New KeepPower 18350 don't work in series

elzilcho

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Apr 27, 2016
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Just purchased 6 new KeepPower 18350 batteries and they're a slightly different construction than my older generations. The bottoms are now completely flat, lacking the slightly raised platform in the center. The tops are also flatter than earlier versions and are kind of sunk beneath the wrapper. They work fine individually but they no longer work in 2-cell lights because they don't make contact with each other. No raised top + no raised bottom = no contact. Annoying.
 

aznsx

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Just purchased 6 new KeepPower 18350 batteries and they're a slightly different construction than my older generations. The bottoms are now completely flat, lacking the slightly raised platform in the center. The tops are also flatter than earlier versions and are kind of sunk beneath the wrapper. They work fine individually but they no longer work in 2-cell lights because they don't make contact with each other. No raised top + no raised bottom = no contact. Annoying.

Your current observations and assumptions are correct. You want to use "button top" cells in directly connected 2 / multi-cell series applications. Some do use magnets (as OLUMIN indicated). I prefer not to go that route personally and don't recommend it, but some do, and I won't argue the point here. I use button top cells exclusively and don't have anything they don't work in. You might want to explore doing an 'exchange' on the cells you purchased if that's an option, as it would be the 'cleanest' solution, although shipping lithium ion cells has compliance regulations which must be adhered to, and that could make that option less appealing.

Also note that "flat top" cells will not work in single-cell applications in many flashlights (most of the ones I own) due to their dependence on button tops for their implementation of physical 'polarity guard' features.

EDIT: Some also use "blobs" of solder on the terminals of such cells, but I also don't personally recommend that either, but also will not argue the point here.
 
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denenstein

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Sep 4, 2016
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I use 1/4" diameter x 1/16" thick gold plated disc magnets from K&J Magnetics that are $.29 cents each and they work great. You do have to remember that they are there when you remove the batteries for charging, etc.
 

desert.snake

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Magnets are a great and cheap solution, but I lost them so often that I just now drip on the flat "plus" a drop of solder, it works fine, but on some cells the solder does not stick, so I use phosphoric acid. But need to use acid carefully, one of the cells deteriorated, since I dropped too much acid and did not notice it, it imperceptibly short-circuited the battery and the battery quickly discharged to an unrecoverable state.

In some electric workshops, they offer inexpensively a service for spot welding of battery leads, you can ask them to weld a suitable metal piece on "+" batteries so that it protrudes enough.
 

denenstein

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Sep 4, 2016
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The solder would need to be no lead that consists of tin - copper - silver or you might get an oxidation on the solder which could introduce some resistance in the circuit which would not be a good thing. At $.29 cents per magnet it is no big deal if you lose a few and the gold plating makes sure they conduct electricity well
 
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