whats about KOKAM??

R

RoughRider

100 W
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May 17, 2009
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whats about KOKAM?

i just found only 2 topics about KOKAM...

i heard alot good stuf about KOKAM...why are kokam cells not used here?? they have very nice cells and they are not as expensive as BMI...

so, whats the problem with KOKAM cells??
 
I'm no sort of battery chemistry expert, but Kokam is suposed to kinda be like the LiPoly equilivant of the Kinions chemistry, at least that's my weak understanding of it.

They are suposed to be safe to overvolt with no danger of fire, safe to stab and crush etc etc.

They also make some 8Ah cells, 20Ah cells, 40Ah cells, 70Ah cells, 100Ah cells, and even 200Ah cells. All pushing Wh/KG levels way beyond any LiPO4 stuff.
 
Scroll to page 12 of this .pdf and you can see some of Kokam's claims, and the difference between there cells and conventional LiPoly.

http://kokamamerica.com/kokam_catalog.pdf
 
So now I am confused !
Safe Li POLIMER??
Safe to overvolt, safe to subject to 150C temperature?
Safe to drive nail through them?
Smebody explain?
MC
 
Ypedal said:
I've been eyeballing these for many years already... it is indeed strange there is virtually no mention of them on the ebike forums...

Are they that much more expensive ? am i missin somethin ?
Click to expand...

I am aware of two builders who have assembled large format Kokam packs for street EV's.
One noted that Kokam had assured (not guaranteed) he would achieve 800 80% DOD discharges before losing 20% of the capacity.
His actual experience was that the cell impedance doubled well inside of 400 cycles, resulting in some additional energy loss (as heat) while accelerating.
Granted, this information is now 24 months old and may not be indicative of recent results.

I have been told these cells also have a somewhat short chemistry life at 5 yrs before a considerable capacity percentage is lost.

These folks at the link below have been using Kokam's for awhile, and may provide some honest feedback about the cells:
http://www.proev.com/

There's a FL tel number listed at the bottom of their battery page.

Regards, Jeff
 
The proEV team that uses Kokam's said that the cells cost between $1.70-1.88 per w/hr.

However... That was 4 years ago when they bought them. Regular RC lipo packs had about 4x the internal resistance and less capacity 4 years ago, and most were $3-5 per w/hr.

Now, times have changed. The Ri is so much lower, the pack they built would only be seeing about 1/4th of the heating they were dealing with under discharge, and RC LiPo can commonly be had for around $0.58 per w/hr now.


So... The market trend has cut RC lipo prices by about 80%. If Kokam's prices on cells followed this trend, they would be about $0.35-40 per w/hr, but Im sure that's just wishful thinking. I'm guessing they are at least under $1 per w/hr now days.

I'm liking the idea of a large format 40Ah safe 10c LiPo cell for E-bikes. 400amp ability, way way better energy density than LiFePO4, and the pack construction would sure be easy to just make a single string of cells.

Then the LiPo haters could quite fussing about how LiPo creates atom bomb blasts that level your whole city, and are the reason children starve in Africa.
 
RoughRider said:
whats about KOKAM?

i just found only 2 topics about KOKAM...

i heard alot good stuf about KOKAM...why are kokam cells not used here?? they have very nice cells and they are not as expensive as BMI...

so, whats the problem with KOKAM cells??
Click to expand...

Kokam do not make safe LiFePO4 like BMI, A123 etc. Li-Po is potentially very dangerous.
So BMI is not so expensive if you must replace your entire e-bike because it has gone up in smoke and flames.
Pretty typical of the sort of fire which can occur is the following (in this case from France but I see similar photos from all around the world). So in the end it it entirely your choice if you want to take the risk of being in the "hotseat" (literally!)
http://video.google.fr/videoplay?docid=-1086364983225733633&ei=HSauSY2NCIKywgOP8_CnDg&q=mon+v%C3%A9lo+part&hl=fr
 
liveforphysics said:
The proEV team that uses Kokam's said that the cells cost between $1.70-1.88 per w/hr.

However... That was 4 years ago when they bought them. Regular RC lipo packs had about 4x the internal resistance and less capacity 4 years ago, and most were $3-5 per w/hr.

Now, times have changed. The Ri is so much lower, the pack they built would only be seeing about 1/4th of the heating they were dealing with under discharge, and RC LiPo can commonly be had for around $0.58 per w/hr now.


So... The market trend has cut RC lipo prices by about 80%. If Kokam's prices on cells followed this trend, they would be about $0.35-40 per w/hr, but Im sure that's just wishful thinking. I'm guessing they are at least under $1 per w/hr now days.

I'm liking the idea of a large format 40Ah safe 10c LiPo cell for E-bikes. 400amp ability, way way better energy density than LiFePO4, and the pack construction would sure be easy to just make a single string of cells.

Then the LiPo haters could quite fussing about how LiPo creates atom bomb blasts that level your whole city, and are the reason children starve in Africa.
Click to expand...

The words "safe" and "Li-Po" don't go together in the same sentence and by the way I am not a Li-Po hater. They are great for high power applications in small format batteries such as for RC model aircraft. But for anyone who considers using them in a full scale EV application they must have a death wish. There is good reason large format Li-Po cells and batteries are strictly prohibited from being transported by aircraft by international air transport regulations while LiFePO4 are safe/permitted for air transport. It would only take one or two major fires in EV's to scare the general public that electric vehicles are not safe and put back all the good which has been done in promoting EV's as the way of the future.
 
I am not drawing conclusions. I have seen the results of the fires (numerous photos and videos sent to me) and have spoken to model aircraft owners who have had their aircraft go up in flames.
I looked into Kokam in some detail several months ago so by all means please correct me if they have come up with something safer in recent months which is not LiFeP04.
Sure I agree entirely that lithium manganese is much safer but why would you consider using a battery with a max cycle life of no more than 500 cycles compared to LiFePO4 which has a cycle life of 3-4 times that.

If Kokams (or similar Li-Po) are so safe please send me the MSDS for the cells showing their approval to be transported by air?
 
The Kinion cells use LiMn rather than LiCo. They have a voltage advantage and capacity advantage over LiFePO4. They are also equally safe. They are even more safe than A123 LiFePO4, which is why the Volt project switched from A123 to a LiMn based cell from LG. More energy density, and more saftey.


I have been under the impression for a few years that Kokam cells used LiMn chemistry with a polymer electolyte rather than a liquid electrolyte.
 
Lets use the example of RC model aircraft for a moment since both Li-Po and LiFePo4 batteries are used for this application.
I have heard and seen lots of cases where such batteries have caught on fire in an aircraft but I am yet to see a single case of an A123 powered aeroplane or helicopter catch on fire in the same way even though the batteries are abused and treated just as harshly.
It is not that the Li-Po batteries WILL catch on fire, but rather that they COULD (potentially). It is their inherent danger which is the problem.
It is a bit like saying a pile of gunpowder is safe most of the time but also could be potentially hazardous under certain situations (such as throwing a lit cigarette or match into the pile). Compared to a pile of sand which IS safe when treated in the same way under the same conditions as the pile of gunpowder.
It is all about the fact that something could go wrong because of the chemistry make up, not that is will go wrong.
 
BMI- A123 cells have burst into flames in helicopters. They've also burst into flames while charging. Is it common? Nope! Very rare, but it can happen if the battery has a defect causing it to fail in a particular manner.

You are confusing Li-Co polymer electrolyte cells with LiMn polymer electrolyte cells.

Both appear identical, but there are differences.
LiCo has an exothermic reaction during failure that causes a rapidly self-catalyzing violent reaction.
LiMn has an endothermic reaction during failure which prevents the possibility of a chemical thermal run-away. Yes, any cell can have electrical thermal problems if shorted, and will get hot (like SLA, NiCd, NiMH, LiFePO4 etc etc), but these cells don't go into run-away like LiCo, which is the normal chemistry for LiPoly batteries to use, as it offers the best specific power and specific energy.


I've seen Kokam RC lipo packs for sale before, but I had never bought one, or paid any interest to them, because they never had the same C ratings or quite as high of energy density as the LiCo packs. I'm guessing this is due to the LiMn chemistry not quite being as powerful as the LiCo chemistry. For an E-bike though, I would consider the small loss in performance to use a safe chemistry, and still have much higher power and energy density than LiFePO4.
 
that`s the move clip I saw couple of months ago, from France, said Kokam battery.
kokam PDF specs sheet says Nail Test, 150C Test, etc.
any pictures from Kokam web site.
chemistry is chemistry, unless...
Kokam uses some doping to make them safe???
I doubt.
There are numerous pictures and movie clips on this forum showing how safe grey PSI/BMI/LB cells are.
Same tests on Ping /short, squizzing, etc./ would not bring any fire also.
Chemistry is a chemistry.
MC
 
It often really helps to Google the MSDS for the product, and then Wiki the stuff listed.

http://www.swe.com/MSDS/KOKAM/KOKAM_MSDS.pdf

http://en.wikipedia.org/wiki/Polyvinylidene_fluoride looks like the separator material -melts at 177C degrees, quite a bit better than say polyethylene ......

http://en.wikipedia.org/wiki/Polyethylene melts at 105-110C degrees


So right away we know that thermal tolerance of the KoKams is way better than cheap LiFePo4 with it's low melting point separator.

However, Polyvinylidene when it does burn...... like teflon gives of Fluorine gas, which is way nastier than Chorine..... but that's moot cause it would be burning :mrgreen:

Here is a thread I started https://endless-sphere.com/forums/viewtopic.php?f=14&t=9206 to discuss these separators, as I am convinced they have a crucial safety role.

And LG CPI of the Chevy Volt contract think so too - many of there cells use a Polyvinylidene separator also.
http://www.hp.com/hpinfo/globalciti...roductdata/pdf/ba_lgcli-ion2200_us_eng_v3.pdf

A ceramic coating on the separator (the safety-reinforced separator, SRS) minimizes potential thermal runaway due to internal shorts or overcharges.
Click to expand...
http://74.125.155.132/search?q=cach...reinforced+separator&cd=4&hl=en&ct=clnk&gl=us
 
BMI said:
I am not drawing conclusions. I have seen the results of the fires (numerous photos and videos sent to me) and have spoken to model aircraft owners who have had their aircraft go up in flames.
I looked into Kokam in some detail several months ago so by all means please correct me if they have come up with something safer in recent months which is not LiFeP04.
Sure I agree entirely that lithium manganese is much safer but why would you consider using a battery with a max cycle life of no more than 500 cycles compared to LiFePO4 which has a cycle life of 3-4 times that.

If Kokams (or similar Li-Po) are so safe please send me the MSDS for the cells showing their approval to be transported by air?
Click to expand...

http://www.swe.com/MSDS/KOKAM/KOKAM_MSDS.pdf

Go to the page7 and 8. Yes they can be shipped by air. see also http://www.proev.com/WHistPgs/Hist0042.htm

So what is the separator material in BMI cells?

I could not find an MSDS for Lifebatt, or Headway or PSI yet. Any help apreciated. :lol:
 
so from section 5 and 6 of MSDS is clear :
heated above 70C can release flammable fumes and dangerous substances.
That at just only 70C something can go wrong with Kokam cell - that is bad.
section 6 warns NOT to exceed 60C , it says clearly OPERATING TEMP!!
No wonder they are considered dangerous by many , not by all however.
LiFePo thrives in high temperatures, on hot days inside plastic Abs box they can easly reach 50C.
Kokams are for careful people who carefully consider application, not like LiFePo users.
Again , any pictures of abused Kokams.
look at this forum, you can see PSI cell in vise, dead shorted, abused.
MC
 
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