# Thundersky LCP & LMP cells



## SolarJ (Sep 12, 2009)

Anyone know anything about the other LI chemistries that are on the Thundersky web site? Looks like both LCP & LMP are lighter / wh than existing LFP types. Are these any good for EV use?

Thanks, Jim


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## TheSGC (Nov 15, 2007)

SolarJ said:


> Anyone know anything about the other LI chemistries that are on the Thundersky web site? Looks like both LCP & LMP are lighter / wh than existing LFP types. Are these any good for EV use?
> 
> Thanks, Jim


The other chemistries are not EV friendly. A few years ago a group of people bought the LCP and they were destroyed in matter of days because they cannot handle the same use as the LFP.

The LCP cells have a max discharge rate of 0.3C or 30 AMPs for a 100 AH battery, where the LFP are 3C, or 300 AMPS for a 100 AH.


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## SolarJ (Sep 12, 2009)

Hmm. Thats not what the web site says. I wonder if they have made some improvements? 3C for both max discharge curves. Not that I would even need 3C at High voltage though. 90AH is the same weight as 60 for the LFP. My controller max is 250A @ 370VDC. I am ok with .5C max charge rate. Since I am HV. I see 30-40A as the max from a 50A 240VAC charger.

Thanks, Jim


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## TheSGC (Nov 15, 2007)

Read this: http://www.casadelgato.com/ThunderSky/

There is a reason why you do not see LCP cells for sale on EV suppliers websites, and only LFP or other Lithium Iron Phosphates, because that is the chemistry that can take repeated abuse.

It's up to you what you get, but LCP track record is so poor that I don't think anyone has a working EV with them. On the other hand, LFP have been proven to be extremely EV friendly so far, and some people have a few thousand miles on them.


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## MN Driver (Sep 29, 2009)

TheSGC said:


> Read this: http://www.casadelgato.com/ThunderSky/
> 
> There is a reason why you do not see LCP cells for sale on EV suppliers websites, and only LFP or other Lithium Iron Phosphates, because that is the chemistry that can take repeated abuse.
> 
> It's up to you what you get, but LCP track record is so poor that I don't think anyone has a working EV with them. On the other hand, LFP have been proven to be extremely EV friendly so far, and some people have a few thousand miles on them.


Lithium Cobalt itself doesn't share the reputation of the Thunder Sky group buys that were 2005 and prior. I'm convinced that Thunder Sky has improved since then but based on the spec sheets provided by Thunder Sky themselves, I would look for a different brand if you want something other than LFP because there is much better options out there. I know one person in the UK who was satisfied with the LCP (originally just called LP) cells and got a decent life to the end with them, even at the £4750 cost he paid for the 108 volts(30) of the 200Ah cells. He used the pack until it reached the end of its life. The end of its life was determined by its increasing voltage sag under load to the point where the pack was no longer useful.

I think they have improved but I don't think they are as nice when comparing them with the LFP specs provided by the same manufacturer. Thunder Sky LMP cells are rated 300 cycles at 80% DOD and 500 cycles at 70% DOD, so I wouldn't buy LMP cells. I wouldn't buy the LCP cells because when I look at their temperature versus discharge rate charge, they look unable to provide the amount of amperage you would need at a respectable voltage. Their LCP cells are rated at 2000 cycles at 70% DOD and that will likely be less with higher discharge rates than the C/3 that they are rated for, I would avoid pulling the 3C charge from the LCPs especially if they start getting warm, which they likely will get warmer than these LFP cells based on the discharge charts because they look to have more internal resistance to them.

Keep in mind that Lithium Cobalt is the a very energy dense chemistry but if you discharge below the minimum threshold, even under load, or charge beyond the recommended voltage, you risk burning your car to the ground. There is a debate going on over here with LFPs having battery monitoring, with Lithium Cobalt, there is no debate, YOU DO IT or once you drop below the minimum safe voltage on a cell, you discard it, you don't charge it or you risk high pressure fire, same with going over voltage, high pressure fire. ...same goes for charge and discharge rates and temperature. Lithium Cobalt is safe as long as you don't stray from the provided specs but you have to keep a close eye to be absolutely sure you don't.

Would I use Lithium Cobalt or Lithium Manganese in a conversion? I would! Would I use Thunder Sky? Only for their LiFeYPO4 cells.

One more thing, LiFePO4 has been accessible and cheap under multiple brands, Lithium Cobalt and Lithium Manganese aren't at the same price range. You can check with EVComponents to see if they can toss them in their boat freight and what price they might cost but I have a feeling they will go for more money than what we are already actively getting.


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## SolarJ (Sep 12, 2009)

Thank you for the a great reply. Can you recommend a specific Lithium Cobalt battery manufacture that might be good for EV use?


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## MN Driver (Sep 29, 2009)

One of the more commonly mentioned name that seems to have a good reputation is Kokam http://www.kokam.com/english/product/battery_main.html

I've looked into their specs, statements of safety, their comparisons to other cells and based on what information that I -used to find- provided by the manufacturer these looked amazing but for some reason I can't find those comparisons anymore and I thought they used to say they were good for thousands of cycles but now I look and it says 80% DOD >800 cycles and the site looks much less professional that I remember it. I'm not sure what changed, maybe they are just getting more realistic to their numbers but it seems that most of the talk I come across on these cells they seem amazing.

If you only need 1C constant current discharge and 2C peak discharge and are okay with 1C charging and a very high price relative to the LiFePO4 most of us are considering, they might be the wonder of Lithium energy density. Their 240Ah pouch cell for example is 455mm wide, 325mm in length, but only 17mm thick. They are meant to be stacked so they are larger but in the end take up less space. Victor T from Metric Mind has put together many Kokam 40Ah cells to make a very high voltage(in standard DIY EV standards) pack and he speaks highly of them after getting burned badly on one of the first US Thunder Sky group buys. I'm not sure what he replaced his Civic pack with after he found out they were junk, I wish he updated the Metric Mind page but he said in another forum that what he put together was just an example and didn't want to turn that part of his site into an area of complaining but I am curious what he ended up using in that car though before he started with the Audi with Kokam. ...back on topic, with the Kokam cells it requires more work than prizmatics because you need to house them in a way to protect the pouches and source the power from the tabs but if you have the resources to do something like Victor did, you can heat them so you can charge them and cool them for when you are utilizing more of their performance. Don't forget that you should never charge a Lithium Cobalt below freezing. I personally have killed a cell phone battery in short order doing that once at 10 degrees F when I plugged my cell phone into my car charger and walked before going into work one day, that battery went from lasting a day on a charge to dying 5 minutes into a phone call with a fresh charge.

I'm going into more detail than I need to and I won't claim to be an expert on the actual brands themselves and I strongly encourage you to do your own due diligence and do plenty of research on different brands and trust your gut when something doesn't seem right because Lithium Cobalt, or any vehicle battery purchase for that matter is -very expensive-. My personal opinion on battery brands for Lithium Cobalt is limited and I can't claim to be an expert on comparing them. I suggest going through EV Album, searching through and looking at different Lithium battery manufacturers that people are using and send some emails to people who have racked up alot of miles asking how they perform for them and what they think. ...one thing to be careful of, for some reason LiFePO4 cells seem to be labeled as Lithium Polymer there instead of LiFePO4 so before you send an email take a look at the web site of a manufacturer to be sure you are actually looking at Lithium Cobalt. Also, don't put your purchasing decision solely on the opinion of one person either, get multiple opinions if you can find them as there are too many companies out there, many in China and other countries far away that would be glad to take your money and send you something resembling refined garbage. Even US companies, which I won't name names as I think I've seen their ad on this site have released cells in multiple chemistries that don't perform to spec in more ways than one.

I wrote a novel there, I hope I didn't write too much, but I wanted to cover as much as I could. For a bit of personal opinion, which varies alot depending on who you talk to: Due to the cost, my tolerance for energy density, and my personal willingness to take a risk, I'm probably going to stick with LiFePO4 and in the few years that I have before I have comfortable resources to do a conversion, which will also let me see how Thunder Sky performs over time, I will probably go with Thunder Sky LFP cells. I will also likely be oversizing my pack to allow for their eventual decay and also likely doing things that most other people on this forum don't do or aren't willing to do to prolong those cells, which includes building a sealed insulated and heated environment(with warm air as opposed to under cell heating) for them so that I'm not charging the cells or discharging them below freezing. It might be overkill to most but I'm the kind of person who would prefer to treat them as gently as possible for maximum life and if I was going with Lithium Cobalt keeping them above freezing and within the proper specs would be a must but I think that it would benefit the LiFePO4 cells as well to treat them the same. Of course there is debate on whether or not such things will benefit LiFePO4, I'll leave that to the threads that debate it and take methods that protect other lithium chemistries and apply them to LiFePO4 since I see no downside other than a little extra space and effort to carry those out. ...and I'm not discussing BMS systems when I compare Lithium Cobalt and LiFePO4, I'm specifically talking about the other aspects as I think that Lithium Cobalt without a BMS is very stupid considering the fire risks, extra fragility to stability, and the extra money involved in LiCo and I do see that for many people, since LiFePO4 doesn't seem to become unstable(or as unstable) and unsafe when its faced with negligent death, that they would be fine without it, but use one with LiCo if you go with LiCo. I'd like to avoid the voltage sag and be able to charge them without concern to waiting for them to heat up or wonder if they will get a full charge or not too. I've said alot so I'll stop here.

...but do utilize this resource for seeing the different brands and chemistries available because this does contain most of what is out there for cell brands, a great deal of resources comparing BMS systems too for those interested in the details of the many different systems.
http://liionbms.com/php/cells.php


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