begging for a spreadsheet…. i know some do not have excel but open office is free and i think it would solve a lot of organizational problems. my apology if there is a spreadsheet in here somewhere i just could not wade thru it all
32650 and 26500 will be added tomorrow. If anyone has any further suggestions post here or PM me. Also, if someone can clarify what is wanted in a spreadsheet that would be appreciated.
Choosing batteries: Scaru, could you please point out to beginner purchasers that that there are three main types of contact points on the positive end. Flat, button and nipple. The “button” term can be misleading, because its generally used to describe both button and nipple. Some flashlights with reverse polarity protection such as Eagletac, require nipple tops. A nipple top has a smaller diameter button than a true button top and is usually raised up a little more.
It is good to double check when purchasing, because photos of button tops sometimes make them appear to be smaller in diameter and result in awaiting a new battery only to find it will not work without the aid of a magnet.
Ok, done with the larger cell section unless anyone has any requests. I added this info about button tops and magnets.
"There are 3 main types of positive contacts used on the batteries. First, and most common is flat top; these are a simple metal contact no higher than the surrounding label. This is the way batteries generally come from the manufacturer. (Does not apply to NCR18650 series) Then there is raised top, or button top, this has the same contact size as the previous one, but the whole surface is raised. This is needed in lights where the batteries are stacked to ensure contact. Then there is nipple top, this has a small raised top; much smaller. Some lights that have mechanical reverse-polarity protection require nipple tops.
People often use small round magnets to create a a nipple top from a flat top. To do this one simply places a magnet on the top of the battery, this does come with a risk. The magnet can easily slide out of space and short out the battery, it is for this reason people often place a dab of superglue under the magnet. An example of one of these magnets is this. "
And I'll ask one last time, what would you guys like in a spreadsheet?
What are the temperatures Lion batteries should be used in?
I’m mainly interested in what is considered safe and normal for the 18650 cells while charging and discharging them, what temperature raise in these conditions is tolerable.
What are typical internal resistances of different Lion cells?
18650s, 26650s
When are they good, when bad?
Got this yesterday from some other place:
Resistance
Condition
## - 150 mOhm
Excellent
151 - 250 mOhm
Good
251 - 350 mOhm
Marginal
351 - Up mOhm
Bad
My 18650s raise by 4-5°C while charging at 0.5-1.0A, they are old Sony US18650GR cells, testing them and so far it seems they may have 1700-2000mAh from the stock 2400mAh and have internal resistance around 30mOhm. I find them not very good. Higher drain and charge rates are a no go for them I think. They lasted 5-10min in my laptop. Slow charge and discharge (0.5A) seems ok though and causes no heat up and capacity seems usable as well. I suspect they may be getting overcharged, right now it shows 4.19V when pulled out of the charger, while in charger and charging the voltage shows 4.24V and charger shows 4.1V and balance shows also 4.1V. Still charging them 0.3A. My DMM is not calibrated and I can’t figure out a way to get something that I could calibrate it to.
I’m trying to test all 6 cells and determine their capacity. Should I be worried about them raising their temperature +5°C? What about +10°C? The cells don’t go over 35°C.
Generally between 20 and 40 degrees Celsius for maximum capacity.
The raise in temperature is due to the increased internal resistance. It causes some of the energy used to charge the battery to be lost as heat. One can find the internal resistance of a cell from HKJ's tests. For example the NCR18650B has a .11 ohm internal resistance. Most LiCo cells have a internal resistance ranging from 9 to 20 mohms.
30 mohms is definitely more than a good cell would have but is still usable, just not at high currents.
It makes sense that they cannot handle high drains as the increased internal resistance means that less current would flow. What charger are you using?
I've started to write my own articles for BLF, but it is hard to compete with flashlightwiki. In total the three of my articles are something like 100 pages.
