AXS Battery Contact Repair Guide

Summary

If your battery contacts on your AXS derailleur stop working or get stuck down, you might be able to get them working again using the tips on this other page. If not, we documented a DIY repair below.

This repair replaces SRAM AXS battery contacts with alternate pins and an alternate 3D printed plate.

Madrone no longer offers this service because it is too difficult and time consuming to offer as a professional service. However, because AXS battery contact issues are common and there are many units out there, we are publishing a process here as a service to the cycling community.

This repair is best suited for people who have soldering and 3D printing experience, and access to all of the tools or supplies.

The contacts and 3D printed plate have been changed to make the repair process easier, but it is still a challenge for anyone without previous soldering and 3D printing experience.

This repair is not “stock” and not approved by SRAM. However, if done carefully it works great! And if your derailleur is otherwise e-waste, it may be worth repairing.

Good luck!

Tools

Safety glasses.
Well-ventilated and well-lit work area.
Brass mesh for soldering tip cleaning.
Soldering iron with clean / small / pointy solder tip.
Wire cutter / stripper for very small wire. A sharp, precise one works best.
“Helping Hand” soldering fixture.
Heat gun with small nozzle.
3D printer (to make a new battery contact plate).
Tweezers
Small needle nose pliers
T5 torx driver

Supplies

Soldering tip tinner.
Fine flux core solder, such as 0.5mm, with no lead.
28 gauge (0.08mm^2) wire, multi-strand, flexible, insulated.
Small diameter (e.g. 2mm ID) thin wall flexible heat shrink. It should just large enough to fit over the wire and back of the battery contact which is 1.7mm. It should be thin and flexible when shrunk on the wires and contacts.
Spring loaded battery contact pins (Mill Max 0933-1-15-20-75-14-11-0). For example, you can purchase them at sources like Digikey and Mouser.
3D printing material (e.g. PLA) to make a new battery contact plate.
CA (cyanoacrylate) adhesive (thin viscosity, good quality hobby grade recommended). For example, you can get this on Amazon.

Tips

This can be a difficult repair. Be patient and take your time with each step.
Read through all of the steps before beginning. A successful repair involves doing the steps in order.
If you are new to soldering, we recommend to:
1. Watch some YouTube videos on the basics of soldering.
2. Keep your tip clean and tinned.
3. Make sure you have all the soldering tools and supplies listed above.
4. Practice soldering techniques on spare small wire before you work on your costly AXS derailleur.

Steps

(photos below)

3D print a few new plastic plates from this step file. The step file will need to be imported to a 3D printing software to be prepared for printing based on your desired settings and material. For example, you can use a common FDM 3D printer (such as Prusa or a similar one) and standard PLA material. The part is small and requires good tolerances and surface finish, so it is sensitive to printer calibration and print settings so I've dialed them in to get good results on this part.
Check the 2 hole sizes for the battery contacts by sliding a battery contact into each one from the back side. It should stop on the lip of the contact. It should not be loose. It should require a small amount of force to slide in with friction. The friction helps keep the pins aligned, held secure, and prevents CA glue from getting into them in later steps.
1. If they fit too loose, adjust the hole sizes, and re-print them.
2. If they fit too tight, you can adjust the hole sizes and re-print them, or gently ream the 3D printed holes for the pogo pins (from the inside how they will be installed) using the T5 driver until they properly. Don’t ream too much or the holes will be too loose.
Remove the small torx screws with a T5 driver and take care not to lose them. If they get lost you can replace them with screws that are M1.6 thread, 4mm long, with low heads, and T5 drive.
Remove the plate by pinching one of the pins with a pliers. Do not pull on the seal or it will damage it.
Do not pull on the wires or cut them!
Write down which wire goes to + and which to - and the orientation to the battery. The battery (not derailleur) has small + and - markings on it.
Remove the black plastic plate that the pogo pins pass through.
Do not cut the wires!
Un-solder the wires from the 2 existing pins on the small green board. This will keep them stripped and tinned nicely for the soldering step. You will not need the old pins or small green board.
Ensure the 2 wires are tinned, and no not have broken or missing strands. They should also be straight, with about 4mm of tinned wire exposed.
Remove the rubber seal that the wires pass through.
Clean the rubber seal and set it aside for later.
Clamp each battery contact using the helping hands fixture, and fill each solder cup with solder (but don't over fill). Remove any excess solder.
Cut two lengths of new wire a few inches long. They will be trimmed to length later.
Strip one end of each wire about 4mm.
Tin each end of wire.
Clamp the battery contacts in the helping hand fixture, and solder the wires into the solder cups. Remove any excess solder.
Slide about 8mm or heatshrink over the wires so it overlaps with the back of the battery contact.
Shrink the heat shrink with a heat gun.
Press the battery contacts (with wire and heatshrink installed) into the back of the battery contact plate until the lip stops it. The contacts should protrude through the front equally, and be perpendicular to the plate. The contacts should stay in place easily, with friction.
Hold the plate horizontally with the helping hand fixture.
Drip a small amount of CA glue (thin viscosity, high quality) onto a disposable object such as the bottom of a can, or a plastic container lid.
Using a small/thin disposable wire, dip it into the CA glue, and then touch it to the back of the battery contacts where there is a circular rim on the 3D printed plate. The small wire will help control the application, the thin CA will wick into the rim and bond the contact to the plate, and the rim will contain the adhesive.
Build up an adhesive joint around the full circumference of each contact. Make sure the rim is full, but not over-flowing with CA adhesive.
Do not allow the CA glue to get on the front side of the battery contacts or they will not work.
Let the adhesive cure fully, then repeat the process until you are confident that the joint is strong.
After the adhesive has fully cured, put the rubber seal back over the wires and over the 3D printed plate. You may need to press the seal down around the heatshrink to get it fully seated, but it will stretch.
Trim the lengths of the wires (the ones connected to the new contacts) to about ~25mm (1”). Shorter will fit better inside the servo, but longer will be easier to work with.
Strip each wire about 5mm.
Tin each wire.
Now the battery contact and plate sub-assembly is done, and you are ready to make wire-to-wire solder joints with the wires on the servo.
Cut short lengths of heat shrink, perhaps ~8mm long. It should not be too long, while still covering up the entire solder joint and overlap to the insulation on each side. If it is too long, it will be difficult to get back inside the servo, and add strain to other areas of the wire inside the servo.
Slide the heatshrink over the wires and move it as far from the soon-to-be-made solder joint as possible so it does not accidentally shrink while soldering.
Gently bend the 4 wire ends into hooks. Take care not to damage the wire or insulation.
Hook the the new wires to the old wires, and bend them into tight hooked joints. Make sure they are as compact as possible (for later installation to the servo).
Solder the twisted wires together.
After the solder cools completely, slide the heatshink pieces over the joints and shrink them so they overlap the joints completely, and overlaps the wire insulation on each side. You can use a tweezers to hold the heatshrink pieces in the correction positions while they are shrinking together.
Now the soldering is done and you are ready to re-assemble.
Double check the + and – orientation of the wires, and hold the battery against the contacts to verify that it will power the derailleur on and shift.
Carefully slide the wires into the servo, while taking care not to stress any wires. You want the wires to slide in the "down" direction. This is the direction pointing to the ground when the derailleur is on the bike.
Seat the seal and 3D printed plate into position.
Re-install the small torx screws with a T5 driver. Do not over torque them. We do not have torque specs, just be gentle.
Double check the function by installing the battery and clicking the AXS button on the derailleur (single or double clicks depending on the shift direction).
Repair complete!