Since it’s my first post here,
Hello everybody! 
I’ve been having one annoying issue with my BLF A6 (3D).
When I use it on my bicycle and hit a bump, the light switches modes (but does not turn off). I use unprotected Sanyo and LG batteries. Is it possible that using protected, longer battery will solve the problem? I do not have one to try that atm but it’s on the way. Any other suggestions what could be done here?
Thanks!
It should be battery length. Try using a magnet to extend the length
Thank you! I will give an update when they arrive
I do not recommend using a magnet to improve the length of the battery as it may shuffle and cause a short.
You can try to expand the spring at the switch or more recommended solder a longer spring to te driver and/or switch.
Thanks, as my manual skill are close to 0 I will try the option with expanding the ring. First test today evening.
I don't think it's caused by the battery, but by the switch which might be pushed by the button. Mine had the same issue.
I think it is a battery length problem, because the battery looses contact to the driver or the button spring for a little moment.
you can put tape, or a narrow nylon washer, or an O-ring around a battery to keep it from slipping sideways and shorting to the tube — with enough bouncing and scraping that can happen through the coating too.
You might look for these other bounce issues
— springs with a sharp tip contacting the cell instead of a long edge — bend the tip away from the cell slightly so more of the spring metal touches the cell and it doesn’t gouge and skip.
— add a dab of conductive grease (“bulb grease” from auto store, or something like that) to the contact points
— make sure the tailcap retaining ring is tight
— wipe all the threads (with conductive grease) to remove the gritty gray gunk (oxidized aluminum wearing off threads)
— lather, rinse, repeat …
Hey CrashOne, could you tell me more about it? Is there a way of fixing it?
Guys, thanks a lot for all the advice.
I’ve expanded the spring and bent its tip a bit, now it doesn’t flicker through the modes so often but it still happens on the biggest bumps (road bike with a rigid fork). I’ve also noticed that if the light is mounted closer to the led and away from the tail it makes things a bit better.
All the threads are as tight as possible. I will try out all the other suggestions until it works. Again, thanks a bunch!
Sounds like you’re getting whiplash — shock through an attachment near the tailcap, then a ‘crack the whip’ effect moving the connection at the head end end.
Could be you have a bad solder join in the driver somewhere that’s cracking from the abuse too. I wonder what an accelerometer would say about how much jerk (technical term, really) you’re imparting.
Or you’re just ‘throwing the battery down the tube’ with that whiplash and over-compressing the spring on the head end so the battery comes off the spring at the tail end.
Can you get the same problem if you just hold the light at the tail end and thrash it up and down as hard as you can?
Like pounding nails with it. Or like shaking the ink into the writing end of a ball point pen, if you’ve ever had to do that to get one working.
You might want to check for dimples in the ends of the battery too.
Though I’m not CrashOne, I’ve had the same issue as he did. This could also be your issue.
Remove the tailcap combination. On the inside you’re looking at the spring, and a brass retainer ring.
Loosen the retainer ring by turning it anti clockwise and remove it from the tailcap combination.
Now you will meet, in order of appearance: the actual switch on a board, some kind of washer, and the rubber boot.
Press the rubber boot inside-out. In the middle you see a piece of it protruding 4 to 5 mm.
Cut off (starting with 1 mm) of that protruding bit with a sharp knife and reassemble the tailcap combination.
In reversed order 
: rubber boot, washer, switch on its board, and the retainer ring.
Make sure to tighten the retainer ring firmly and check what you have done.
Things are OK if you can push in the boot a little(!) bit before it hits the top of the actual switch.
Your issue may occur because the boot is constant pressing the top of the switch, it needs to have the tiniest bit of slack.
What Henk4U3 says :)
Mine was really sensitive, just a slight touch and it would switch modes. That's fixed now :)
Totally different lights, but 30Qs do the same thing in my Convoy C8, and to a lesser extent they also do it in my ThorFire C8. When using protected cells, even directly hitting the butt of the light doesn’t change modes.
The first batch had conical springs on both ends and did not suffer this ailment much. The second batch which mine is had switched to a cylindrical spring at the driver and many have this problem. I don’t know which is in current-production models. The problem is one of length and spring pressure. If you use a magnet it goes on the bottom where it won’t short the cell. Side-play can be solved with a paper-wrap on the cell or adding shrink-wrap to it.
I’m going to mod mine with better springs (it gets a spring-bypass then too). Not a huge problem going up the modes but when it rolls back to ‘moon’ it’s super frustrating leaving you essentially blind till you ramp up to a higher mode again. There has to be some ‘looseness’ for longer protected cells to fit and using those can also provide a solution to both length and width issues too.
The “BLF A6 Trouble-shooting and Mod” thread is huge but worth the read, and Dudunphy has done a wonderful service for us by compiling the info up to the top of that thread. This is a great light with few flaws and just about every problem you may have with it has a simple and easy solution. It’s now my second-most used light and almost tied for first place.
Phil
Hi again,
I bought a magnet and finally had the time to test this weekend - the problem disappeared! If it occurs again I will do the tailcap thing.
Thank you all for the advice!
BTW - there was no way I could make the light switch the modes by shaking it, even before using the magnet. The only way to force it was to hit a bottom of a thick plastic bottle.
Basically, on a bike, it’s the same problem that can occur with a gun mount. Lots of shock. Heavy springs at each end.
Another update, should somebody have the same problem - I tried it with protected battery, which is a bit longer and thicker (Keeppower 3100mAh) and it works perfect. Of course, there is no need for magnets in this case.
Can anyone shed any further light on the magnet fix? I just picked this light up and love it but i am experiencing the same “jolt” problem causing it to cycle through modes while riding. I expanded the springs manually with a pair of forceps and the helped some but it sounds like the magnet trick will truly solve things. I’m worried about attaching the magnet to the wrong end of the battery or potential problems. Any advice would be appreciated.
Dedicated bike lights don’t have this problem because the battery connections are soldered rather than spring loaded. The battery compresses one spring and loses contact with the other so the magnet adds enough length to the cell to prevent loss of contact when one cell is compressed by a bump. A magnet or slightly longer, stiffer springs should do the trick. If barely tapping the switch causes this then either shorten the rubber button cylinder or add a shim to the aluminum button disc. Adding a shim will raise the switch further into the tube and incrementally tighten the springs.
All of my bike lights are one mode .
No more problems .