[Genius Pooh]

http://www.ebay.com/itm/20x-18650-3-...item27c91e8827

At Ebay show amazing cells

5000mah ...wow?

they said It's from japan??

Is this possible?

What is best way check this battery's real AMH?

Hmm very supicious...

[Ziggythewiz]

Shouldn't be too unreasonable. That's less than double where they were 10 years ago.

[major]

Originally Posted by Genius Pooh

What is best way check this battery's real AMH?

Hi Pooh,

AMH I think you mean capacity in Ampere hours or Ah. Please use the correct units.

And the only way to really check "real" capacity or Ah of a battery or cell is to test it. And test a sample lot, not just one. Sometimes you can find independent agency test data.

Also note that Lithium cell chemistry and construction can be tailored to high energy or high power, but rarely for both together in an affordable package with respectable life.

Regards,

major

[PStechPaul]

It seems like a good deal. Maybe too good to be true. 20 pieces of 5 A-H cells at 3.7V is 370 W-H, for $66 including free shipping? That's $178/kW-Hr, which is about half the cost of the Turnigy packs on the Hobby King site.

There's also 10pcs of 4000 mA-Hr cells for $20:
http://www.ebay.com/itm/10PCS-LOT-18...04%26rk%3D1%26

That's $135/kW-Hr. Sounds like an incredible deal. But I don't quite trust them.

[Genius Pooh]

Originally Posted by major

Hi Pooh,

AMH I think you mean capacity in Ampere hours or Ah. Please use the correct units.

And the only way to really check "real" capacity or Ah of a battery or cell is to test it. And test a sample lot, not just one. Sometimes you can find independent agency test data.

Also note that Lithium cell chemistry and construction can be tailored to high energy or high power, but rarely for both together in an affordable package with respectable life.

Regards,

major

Thank you but what I said is just about real test instrument...

What is best and cheap way?

And is it real? 5ah??

[Genius Pooh]

Originally Posted by PStechPaul

It seems like a good deal. Maybe too good to be true. 20 pieces of 5 A-H cells at 3.7V is 370 W-H, for $66 including free shipping? That's $178/kW-Hr, which is about half the cost of the Turnigy packs on the Hobby King site.

There's also 10pcs of 4000 mA-Hr cells for $20:
http://www.ebay.com/itm/10PCS-LOT-18...04%26rk%3D1%26

That's $135/kW-Hr. Sounds like an incredible deal. But I don't quite trust them.

Yeah me too I can't trust them....

Tesla's new car use panasonic 18650 cell 7 thousand..Hmm If this battery is good why they use panasonic's ??

And I heard LG 's best one is just 3.3ah ..hmm

[PStechPaul]

You can fairly easily make a constant current load from a power transistor, diodes, and resistors. Set it for 5 amps and use a datalogger to record voltage and current for one hour or so. I am not so concerned about the actual A-Hr rating, although it is important. But these cells are rated at 1000 cycles, and I'm afraid that well before then, they will start losing capacity or have other problems. And the biggest concern is basic quality of construction and safety. There is a very real "potential" for danger if Lithium cells fail catastrophically. I can draw up a simple load tester if you want to conduct some tests.

[major]

Originally Posted by Genius Pooh

Thank you but what I said is just about real test instrument...

What is best and cheap way?

And is it real? 5ah??

http://www.westmountainradio.com/pro...avcode=/UPSCBA

Get one of these and find out

[dreamer]

Originally Posted by PStechPaul

It seems like a good deal. Maybe too good to be true. 20 pieces of 5 A-H cells at 3.7V is 370 W-H, for $66 including free shipping? That's $178/kW-Hr, which is about half the cost of the Turnigy packs on the Hobby King site.

There's also 10pcs of 4000 mA-Hr cells for $20:
http://www.ebay.com/itm/10PCS-LOT-18...04%26rk%3D1%26

That's $135/kW-Hr. Sounds like an incredible deal. But I don't quite trust them.

Even more unbelievable, these 3600mAh cells are only 50 cents apiece:

http://www.alibaba.com/product-gs/51...y_Yellow_.html

Not only would 5,000 cells give you a 55kwh battery pack for $2,500, but the weight is supposedly only 49g per cell. So it would only weigh 245kg. Doesn't quite jibe with prismatic cells that would typically weigh 600kg for that size pack and cost $20K.

[Ziggythewiz]

Why are you comparing Li-ion to LiFePO4?? It's well known that Li-ion has higher energy density, but the cycle life doesn't even compare. Li-ion can get 300-500 cycles, or some as much as 500-1000 cycles, while LiFePO4 will do 2000-5000.

UltraFire cells have always been cheap, and often live up to their name.