cheap, often free, high quality 18650 batts

[lasersgopewpew]

today i was interested to know if i could get some 18650 batteries cheap. i simply walked into batteries plus (any local battery store should do fine) and asked if they had any dead laptop batteries. so he turned around, picked one up from a bucket and handed it to me. then proceeded to ask what i was doing with it. i told him i was going to power lasers, flashlights and such. anyways i opened it up and found 6 red sanyo 18650 batteries. sanyo 18650s reliably produce 2600mAH and can handle high draw, up to 5.2 amps according to their data sheet. i broke out my analog multimeter(i need a digital one) and i had four good batteries, wont know about the other ones until i get a charger. i assume they are dead. chances are one cell of every set that is in series will be dead, unless it is the board that is fried. they will not be protected, but they will be batteries, and they may be free.
just a side note. anyone know if rayfoss is still ignoring support emails about broken lasers. she answers all my questions but i have no idea if it's faona anymore from what i'm hearing.

 

[bluuray]

i got some to.. . but samsung ones..
they where 2.8volts when i pulled them out at first but then i charged them for a few hours and now there 4.2volts (only charged 2 though)

 

[LarryDFW]

A couple of cautions on the laptop batteries.

1. Some of them were recalled (mainly Sony).

2. Life is 5 years from date of manufacture.

3. Life is typically 300 charging cycles.

4. Watch them for the 1st couple of charging cycles,
checking the temperature.

Most used laptop batteries I have checked,
are several years old and down to about 50% of capacity.

Check the IR as described in the sticky post at the top,
to get a better idea of the actual condition.

I do like Sanyo cells.

LarryDFW

 

[bluuray]

how can you test capacity??
and i charged them for hours and they didnt get warm..

 

[lasersgopewpew]

use a digital multimeter to test the draw of whatever you power with them. multiply the draw in miliamp hours by how long it lasts in hours, as a decimal (30 min=.5. if you need help divide the number of minutes by 60 and you have your decimal) and you will have your batteries specific capacity at that specific draw. the slower you discharge a battery the more power you get total. most batteries are tested at .2c, the capacity, ie. 2600mah*.2, or 520 mA for the stated capacity. i hear sanyo makes the best cells
as a side note, i recommend a form of protection for the batteries. i will use a 3.3 volt low dropout regulator. it will lower any voltage from 3.35 to 15 volts, maybe. to a solid 3.3, burning every other volt as heat, meaning the mA in is the mA out, regardless of voltage difference. if you use a input voltage much higher than the output, or you have a higher draw, you will need one heck of a heatsink. sure it is inefficient but when the supply voltage drops below 3.35 volts it cuts off power. if you have to worry about high draw on your cells, you should use a better battery than this.
i have gotten some 18650 battery holders for free from a company called memory protection devices. you can get them here.
Digi-Key - BK-18650-PC2-ND (Manufacturer - BK-18650-PC2) they hold my batteries fine, no guarantees on protected ones, but there seems to be some play in the springs.