Hello everyone,
I have a Convoy S26a and a S21a on a bike. The S26a doesn’t work well, it changes modes during the session when I go over bumps in the road. The S21a worked well so far.
The S26a has a spring on the rear cap and a “cylinder” on the driver’s side. The S21a has a spring on both sides.
Does anyone have any idea how I can save the S26a? Is it possible to buy a driver with a spring?
Thanks in advance
What led the S26 is, is it the xhp70.2/3 if thats the case; you can purchase the 6v5a 17mm driver + additional retaining ring for the 17 to 22mm converter.
Cheers 
Hello LAMPUSAKU,
Yes, it’s exactly that, the XHP70.3 HI R70. Thank you for the quick reply and the good news.
I have to wait that convoy comes back from the holidays and after I will order it.
Thanks
Spring both ends is best option.
Alternatively you could use a stronger spring in the tail, or use a longer cell, or wrap a ring of tape around the cell so the friction prevents it moving as easily.
Hey, I had a very similar problem with my M3-C, and ended up soldering on a tiny spring on the end of the brass post.
This one I think. It’s tiny and just the right size. Really easy soldering, just don’t accidentally desolder the post itself that’s a bit trickier.
Hello gravelmonkey and EthanR,
Thank you for the ideas. I think I will wrap something around the battery yes and add a spring to the post.
I live in Europe, so I need to find another seller other than Mountain Electronics, but that should be easy. Maybe I won’t have to buy another driver in the end, we’ll see how it goes.
I added an additional small spring inside of the spring on the tail cap. You don’t want too much additional pressure so you do not damage the cell or driver, but it works fine for me. I think an additional spring on the post might be better, but I did not have anything suitable and was afraid to heat the post too much and have it detach…FWIW. Just threading the little spring in and adding a bit of solder did the trick.
Thank you Mandrake50 for your feedback.
While looking for a spring, I found this kind of connectors, pogo pin:
It’s similar to the post connector in the S26a, but these pogo pin have a spring. However I know nothing about this, do you think I could replace the post by this ?
If I remember correctly, some (all?) modern zebra lights use POGO pin connectors.
Depending on your soldering ability, it might be a challenge, it’s a large metallic component so might suck up a lot of heat?
I’m a fan of the additional tailcap spring in the back of the light; you have to take care at the head of the light- the positive cell contact and the body tube (bringing the negative end of the cell contact to the driver) are in close proximity, which leads to risk of shorting the cell if your spring becomes detached etc.
I have no experience with those . But it looks like it may work, if you can size it right… and as @gravelmonkey mentions, can get it installed without screwing something up.
Make sure the base of the pogo pin not hitting any components protruding around the brasspost.
I prefer the 'add spring to the post, small amount should sufficient, if you worry about the overpressure, simply lessen the length of the tailside spring
Cheers
Looking online the springs + shipping cost too much. In comparison I can order the driver with the spring from Convoy and I can also buy a spring there (in case I still need to add it to the tail cap).
Anyway, if I come across a physical shop that sells that kind of stuff, I buy it, otherwise I stick to the first plan.
Thank you everyone for the help
Couldnt agree more!
The bright side , you have yourself a good reason for another host to slap in the old driver 
yes, I will have to see what are my options
Hello again,
Just to give some feedback. The problem has been reduced but hasn’t gone away. When the back of the flashlight hits the handlebars, it changes mode:
However, if I move the torch here, there is no problem:
I will keep this solution for now. I have an S21E and when I tap the back of the flashlight this problem never happens. So maybe an M26D would work well here.
M26D uses a brass post for the driver and would have the same problem. You want springs on both ends for this application.
Hi EthanR,
Yes, but I could replace the driver with a spring as I did on the S26. The behaviour of the S26 and M26D is different, the M26D works like the S21E, right? So maybe it won’t change modes or anything and work properly. At least the S21E works quite smoothly.
Not to hijack the thread but I wanted to ad I used a C8 I got from Mountain Electronics as my primary light when I was a bike commuter for several years and it always worked great. I started with a Road Toad or whatever they called it and gradually worked my way up to the C8 and the C8 was my favorite. My neighbors would say I looked like a motorcycle as they saw me approach. I did have problems with mode skip on a 501B with Ultrafire 18650s though and wrapping them in tape worked, but not as good as replacing the cells with some Panasonics.
