flat-top cells in old quark

pomah

Newly Enlightened
Joined
Oct 29, 2012
Messages
45
Hello

I have a QT2L-x, and I want to use flat-top cells in it, is it doable?
 

Hondo

Flashlight Enthusiast
Joined
Oct 26, 2005
Messages
1,544
Location
SE Michigan
The short answer would be no, because there are two pads on either side of the positive contact in the head to prevent reverse polarity. But I do it all the time. I'll explain.

Some people get by this by putting a small magnet on the positive end of the battery to act as a contact, which works. I hate this, especially on a light that uses head rotation for mode selection. Reason is, if the magnet migrates off center, it can make unfriendly contacts that can wreak havoc, and I mean in a thermal sense. Ask me how I know.

What I do, and you need to be VERY comfortable in your soldering skills, is put a little blob of solder on the center of the positive contact of the battery as a permanent nipple. The trick is to prep the battery and the soldering iron properly so that the solder flows onto the battery almost immediately, as lingering can heat the end of the battery to dangerous levels. So you need to assess if you are up to this task. It is much less risky to put a solder blob on the positive contact inside the head, but then you defeat the reverse polarity protection and could fry your light by accidentally inserting a battery upside down.

If you go my route, don't worry about the height of the blob, it does not take much, and if it is too high, you can just file it down to a good height. Keeping the cell cool is the most important factor. If it does not take right away, get off and re-prep the surface. Always clean your iron on a wet sponge, and pre-load it with a drop of solder. It should be very shiny when you touch it to the battery. I always use a thin film of flux on the center of the battery end to ensure the solder flowing.

QT2-L in my pocket now with flat top 17670 done this way. I always run the 2L's on one big cell.
 
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pomah

Newly Enlightened
Joined
Oct 29, 2012
Messages
45
Hmm

Just to be clear we are talking about this type of cell UR16650ZTA, e.g. the sanyo. I was not thinking about soldering. Maybe I should try to order the keeppower from a chinese seller... Noone seems to ship these to sweden... Thank you for both you answers.
 
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