Tesla use Laptop batt for $200/ kw so why not we?

[thedarlington]

i read an article a couple days ago about them using 18560 batteries which since are already mass produced for laptops, are significantly cheaper than all other types of batteries, ebikes needing much less batteries, could we tap into this source of cheap lithium batteries? i did a search and they look like 5 AA batteries in a shrinkwrap with terminals at the sides for like $5 , certainly seem much easier to build a pack vs singles, i think its been discussed before, but given the price would anyone else think it may deserve further thinking? after all if tesla's succesfully doing it why cant we

 

[auraslip]

I'm pretty sure they use a much better battery than the standard laptop battery. Just because a cell fits into the 18560 format doesn't meant they perform the same or are even of the same chemistry!

 

[Stevil_Knevil]

Xyster was messing with 18650's -with great success- before the first Tesla even hit the road.

First post in 'Your Creation's Before & After Pics'
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=235&start=0

 

[neptronix]

I believe those Panasonic cells Tesla is using have low discharge ratings, so you need a lot of AH to make up for it..
That's why the car has so much range. ~225 miles!!
It is sorta like the issue with pings. Do you really want to haul a huge 20lb+ battery pack to get decent amounts of amps?

All cylindrical cells have this issue for sure..

 

[John in CR]

All cylindrical cells have this issue for sure..

? Which issue is that. Rectangles pack smaller than cylinders, but Tesla needs that space for cooling. If you're talking about weight, the Konion V cells I use in most of my packs are 160wh/kg, so a higher gravimetric density than the RC lipo packs. They just don't pack as small, because cylinders use a bit over 20% more space. If you mean power density AKA C rate, yes, that's where the type of cells in the Tesla fall down for our use. They use a high energy density cell, but lots of parallel structure to push sufficient amps, because they are low C rate cells. We typically don't need that high a capacity pack for our bikes. They get big and heavy for the amps we want to push. That's not a limitation applicable to cylindrical cells in general though. The A123 cells push plenty of current and my Konions, while not as high a C rate, also work well for even high power bikes as long as you use a pack of 1kwh or more.

 

[Jeremy Harris]

There are already some cheap ebike packs using 18650 cells, but many of them have problems. Search for threads here about Cammy packs, for example, as they use 18650s, as do the VPower ones, I think.

The cells are OK, but it takes time and effort to build a reliable back with them, because of the very large number of interconnections. The cells also need to be securely fastened together, to prevent shock and vibration from stressing all the interconnections, which isn't that easy with a very large number of cells.

Tesla/Panasonic have invested in tooling to build the battery packs, overcoming the connection and mechanical fastening problem. As has been said already, C rates are often limited for this size of cell, but that can be got around by building a large pack. One advantage these small cells have is that they can be fitted into small spaces more easily, so otherwise unused volumes on a vehicle can be utilised for battery space.

I think it would be perfectly possible to build a reliable Cammy-style pack from these cells, perhaps by welding all the cell tabs properly and then encapsulating the whole pack in low viscosity two pack silicone rubber to hold it all together.

Jeremy

 

[dogman dan]

I agree, it's not the 18650 cell format itself that is the problem, but the way the spot welding is done. The notorious 18650 packs from a few years ago were most likely QC regects from the assembly line than made the packs for vendors like Vpower Hong Kong. Cammy cc sold that brand for a time, but the notoriously bad ones were sold by some Ebay character who changed his selling identity monthly. Cammy's were mostly good packs.

This gave all 18650 packs a really bad reputation for a while. Even a good pack could still get pounded in the shipping and pop some spot welds. They most likely have improved the way the cells are glued together into a big pack. You just don't see the guys posting about problem 18650 packs the way you did 3 years ago. In any case though, the round cell pack ends up weighing more than pouch packs. Worth it for A123 cells, but not for cheap 2c cells.

Another example of a good constructed 18650 pack is the power tool packs. Same spot welded construction, but easier to QC with less of them per pack, and obviously higher quality spot welding.

 

[auraslip]

Mmmmm..... somebody should make/design a battery case to hold packs of these cells. Sort of like what you can get for AA batteries at radioshack. Only for 18650s and a lot bigger and more secure.

 

[grindz145]

Mmmmm..... somebody should make/design a battery case to hold packs of these cells. Sort of like what you can get for AA batteries at radioshack. Only for 18650s and a lot bigger and more secure.

These do exist, however, you're better off welding. The resistance of a friction contact like that goes up quickly, and they're bound to fail.

I have 5Kw-h of 18650 based batteries on my bike. If you want a large pack it makes sense. But don't forget, they're also just about the most volatile chemistry. You need backups for your backup cell protection.

That said its also the highest energy density you can get, at least in bare cell form. There is alot of packing necessary though...

 

[neptronix]

Well whatever, i'll take my compact and lighter HK Lipo pack over any of those cylindrical cells any day.

A prismatic battery with a good C rating won't need cooling anyhow!!

 

[auraslip]

neptronix -I made this little calc to compare battery pack prices

Right now it's comparing a 48v10ah a123 pack from cell_man - about 550 shipped including charger - and a 48v10ah lipo pack at "swarm prices" - about $280 including $100 for a lvc and charging solution.

Yes it's half as much, and the a123 2lbs more, but the a123 pack is plug and play and all things being equally, will probably last 4x as long.

Something to think about....

I'm a noob WRT real world costs for charging lipo and lvc - how much did you spend with your setup?

 

[neptronix]

neptronix -I made this little calc to compare battery pack prices

Right now it's comparing a 48v10ah a123 pack from cell_man - about 550 shipped including charger - and a 48v10ah lipo pack at "swarm prices" - about $280 including $100 for a lvc and charging solution.

Yes it's half as much, and the a123 2lbs more, but the a123 pack is plug and play and all things being equally, will probably last 4x as long.

Something to think about....

I'm a noob WRT real world costs for charging lipo and lvc - how much did you spend with your setup?

Bought my 9 5s 5ah 25c turnigy batts for about $378, with $1 shipping for 7 of those and i forget what for the other 2.. so about $390 for the batteries.

Charger was $150, power supply was $50. Miscellany wiring harnesses and stuff was another $50.
That's about $650 shipped, all in all.
And that's a 20ah 36v pack that weighs about 10lbs.

But the price goes down quite a bit when you add more ah.
And i can fit the pack into my triangle frame without having to worry about it interfering with pedaling.
Also, if i wanted to go to 48v 20ah, i am about $170 away from that upgrade.
I could have spent $100 less on the charger too.

Yeah, it won't last as long but the low weight and size seals the deal for me.

 

[Hillhater]

Where does the .." Tesla use ...$200 /kw"... come from ??
Last figure i saw ( has anyone ever bought a Tesla battery ?) was $36,000 for the 54 Kwhr pack.

There are 6831 cells in a 54kw tesla pack,
..so you will need 126 cells for a 1kw pack.
where can you buy these cells for $1.55 each .. ??

 

[auraslip]

Yeah upgrading and swapping around packs sounds like a lot of fun ~~~~

 

[thedarlington]

cant remember what article it was from or find it, its a widely quoted figure probably for just the hardware cells wo control circuits, i was interested so i looked that up for a while, i remember the article mentioned about renaults new electric car and plans for selling it WITHOUT the pack so that its cheaper, leasing the battery from Better place, hugely bringing costs down, which make up more than half the cost of most electric cars, it would be awesome if better place looked into building support for ebikes as well, this sort of business model would certainly push ebikes into the mainstream

 

[neptronix]

Yeah upgrading and swapping around packs sounds like a lot of fun ~~~~

It actually is. All i've got to do is switch wiring harnesses to reconfigure my batteries from 36v to 72v.
That's the beauty of it.

 

[Hillhater]

....cant remember what article it was from or find it, its a widely quoted figure probably for just the hardware cells wo control circuits,

you cannot avoid the reality of data..
for 1Kw you would need 126 cells ( assuming they are 2ahr )
so the cost of each cell would need to be < $1.60 :lol:
Can you or anyone show where those cells are available at, or near, that cost ? ( or at 2Ahr ?)

 

[grindz145]

....cant remember what article it was from or find it, its a widely quoted figure probably for just the hardware cells wo control circuits,

you cannot avoid the reality of data..
for 1Kw you would need 126 cells ( assuming they are 2ahr )
so the cost of each cell would need to be < $1.60 :lol:
Can you or anyone show where those cells are available at, or near, that cost ? ( or at 2Ahr ?)

Standard 18650s are 2.4Ah, the newest from Panasonic are 3.2Ah. The price is in qty no doubt, but I wouldnt be surprised if you could get a group buy to get them down to 300/kwh. There are a ton of costs in assembly and keeping the packs safe though, and I think for ebikes its best that we stay to the low ESR chemistries that are really stable (for hobbiest purposes)

 

[Hillhater]

Standard 18650s are 2.4Ah, the newest from Panasonic are 3.2Ah.
The price is in qty no doubt, but I wouldnt be surprised if you could get a group buy to get them down to 300/kwh.

Well now ? ...are we sure you are talking 18650 ???...

A123 18650 cells are 1.1Ah and...

Nominal Voltage: 3.3V
Nominal Capacity 1000-1100mAh
Recommended Charge : 3A to 3.6V CCCV (constant current - constant voltage)
Recommended Fast Charge: 10A to 3.6V CCCV
Fast charge time: 15 minutes
Continuous Discharge: 30C
Pulse: 60C
Dimensions 18mm(0.72") dia. x 65mm(2.5") ht
Weight: 39 grams
Cycle Life at 10C discharge: 1000+
Applications: power tools, RC racing car, high power EV,etc
Power: Over 3000 W/kg and 5800 W/L

Doc

Even at 3.2Ahr, you will still need 100+ cells.. at how many $$'s for those new Panasonics ???

As for A123 price ... the best bulk deals i have seen were still > $5 per cell

 

[redorblack]

The 18650 cells I've been buying from Deal Extreme are 2.4Ah... but they are also about the cheapest reliable cells you can get at $9.57 a pair. Price drops to $8.18 a pair for quantities of 10 or more... Work great in my flashlights (2 cell 700+ lumen Malkoff Wildcat and a single cell 275+ lumen Zebralight SC60 that is my daily worklight.) I don't know what quantity you'd have to buy to get any sort of quality cell at a significant lower price. The most highly recommended AW cells are $22 EACH.

Here is a link to the cells I'm running that the majority of users recommended on Candlepowerforums.com

http://www.dealextreme.com/p/trustfire-protected-18650-3-7v-true-2400mah-rechargeable-lithium-batteries-2-pack-20392

The biggest thing is to avoid any hint of a bad cell in a high count pack, here is just one story of what damage a bad cell can do in a 3 cell flashlight....
http://www.candlepowerforums.com/vb/showthread.php?t=280909

Here is one on an 8 cell flashlight that did a LOT of damage.
http://www.candlepowerforums.com/vb/showthread.php?t=262234&page=1

Note that none of this has anything to do with soldering tabs either, but the big lesson is NOT to make a waterproof pipebomb and call it a flashlight. In one of those discussions the concept was brought up that high cell count flashlights using these cells really need burst plates for when something goes wrong. When lipo starts off gassing, it makes a LOT of gas really quickly, that is why they have the vents at the tip.

I haven't got a clue how Tesla is making their packs safe, since a bad cell going dead in a pack is usually the start of the bad bad things. I'm assuming that they have everything well vented rather than sealed up tight. I'd love to do a massive pack if it was economical and SAFE. But I know I've got no way of safely connecting cells or isolating a bad cell and safing the pack in the event something goes wrong.

 

[thedarlington]

wow never knew of such a thing even that video that liveforphysics did wasnt that bad and he was intentionally trying to set these things on fire, what was the cause of it? the first seems like 1 was overcharged so with the circuit on, it overfed the other batteries? wahts the possibility of that happening to say lifepo4s? i could just imagine if one of our battery packs blew up at 36v+ and 10ah+

 

[Hillhater]

...what was the cause of it?

...the big lesson is NOT to make a waterproof pipebomb and call it a flashlight.
When lipo starts off gassing, it makes a LOT of gas really quickly, that is why they have the vents at the tip.
.

..ALL battery's release gas when overcharged, usually something flammable like hydrogen, so if you seal it into a airtight (watertight) container .....and include the potential for a spark ..= Bang !
I have donre exactly the same with NiCad's in a waterproof RC truck ....not much left to repair

Motto .. ALWAYS charge batteries in a ventilated area, and do not overcharge them !