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ko4nrbs

18650 Internal Resistance Numbers

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This are the Internal Resistance (IR) numbers I use in managing my 18650 cells.

 

50-100 megohm – Excellent (55 megohm new cells (May vary depending on manufacture)

100-200 megohm – Good

200 megohm and Up – Poor (will overheat, may lead to thermal runaway)

 

A new high quality 18650 battery will have an internal resistance under 100 megohms.

 

A used up 18650 battery will have a resistance 400 megohms or more.

 

To ensure consistent readings for tracking a specific cell's Internal Resistance always use the same method and equipment when measuring the IR!!

 

Always monitor the cells external temperature when charging or discharging, especially if it has high IR readings.

 

Bill

Edited by ko4nrbs

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What setting do us noobs use for testing resistance?

 

side note, I disassembled a couple laptop batteries and got some of these out, they seem to charge up fine but the positive end is flat, doesnt protrude out like a normal battery. Seems to work ok in a single battery holder but in a double cell flashlight they dont make a very good connection and blink constantly when moved around. I ordered a few from china on ebay and noticed they have the little rim around the positive end but no vent holes showing, is that bad? The ones I got from the laptop battery have both, the rim and vent holes.

 

Thanks for your work on this stuff

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What charger are you using?

 

All the batteries I have salvaged from laptop batteries have been flat tops with vents.

Mine are of a different manufacture but the top looks like this one:

flat%20top%2018650-_zpssdvsngsl.jpg

 

Most flashlights that use multiple 18650 cells do have connection problems with the Flat Top batteries. Some people have added a small drop of solder on the Flat Top, soldered a small copper or brass disc on it, or used small magnets. I think in the long run you may be better off using Button Top batteries in flashlights that use multiple cells. Lot's safer and more reliable. That said you may find a flashlight out there that can use the Flat Tops.

Check this out:

http://www.lygte-info.dk/info/Battery%20bu...0flat%20UK.html

 

Can you post a pic of the Positive end of your cells?

 

Bill

 

 

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Ive been using a cheapo single battery charger that came with a flashlight and battery I ordered from china on ebay, love the light and it cost around 5.00 just took 3-4 weeks to arrive. Super bright cree t-6 I think. Anyway I just got a Nitecore i2 dual battery charger for these. The cheapo seemed to work fine but could only charge 1 at a time. Attached is a pic of the batteries, the red came from the laptop battery pack, the blue came with the flashlight. Just received 2 black ones like these

 

http://www.ebay.com/itm/3-7V-6000mAh-18650...sid=p5731.m3795

 

but I got free shipping and paid 2.43 total. after I placed the order I got to thinking about all the laptop battery packs we throw away at work and took one apart for the red batteries. Several of those were at 2.6v when I got them out and the cheapo charger wouldnt see them to charge. I put them in the flashlight with a fully charged one and turned it on for a few minutes, I think it partially charged the weak one and then the charger saw them and charged them. Really liking these batteries, trying to figure out what else I can use them for :)

post-314-1447770344_thumb.jpg

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As soon as you get new batteries or you salvage some from a Laptop Battery Pack test the Internal Resistance and record that number for future reference. If it goes up significantly the battery is nearing the end of it's useful life.

 

You'll need a charger that measures the Internal Resistance.

Check out these reviews:

http://www.lygte-info.dk/info/indexBatteri...rgers%20UK.html

 

I prefer Hobby Chargers for measuring Internal Resistance and have two of them.

http://www.hagshouse.com/forums/index.php?showtopic=55215

http://www.hagshouse.com/forums/index.php?showtopic=55207

They are very easy to set up.

 

Read the original post for details. These numbers can vary some depending on the chemistry of the battery.

 

Bill

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