnu87435ds's RCM packs?

Nope, they went with the cells. They were warped anyways.

[brushlessboy16]

Originally Posted by lincpimp

Nope, they went with the cells. They were warped anyways.

Dang.. its a whole lot easier to reform intact casings then try and fill holes for bullet connectors.

[nitrostarter]

... stupid hard-case rules. Too many chicken-shits think these lipo's are going to just blow-up from riding in the car, WIMPS!

[brushlessboy16]

Originally Posted by nitrostarter

... stupid hard-case rules. Too many chicken-shits think these lipo's are going to just blow-up from riding in the car, WIMPS!

yeah..

the nitro guys think is sooo rediculous that i run 4s.. and its funny when they jump back as you connectors spark when you plug the batts in. :)

[nitrostarter]

I love to scare them with the sparks at first. But when they see it jump out the holeshot and out of turn, they run and hide. :)

[himalaya]

Lincpimp I need a LiPo expert's help.

I bought a Hyperion pack from a stock clearance sale, really a great deal. You know Hyperion is busy introducing their new G3 and trying to close out the old Enerland based packs. The pack is brand new but may have been in store for some time period, I found the pack has problem in cell matching:

Pack: HP-LVX4350-6S, 25~40C 4350mAh
I logged the charge/discharge curve using a EOS0720i hooked to my pc and found
cell 2\3\5 has an internal resistance of about 3mΩ
cell 1\4\6 has an internal resistance of over 15mΩ
in other words, my 6S pack has 3 good 25C cells and 3 poor 5C cell mixed together.
I figured this by calculating the voltage drop during charge pause(3 seconds every minute) and the voltage rise during discharge pause(3 seconds every minute), with same result.

the cells doesn't show too much difference in capacity, all around 3950mAh(set discharge threshold 3.0V/cell) which is obviously 10% lower than it's expected to be(4350mAh).

So my questions are:
* is this problem due to long storage time ? capacity loss and IR increase.
* is there any way I can "activate" the bad cells to improve the IR ? something like high current impact\ slight overcharge/overdischarge or heat/freeze the pack?

Thanks in advance.

[Hardstyle]

lincpimp, have you checked my lipos yet 2 Robbe and 2 MA?

[lincpimp]

Originally Posted by himalaya

Lincpimp I need a LiPo expert's help.

I bought a Hyperion pack from a stock clearance sale, really a great deal. You know Hyperion is busy introducing their new G3 and trying to close out the old Enerland based packs. The pack is brand new but may have been in store for some time period, I found the pack has problem in cell matching:

Pack: HP-LVX4350-6S, 25~40C 4350mAh
I logged the charge/discharge curve using a EOS0720i hooked to my pc and found
cell 2\3\5 has an internal resistance of about 3mΩ
cell 1\4\6 has an internal resistance of over 15mΩ
in other words, my 6S pack has 3 good 25C cells and 3 poor 5C cell mixed together.
I figured this by calculating the voltage drop during charge pause(3 seconds every minute) and the voltage rise during discharge pause(3 seconds every minute), with same result.

the cells doesn't show too much difference in capacity, all around 3950mAh(set discharge threshold 3.0V/cell) which is obviously 10% lower than it's expected to be(4350mAh).

So my questions are:
* is this problem due to long storage time ? capacity loss and IR increase.
* is there any way I can "activate" the bad cells to improve the IR ? something like high current impact\ slight overcharge/overdischarge or heat/freeze the pack?

Thanks in advance.

Hmm, all I can say is to try to run the pack in a low-medium draw situation, and not remove much more than half capacity. Then charge each cell separately and see if they have discharged evenly, if so they should all have lost about the same amount of mah. I would not load the pack too much, as you may damage the weaker? cells... I will be interested to see what you come up with.

Originally Posted by Hardstyle

lincpimp, have you checked my lipos yet 2 Robbe and 2 MA?

Just found them in a box next to the desk so I will take a look at them tomorrow and get back to you. Sorry about the delay, been really busy.

[lincpimp]

To everyone here - I am getting very busy at work, and need a breather from RC. I will be taking a break from lipo repair for a few weeks. You can still ask questions, as I will be on the forum in the evenings as always. You can also send me lipos to inspect/repair, but I will most likely not look at them for a few weeks. That said it is IMPERATIVE that you send full contact info with the lipos if you send them to me. Instructions on what you want done are always appreciated too.

Thanks to everyone who uses my "service" as the money goes back into the hobby and helps me out with my supplies, etc. Just got too much on my plate and need what little free time I have to catch up on my non rc projects.

[himalaya]

Here are some curves to make things clear.



Have a zoom in look


there are two groups of curves, cell 1/4/6 (brown/pink/dark blue) presents far higher voltage under 7A charge current, unless during charge pause period they get close. The "spikes" are 3 second charge pause every minute, you can see the "bad" cells have huge spikes compared to the good cells, reflecting much higher internal resistance.

Now the discharge characterestics, same result, the bad cells have large voltage drop under only 3.2A discharge current. the good cells(red/yellowgreen/light blue) have smoooooth curve(low voltage change when current varies) and are very close from each other, while the bad group are full of glithes and far apart front the good.

[lincpimp]

Well, it certainly seems like those 3 cells are not performing very well. You should not have that much variance between cells. I doubt that they will do very well during a run... Not sure what to tell you to do, can you send the pack back?