Step 2: Cells
The words batteries and cells are used interchangeably but the difference is that a cell is the most indivisible part of the battery which stores power and a battery can be made of many cells. This battery is made of 16 cells. The configuration is called 4S4P. That means 4 series and 4 parallel. 1S4P means the capacity is multiplied by four but the voltage remains the same. 4S1P means capacity remains the same but voltage is multiplied by four. 4S4P mean this is a battery 4 times the voltage and 4 times the capacity of a single cell. The newest 18650s are 2.6 amp hour. 4S1P is 16.8 volts and 2.6 amp hour. 4S2P is 16.8 volts and 5.2 amp hour. 4S4P is 16.8 volts 10.4 amp hour. Given that these are used batteries I will give it a more modest 8 amp hour rating. 18650s fall to 80% capacity after 200 cycles. You could test the exact capacity on yours if you had a watt meter.
The cells are a common format, and therefore widely available and cheap, called 18650s because they are 18mm by 65mm. They use 6800 18650s in the Tesla Roadster! My brother works at a university where he has access to an e-waste dumpster. Old laptops are often powered by these cells. Often you can look up the date of manufacture and capacity by looking up ID numbers on the cells. There is no way to tell how many cycles they have been through but the savings are so great over new ones that it is easy to ignore most lack-of-charge problems.
There are 18650s all over the net which claim capacities all the way up to 4.2 amp hour and they are half the price of the ones on batteryspace. The highest capacity 18650s on batteryspace is 2.6 amp hour. I called a tech guy and asked him about these 4.2 amp hour Ultrafire 18650s. He said he never heard of Ultrafire and that 2.6 amp hour cells have been the industry standard for years. I haven't tried the Ultrafire batteries and I am not sure if they would work for this project. You can read more about them on Candlepower Forums .
New cells are 7.25 dollars each new on batteryspace here so I saved 116 dollars by finding used ones. If you can't find old batteries for free you can sometimes find used 18650s on ebay.
The cells are a common format, and therefore widely available and cheap, called 18650s because they are 18mm by 65mm. They use 6800 18650s in the Tesla Roadster! My brother works at a university where he has access to an e-waste dumpster. Old laptops are often powered by these cells. Often you can look up the date of manufacture and capacity by looking up ID numbers on the cells. There is no way to tell how many cycles they have been through but the savings are so great over new ones that it is easy to ignore most lack-of-charge problems.
There are 18650s all over the net which claim capacities all the way up to 4.2 amp hour and they are half the price of the ones on batteryspace. The highest capacity 18650s on batteryspace is 2.6 amp hour. I called a tech guy and asked him about these 4.2 amp hour Ultrafire 18650s. He said he never heard of Ultrafire and that 2.6 amp hour cells have been the industry standard for years. I haven't tried the Ultrafire batteries and I am not sure if they would work for this project. You can read more about them on Candlepower Forums .
New cells are 7.25 dollars each new on batteryspace here so I saved 116 dollars by finding used ones. If you can't find old batteries for free you can sometimes find used 18650s on ebay.
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I HAVE found some 4200mAh rated 18650 cells, but they were Ni-MH(like here http://www.all-battery.com/browseproducts/One--4-3-AF-%2818650-Size%29-4200-mAh-high-capacity-NiMH-battery.html).
Those are completely different animals from Li-Ion 18650s.
You COULD use them for the same style project, but you'd need a different charger/charging setup.
Not to mention, they are still 1.2 volt.
So to get equal capacity...
for every two 18650 Li-Ion cells(we'll use an "average" 2600mAh@3.7v) you would need 3 18650 Ni-MH cells.
2x2600mAh@3.7v = 5200mAh@3.7v
3x4200mAh@1.2v = 4200mAh@3.6v
Trade offs are, safer to use/charge, but more weight, more space, less capacity, and good luke finding cheap/free Ni-MH.
were the ones i was looking at to me it says 10x 18650 at 5000mah but it could also be 10 18650 5000mah total.
just depends id wording is right
With all the components for the summer project, my setup totals $200 plus unknown shipping for some things.
If the batteries are found in laptop batteries, why not buy some of the mass-produced laptop batteries, take them apart, and save a few bucks over buying new individual cells?
for example, buying 3 dell 11.1 volt, 4400 mah laptop batteries would cost $52 and gives 2 extra cells in case of a dead cell.
link: http://www.amazon.com/Dell-Inspiron-1545-Laptop-Battery/dp/B002MG6OO6/ref=sr_1_4?s=pc&ie=UTF8&qid=1366750261&sr=1-4&keywords=dell+laptop+battery
Individually, the best price/quality I could find was trustfire @ $5/cell with unknown shipping cost, which adds up to $80 plus shipping.
these would make a hell of a mp3 player battery lol