Protected or Unprotected for 2 cell BICYCLE light?

Thanks to many kind people here,

I am now enjoying daylight at night and am able to cycle in winter due to the headlights
on my bicycle.

All is well except…

The batteries are dying on me like they are disposable batteries! I get about 3 charges before they die.
Shake and moisture seem to be the problem.

They die in various strange ways, flickering, requiring that the torch cap be loosened, causing the charger
to flash alternate red and green….Sometimes they start working again when they have been discharged
a little. But it is stressful.

Today I went over some railway tracks at about 20kmph. It was a bit juddery. I have high pressure tires.
And another battery died. It went all flakey on me…

So I am thinking perhaps protected cells are just not suitable for bicycle lights (for those using high pressure
tires, at a fair speed).

As I say, the lights are great but this is proving to be a NON budget light experience due to the cost of batteries.

My question is…
*If I move to unprotected cells will I be able to keep cycling for longer?
I had a look around the forums first…

For unprotected….

you’d probably want to use unprotected batteries with them.

all I run is unprotected flat cells


I don’t mess with unprotected cells for now, and haven’t had a reason to, really. But from the way I understand it, there’s a certain risk to using any li-ion cell in a powerful flashlight – more if it’s an unprotected cell.

The problem with unprotected cells is not the flashlights you use them in, is to make sure they don’t get over-discharged or over-charged.

With the unprotected batteries i need to be a little more cautious about over-discharging them (because bad things can happen - so I have read anyway).


I’m sure there will be the usual pundits who will weigh in and claim their years of experience with unprotected cells and not a single event. But think of it this way, it takes just one event to potentially alter your life forever, why risk it? Don’t get me wrong, I’m not trying to drum up the hype machine and become the poster boy for safety advocacy, all I’m saying is use your noggin and play it safe.


Well, I certainly appreciate all your advice here people! Ill never use unprotected, and as im starting to read, that the protected batteries are just that, the protection will trigger before the battery blows?

The answer?
BetweenRides (who I know writes very good advice for cyclists)

Personally, I won’t use an unprotected cell unless it is in a light that has low voltage cutoff. These usually ‘step down’ in brightness when the cell is not providing enough voltage, so you know it’s time to change the cell. I use my lights for night bike riding and I carry a spare 18650 with a battery sleeve for just that purpose. Serves the same purpose as the low voltage protection circuit in a protected cell.

If you are not sure about your light or just feel uncomfortable with it, buy a protected cell. They cost a few $ more, but are worth the peace of mind.

Do unprotected blow up?

timtak, I count 4 lights on your bike, which ones are you having issues with? And can you post up a picture or two of the batteries you use?

Protected or unprotected depends on the light. I use protected because I might run the battery down too far and ruin or damage the cell. Thankfully I've never experienced any issues with batteries, but from what I've read, over-discharge can limit the life and if discharged far enough, ruin a cell. In a single cell light, usually all that will happen is you might ruin the cell. In a multi-cell light where the batteries are in series, over-dischargebe dangerous, especially if the cells are not well matched in capacity and charge level. Far more issues happen while charging or through over-charging a cell.

There are plenty of people that use unprotected cells without issue, I just choose to use protected as an added layer of security. Unprotected cells are not inherently unsafer if treated with respect. If it helps any, I do both road riding (Skinny tires at high speed) and trail riding (fat tires but bumpy terrain). It is not unusual for some of my lights to flicker or change modes after a heavy bump. I find that certain flashlights just don't do well as bicycle lights without some modification. If the modes shift or the light cuts out, it is often due to battery slop - either the cell is too small for light (width or length) or the springs in the light are too weak to keep the cells in place. There are several ways to fix this, but it depends on the cells used and the light.

I use disposable batteries on my rear lights

The batteries I am having trouble with are used in my two cell Trustfire TR-3T6 (pictured above and also used on my commuter bike - but not the cateye using AA cells)

and a single cell light UltraFire C8-T6

It was the UltraFire C8-T6’s batter that went wonky when riding over the railtracks yesterday.

The batteries I am using are…

I am not worried about destroying batteries since I go through so many batteries that it will not make a difference.

I am worried about explosions, especially when charging. If they were to explode inside the light I think that the barrel would keep the explosion contained but then if it were to explode through the torch…I would not want that.

By the way, I used to use dollar store recharable AA cells. I presume that they were unprotected. None exploded. Were they a different technology?

There are a lot of people recommending these unprotected batteries at DX
including one person that calls himself “cyclist”. They have no bump at the plus end so they would be good only for my single battery light. But lots of people are recommending them so I am thinking of purchasing some unprotected.

Do I need a different charger? It seems to me that my chargers switch themselves off (the light turns from red to green) but perhaps it was the protected batteries that did that?

Timtak, those Ultrafire batteries are crap. Ok to use in your C8, but don't expect a lot out of them. One of the reasons they are not lasting for you is they are probably used cells with very low capacity salvaged from a laptop and covered with a shiny new wrapper. For your TF TR-3T6, you need to be using good quality balanced protected cells that are evenly matched in capacity and charge state. That is the light you need to worry about. If you were to have an explosion (Not saying you will!!!) inside that light, it can become a pipe bomb. Do not pay attention to the reviews on DX or any other Discount China Light site.

You are in Japan, right? Can you buy 18650 cells from a reputable local shop? If not, I would recommend cells from these China vendors: - Informationen zum Thema solarforceflashlight sales.

What kind of charger do you currently have and do you have a Digital MultiMeter for checking cell voltage?

Thank you.

Pipe bomb!

I am not sure what sort of chargers I have. One came with a light. The other was from DX, Ali, Manafont or somewhere. They both have one or two LEDs. I think that the one with One LED may be charging two batteries as a pair.

I do have a multimeter. I have never used it.

Things are expensive retail in Japan. It is a lot cheaper to order from China and it does not take so long. I see that DX sells panasonics too, very slightly more cheaply. They are about 3 times the price (the Trustfire ones are from about 7usd on aliexpress) but if they last more than tree charges they will be worth it.

Unless anyone has any other advice then I will get some Pannys.

I now regularly use unprotected 18650s. I was ripped off and sold some unprotected batteries as protected. I used them for a while. They worked. They do not appear to get hot. I also find that my other batteries generally die due to the failure of the protection circuit. Thus if I remove it, to create an unprotected cell, that works. My light has not pipe bombed yet but maybe it will soon. Take care.

I’ve been riding my bike with 18650 flashlights for better than 6 year. Not once had a cell died from this.

Unprotected cells rattle a bit more. Both work fine. Today I buy all my cells from Mtn Electronics and I only use XTAR chargers. I also make sure that my flashlights have springs on both ends so they don’t “ghost-switch” modes.

One potential problem I look for is poor solder joints on the springs. These will fail and potentially short on the switch board or the driver board. I simply add solder to the spring and no more worries.

I am glad that someone else uses unprotected cells.

I only ride on fairly smooth roads and don’t get much in the way of ghost switching with flashlights sprung only at the cap.

I go through caps a lot faster than flashlights. I can get flashlights (sprung at the cap only) for about 5 usd a piece on ebay. Cap sellers seem to charge as much for a cap.

timtak those pictures want me to take my bike and go ride right now at night! Unfortunately I got 1 and a half more of winter to wait :slight_smile:

I’d advise getting a proper bike light (yinding, nitefighter, fenix etc) It is an investment you will appreciate over time!

Like this for instance
which are about 20 times the price of the ones I am using (if the link does not work then you may googling vander flashlight ebay, may work)\_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
and for me, and indeed the person that recommended these style of lights to me here on this budget light forum, is that they use only one battery so that one can carry less spare batteries and yet know that one will be always in the sun. I need only one to be seen, which is most of the time, and two to see the road irregularities on the darkest night.

The problem is that I attach them with cable ties because here in Japan there is very little theft. A light that can be easily disattatched may be useful in other places, at least where one is leaving ones bike on the street.

Of course timtak. I started like you too. The convenience of detaching the light easily is a big plus. However, I have found that I need better stuff for faster riding (too much wobbling as you said) and better lighting. There is the yinding also which is on the budget but good quality side.
I am by no means imposing my opinion on you. If that works for you, glad members there could help! Do not upgrade until you think you need to :smiley:

The Yinding looks nice

I started with a Trustfire TR-3T6

but as I got faster I ‘upgraded’ to using two one 18650 cell flash lights so as not to need to carry so many spares. I carry spare batteries, normally two. If I wanted to carry two spares battery packs for the Yinding, I would need to carry the weight of 8 18650 batteries.

I have about 4 cable ties on each of my lights (rather than the metal attachments above) so they do not wobble.

timtak, you must have a strong, flexible back! Given the seat angle vs handlebar height, I’d be in pain in 10 miles with that set up lol.

1) If you’re using unprotected cells in series, you should get a multimeter, even if it is a cheap one. Potentially, (especially if you’re using a generic charger,) one cell can have a higher voltage-> higher capacity than the other. The end result is that if both cells are drained to dead in series, one will be discharged more than the other and can be a fire hazard on recharging. Also, if the charger charges the cell much above 4.20V then it slowly reduces the lifespan of the cell. Having a DMM helps you monitor cell voltages during charging and to ensure that they are the same when you pair cells together.

2) Do you modify lights? If you modify the TR 3T6, with for example a LD2, 2 cell driver or a MTN MAX 2cell driver, you’ll have a lot more output (with reduced run time of course.)

The yinding can be used with a 2 battery pack only! It works fine!! You can check out mtbr forums for more lighting options. Got a great community/reviews there!

Also check out gearbest. They have multiple colours and neutral tint is also available.

timtak, I wont bother giving you a resume but strongly consider the following “your saddle is too high”.

I wont justify it, and you “might” have some one in a million physical defect but if your body is “normal” the saddle should end up about level.

Feel free to ride any way you like, but for your sake consider “trying” your saddle lower and more horizontal.

Point made, end of RANT.



P.S. as you get older your bars will naturally rise to a more typical “drop” almost as if by magic :slight_smile:

hahahah Ronin! I used to have my mtb saddle nose down for a long time and nothing is terribly wrong with it other than the extra pressure it puts on the shoulders…… and having to slide back up the saddle occasionally …Then I got a CF road bike and had to maintain a STANDARD, so leveled the saddle. :stuck_out_tongue:

The frame is way too small for that inseam, at least for me:-)

A larger frame will raise the bar, while allowing you to lower the saddle.