High energy cells (specific energy)

[charithjperera]

Hi Everyone,

Would you guys be able to recommend any good high energy density cells?
I'm mostly looking for Li-Ion but the LiFePO4 seem to be very popular here so i'll be willing to take a look at them too. If you can recommend any good distributors of such cells, that'd also be very useful.

As far as the Li-Ion's go, I've come across the NCR18650 and NCR18650 by Panasonic which are 2.9 and 3.1Ah cells respectively with energy densities of ~230 and ~250 Whr/Kg.
Unfortunately I haven't been able to find any distributors of these cells as of yet.

A little bit of context - I am allowed to have 21Kg of the Li-Ion's or 40Kg of the LiFePO4's. This for a solar car race so there's a balance of battery energy vs rolling resistance due to extra weight. So anything good from either chemistry would be appreciated.

I'm also looking at the BQ78PL116 chip from TI for a BMS that I came across in another thread here and i'd be happy to post back with what I end up doing here and how it goes.

Thanks very much!
Charith

Just a quick edit: I actually mean specific energy here, so most energy per unit mass rather than per unit volume.

 

[dogman dan]

My guess is that the easiest stuff to get would be lipo from Hobby King. Maybe not the most dense, but certianly pretty good energy density and very avaliable.

 

[charithjperera]

Thanks for the reply!
I had a look at some of the stuff on the li-po section and they mostly hang a bit below 150Whr/Kg so my aybe a bit low on the specific energy, they have massive power outputs tho so that's still pretty cool!
Our requirements are typically well below 1C but we try to have it rated to 2C where possible.

Just for an update on stuff i've come across, besides for the NCR18650's there's also Samsung's ICR18650-30A with 236Whr/Kg which is pretty sweet.
Now to see if these cells can actually be acquired

Let me know if you guys see anything else tho! i'm always interested in anything cool

 

[dogman dan]

Yeah, it's the aquiring that is often the hard part. On the round cells there may be some extra weight in the metal casings that may affect the "real world" energy density if the specs you are looking at are for just the stuff inside the cans. Heck, even just the metal strips used to connect a herd of little cells may add a lot of weight compared to pouch packs.

Though you may not need the c rate of the lipo, just the fact that they are pouch cells may shave some weight for you compared to any kind of canned cell. They do also sell lifepo4, if you need less touchy recharging.

 

[Toorbough ULL-Zeveigh]

u never heard of ebay?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110591895885/

 

[charithjperera]

Yeah, it's the aquiring that is often the hard part. On the round cells there may be some extra weight in the metal casings that may affect the "real world" energy density if the specs you are looking at are for just the stuff inside the cans. Heck, even just the metal strips used to connect a herd of little cells may add a lot of weight compared to pouch packs.

Though you may not need the c rate of the lipo, just the fact that they are pouch cells may shave some weight for you compared to any kind of canned cell. They do also sell lifepo4, if you need less touchy recharging.

the weight is calculated by just the number of cells * mass on the datasheets; so the masses of the cans aren't too much of an issue. Ideally the weight should be minimised to keep the rolling resistance losses as low as possible but it's probably worth getting more battery power onboard. Cheers for your insights though
Charging shouldn't be too much of an issue tho, we get about 1KW of power into a ~5KWhr pack so the charge rate is about 0.2 to 0.25c at max

u never heard of ebay?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110591895885/

Cheers, I have asked him via ebay earlier about buying 500 for this purpose but I never heard back. Maybe he was unable to supply this much i'm not sure. I might send him another message sometime.
Thanks tho, this could've been a great lead otherwise

I really appreciate the input folks!