Small Sun ZY-T13 - Battery size issues

I just got this flashlight and I absolutely love it, it has clearly more throw and power than anything else I own and can quite effortlessly illuminate a white line on the road at the end of my street which is about 160 meters away. My problem is that the Panasonic 2900 mAh 18650 cells that are powering the flashlight are too short and rattle around, this wouldn’t bother me but if the light is bumped or one uses it as they walk down the stairs etc. they will cause it to cut out. I’m sure there is a simple solution to this problem but none of my searches yielded any solutions. Would something like a copper coin between the cells and the positive spring allow the gap or play between the cells to be filled? Also a big thanks to ILIKEFLASHLIGHTS for the reviews and advice on the small sun lights.



You need a longer spring on at least one end. Try stretching out the driver end carefully (support base so it doesn’t snap off). Sometimes it’s also possible to remove the metal plunger thing at the tail end and the length of the tail spring might be slightly longer.

Putting some electrical tape inside the tube also helps with the rattling and intermittency.

I just tried the driver spring, but it’s a fairly short spring and doesn’t seem to want to stretch, i’ll take off the tail caps retaining ring and see if the tailcaps spring is longer. Unfortunately i think the rattling is from not enough length because the 18650’s only have about 1 mm or so spare between them and the battery tube. Anyhow thanks for the advice, I will update this in a couple of minutes with the results

Unfortunately my pin nosed pliers have gone walkabouts, and I have no other tools that would be able to remove a retaining ring…. On the bright side I didn’t want to take this light apart anyhow

I found my pin nosed pliers, but the plunger actually added length to the contact so nothing was gained unfortunately, are there any alternatives?

A drop of solder. I have a lot of lights I have had to do that for.

Saint_Jimmy90. Do you own a soldering iron?

If you don't then you can make a spacer out some steel rod.

Not a good idea. The coin (or whatever conductor you try) can slip and you run the risk of shorting -B to +B from the coin to the battery tube. If you put a free-moving spacer anywhere in there, put it on the -B. That way the worse that can happen is the light will remain stuck ON… no chance of shorting in that scenario.

Your best bet is to stretch the springs. I have done this countless times, often times stretching both -B and +B a little each to achieve the desired result. I prefer unprotected cells and have 2-3 dozen Sanyo, Panasonic, sony and samsung… so i have had to do a fair share of spring stretching over the years to get many of my lights to work.

I don’t own one, but my father does and he’s been a tradesman for 35 years so he should be able to help me with any soldering required. So if i get him to try to put an even surfaced do on the tail caps metal plunger that should fix the problem? Does it need to be flat for more contact between the rear switch and the battery negative or does this not matter?

@ kramer5150: Yeah i thought a coin might end badly with the shorting out of high energy density cells, but if i were to try it how would i do it so that so that the light will only remain on as suggested? Im not well versed in any of the technical electronical concepts of flashlights… For the spring stretching though, would it be incorrect to use pliers due the the extra force you can provide or is it basically necessary?

You place the coin on the negative side of the battery right by the tailcap.

Would you believe that the coin will not touch the negative of the battery cell because of the slightly raised plastic layer on the negative end… it must be like 2 tenths of a millimeter but it will not touch and it’s not the coins fault because it fired up just fine with one coin standing vertically in the battery tube touching the negative and the body at the same time….It’s not harmful to hold the coin that’s conducting the electricity is it? Because I did that…… :open_mouth:

I’m working with euro coins just for referance, but would this work if i was able to use a hole saw bit in order to drill out a segment smaller than the current coin and then solder it to another copper coin that also fits the battery tube, because that would allow contact with the negative but also sufficiently fill the gap in order to stop the batterys moving around? Or is that too much effort and solder just makes life easier?

I managed to get a hold of my dads multimeter and so far i can only get tailcap readings and even those mightn’t be correct because on two different lights with different cells i get the same reading….

Edit: Panasonic 2900 mAh 18650 * 2
Small Sun: high .98 amps
med .50 amps
low .11 amps

Ultrafire “4000 mAh”
high 1.12 amps

I couldn’t get medium or low this time.

These seem to be consistent with the other threads, but I still cannot seem to get the voltage of any of my 18650 cells……

These are unprotected batteries?

I would buy protected batteries (wich are logner) and that will solve your issue perfectly. Especially as it highly recommended to use only protected batts in 2-cell lights.

Other solution - mybe additonal (metal) spacer/plate can be put in the tailacap, below retainng ring?

What is the appeal of protected batteries? Im fairly sure mine are unprotected and I have never really thought about getting protected ones, but it might be easier because I need to replace those dodgy ultrafires any how

Its much safer to have them in 2-cell configuration because several reasons. (and theyll fit your flashlight perfectly)

Most bang for the buck youll get if you buy Trustfire “flames” 2400mAh protected from manafont or kaidomain, maybe lightake too (or dx if you like slow shipping and some risk)

can you get panasonics that are protected? I just got a set and i like that they look well made and im a little iffy on trustfires because of all the fakes that were sold to BLF members recently

Protected batteries will prevent a short and also cut off if you try to over discharge a battery. This is good if you want a light that you can just run until it turns off. However they are more expensive. I don't own a single protected battery, all of mine came from battery packs.

If there is a lot of side-to-side slop (I think you mentioned some being there) it can contribute to mode changing. Cut a length of thin cardboard to insert into the battery tube to take up the slop or make a sleeve of paper rolled enough to make a stable fit. Once the batteries aren't rattling you might find that the springs don't need as much stretching as you first thought. Besides that, no one likes to hear a rattling flashlight. ;)

Regarding trustfire flames: Webstores I mentioned, especially kanafont and kaidomain, supply good quality Trustfire “flames” 2400mAh