I have a Convoy S21E with LHP531 and Anduril 1. I got this driver to push the LED hard with FET driver and have anduril. The combines incredibly bright and throwy.
However the triangle buckle tail spring gets incredibly hot and I desperately need to reduce resistance. FYI the head spring doesn’t get nearly as hot.
The problem is where to attach a bypass wire? I can put a nice solder blob and attach a wire to the end of the spring where it contacts the battery. Usually the other end would go to a solder pad at the base of the spring. But there is no pad. There is just the bare aluminum tail cap. I don’t think tin/lead solder will work.
Looking for suggestions.
Also as I look at this picture I see I need to clean up the contact surfaces with Qtip and alcohol.
The other end can just go to some point on the triangular base of the spring. Or better yet:
Be sure to solder to inner or back side of the brass ring, not the front face with the 2 indentations–a typical-sized solder blob there would make the tailcap impossible to fully screw on.
I don’t know what material the existing spring is–it looks like steel to me. In that case, soldering to it could be the main difficulty. Brass, on the other hand, is much easier to solder to.
Just solder to the bottom of the spring, where it sits under the retaining ring is the best place. That will easily do the job, don’t worry, the contact will be good enough.
Put a drop of solder to the end of the lead and hammer it flat. Clean the lead and the underside of the spring thouroughly. Shove the lead under the spring. When putting in the retaining ring, make sure the lead sits under the retaining ring. Then fasten the retaining ring. Now the lead is not bonded, but fixated. Should work.
The spring is already making plenty of contact with the bottom of the retaining ring and the aluminum.
That is if the retaining ring is tight. ??
Check that first.
How are you determining that the spring is getting hot?
I never liked that spring design so after a short burst of turbo (maybe 10 seconds) I opened the tail and touched the spring. It was extremely hot (non scientific I know).
I think I will take the suggestion to make bypass to the base of the spring, at the mid point.
Neither do I. I always thought it is just a money saving design to get rid of the PCB. A cheaper , but inferior workaround. I think the resistance can be influenced by the AL oxidizing over time. In which case bypassing from the top of the spring to the bottom might not be as effective.
I kind of like the idea of fitting a smaller BeCU spring inside of the existing spring. As long as the tension is not so much as to damage the cell.
How is it done. I can’t really tell from the photo. I see the tab on the bottom soldered to the spring. I see the button on the top of the spring. But not how they are connected.
It looks great, but the linkage is a mystery. The big problem I have had with some of my bypasses is the wire coming loose over time. Not the solder but the wire breaking with repeated flexing.
Yes I always try to make a bit of a coil with the connecting wire. 1 to 2 turns. But 22 AWG insulated wire still doesn’t flex that well…putting stress on the soldered ends. This gives the connection a limited number of battery changes before it fails. Which is why I am interested in what @1stein does for that connection.
It looks like the attachment of wire to spring is not just soldering, but perhaps the wire strands were wrapped around the spring prior to soldering, for additional mechanical support.
I haven’t had a wire bypass fail by stress on the soldered ends, the main issue I encountered was the wire wicking up too much solder and becoming stiff. Some additional length/tolerance should help fix this.
Since it was in the tail cap, I would bypass with a ‘stripped’ 20 awg round the outside of the spring coil, and if you can’t solder the alu ; simply clamp the wire between the bottom of the spring and the shelf, then solder the part that touches the retaining ring.
