Kokam Rubbish!

[lame_cow]

Had about 5 kokam 2s1p 1500 packs over the past 5 months... And all have ended in this state! Stay away man...

[xhaohaox]

did it melt?

[Art]

did it melt?

maybe you wanna do a search on what li po cells can do when over discharged....

read this

http://www.daddyhobby.com/forum/showthread.php?t=1171

and stop making one liner posts where answers are readily available...

[lame_cow]

actually i hardly used the batteries... just left them lying around and then when i got back to them a few weeks later i found them like that... and even when i did use them they were for FP choppers that can hardly draw 8amps at max throttle?

[lu wei yao]

Thats funny! i have 2 sets that i bought at the same time, used a few times, and kept them for a while. But mine are totally fine. no bloating and such.

[lame_cow]

Haha good for you then..

Well just disgruntled... thats about $250 worth of batteries alone..

[YZY]

Hmm guess u flattened them then left them alone Kokams do bloat like dat dunno y

[edmond22]

I have about 5 of those and I had trouble with one of them only. For slightly more than a year, I think they are quite alright. The one I had trouble with is because I overdischarged the battery and though it didn't bloat, I can smell something sweet coming out from it. What application did you use them on YZY?

[HZM]

What is the charger you using. My understanding that some charger peak at different point and this enuf can shorten its life span if slightly overcharge.

Mike

[lame_cow]

Using Prolux. Very conservative with the battery in terms of discharge, and always leave them charged when storing.

[F/S Eagle Freya]

Storing LiPo batteries

Never store your LiPo batteries fully charges. Discharge them to the discharge cutt off level. Always store this cells in the dischage state. If stored fully charged, the result can be permanent reduction in capacity.


Operating voltage of LiPo batteries;
LiPo Nominal voltage/cell: 3.6V (SAFT), 3.7V (SANYO/KOKAM)

Max Charge voltage/cell: 4.1V (SAFT), 4.2V (SANYO/KOKAM)
Absolute limit: 4.3V

Min Dischage voltage/cell: 2.5V (SAFT), 3V (SANYO/KOKAM)
Absolute limit: 2.3V

I hope this will help LiPo battery users.

Cheers

[X34]

actually i hardly used the batteries... just left them lying around and then when i got back to them a few weeks later i found them like that... and even when i did use them they were for FP choppers that can hardly draw 8amps at max throttle?

How did u store them? ie. If u leave them in the car, this will occur.

[F/S Eagle Freya]

Battery storage cycles

Yes I forgot to mention about the length of the storage. The book says discharge your batteries even if you store them overnight. I find this is overkill as it takes 1.2hrs to charge a 1200mAhr LiPo battery at 1Amp. So if you have 3 cells, then you need almost 4 hours to charge them before you can go and fly. If you are a Sunday flyer and must be at the flying site at around 7:00AM, this means you must wake up at 3:00AM and start charging your batteries. Oh my god, who is willing to wake up at 3AM just to start charging your batteries. So in my personal opinion, if you store your batteries 3 days of more, then I will recommend you discharge them. If storage time reaches 4 weeks, then you have to cycle them. Meaning, charge them and then discharge them for storage again. Do this every four weeks if you store your batteries at an extended time. Cycling your batteries every 4 weeks will takes care of the self-discharge property of the battery. Your LiPo battery has an absolute minimum discharge voltage and you must never g beyond this voltage. Through experiments, 4 weeks is a safe cycle time in order for your batteries not to discharge beyond the absolute minimum discharge voltage.

[lame_cow]

Thanks for the information... Perhaps its my fault after all...

Only thing is i'm puzzled as i store all my other batteries (GWS, polyquest, etecs) the same way too and only the kokams bloat... oh well... lets not brood over this anymore.

Cheers!