Educate Me - Lithium Ion Batteries in Series

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garrybunk
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Educate Me - Lithium Ion Batteries in Series

Ok, I'm a newbie to Lithium Ion rechargeables and want to make sure I have a proper grasp on them before pursuing any plans.  I understand there are protected and non-protected cells.  What complications come into play with running two lithium ions in series?  Isn't there an issue with using protected cells in series?  Do you need to use unprotected cells with a seperate protection PCB for proper voltage rating?  Is a newbie like myself better off using a "safer" alternative?  Aren't there some types of rechargeable lithium ions that do not have risk of exploding and don't need protected from over-discharging or over-charging?  I know there are LifePO4 batteries, but don't think I want to lose the voltage.  


Where I am going with this is that I am considering modding a 2D Maglite with a single XM-L and (2) 32600 cells for maximum runtime, but I'd like to make sure I understand the cells first and am "safe".  I would stick to NiMh, but understand I can't really push the XM-L enough with the NiMh's.

Thanks!,
Garry

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benckie
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if you use full charged batteries together its ok and i would recomend protected batteries, i use lights with 2 x 18650 and 3 x 18650 Lithium Ion rechargeables alot but never mix voltage i use only batteries that are realy close in voltage like batteries that have come off the charger together a digital multi meter is a good investment to play it safe if you want to double check.

DrJones
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Always use protected cells in a serial setup.

Once the first cell is emptied, it's protection circuit kicks in and the light goes out. The other cell might not be empty then, but that's not a problem. 

Essexman
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A popular mod for the 2D maglite is to run it using 3*C size NiMh's powering one XM-L. This requires a mod to the tailspring to fit the 3*Cs, you will need to remove the spring, then using an abrasive remove the finish down to bare metal inside the tailcap, and find a smaller spring to fit inside the tailcap or shorten the mag spring to fit. Then you will need some plastic tube to go into the tube of the maglite to hold the C size cells. 

garrybunk
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How would the runtime and output of using 3 C NiMh's (I'm talking 5,000 to 6,000 mAh capacity C's) compare to 2 32600's?  The 2 32600's should give about 3 hours on high.  Either way I'd have to buy batteries and a charger. 

I'm also considering scrapping the Mag mod and just buying one of these: http://www.cnqualitygoods.com/goods.php?id=1222 which runs on 2 26650's and is rated 3 hours on high. 

I understand now from comments here and from further research that I am ok with protected cells in series and checking them with a DMM (I have two).  Guess the next concern might be the flashlight building up too much heat inside for these cells?

Thanks,
Garry

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