EBike Battery Rebuild for a tranzx akku

Nov 16

This Instructable is not meant to teach you How To but rather Why Not To rebuild your own eBike tranzx akku. Having just completed a months-long rebuild of mine, I have a list of painful lessons to share, all of which add up to this one piece of advice: if you can purchase a new lithium battery pack for your eBike, do so. There's a lot going on inside your eBike pack, welding batteries is a finicky business that requires specialized equipment that's not good for much else, the final product is unlikely to be really reliable or to last a very long time, the chance of fire or explosion is real, and there are probably other projects from which you can learn a good deal more.

Step 1: So What Does Rebuilding an EBike Battery Entail?

Really, you're still reading? OK, let's get into it.

The big, heavy brick that powers your eBike is a set of battery packs wired serially with a controller that governs how each set is charged and monitors the battery's performance when charging and being discharged. Each battery pack is itself made up of individual cells (which is what most people think of as a "battery," AA, AAA, what have you). To rebuild such a pack the main steps are as follows:

Open the battery casing (may be surprisingly difficult: they are usually sealed against water, so you will probably destroy the waterproofing and the warranty alike upon doing so).
Disconnect the various leads, some soldered, some glued, that monitor electrical flow and temperature, making sure to keep good track of what goes where. Eliminate silicone plugs or other material used to hold the battery packs or individual cells in place. Strip out any tape or other additional material you find inside, again, taking note of every piece, its location, and what's under it. Details count here!
Remove the individual packs, making very careful sketches of the sheet metal formations used to define each of these packs, top and bottom. Details count here too!
Strip the connecting metal from some of the individual cells in each pack; you will need these "dead" cells to practice on as you prepare to assemble a new battery pack (indeed, you may need all of the dead cells for this purpose) and will probably want to practice spot welding on some of the stripped metal.
Source your new materials: new cells plus extras, and at least twice as much sheet metal as you think you will need to recreate the sheet metal formations mentioned above. (Note that you may wish to use a different thickness of sheet metal than that used in the original pack but probably don't want to use a different typeof metal; typically, you are buying a highly conductive nickel alloy.)
Beg, borrow, or buy a spot welder. Do not beg, borrow, or buy the one shown above or any other that is intended for "hobbyists": you will probably need to make several hundred individual welds in order to build your pack, and will require a professional grade piece of equipment to do so. (So at least there's that: by the end of this you will no longer be a hobbyist spot welder.)
Practice a lot with your new spot welder, your old metal, your new metal, and your old, dead batteries; figure out how to deal with edge cases, such as welds at the end of a strip.
Recreate the sheet metal formations using your new metal and a pair of shears or, more ideal, a laser cutter.
Weld the new batteries to the new sheet metal formations at the right points and with the correct orientation in order to create your new battery packs.
Place the new packs in their correct positions. Attach each wire and lead in the correct spot as indicated in your careful notes, using specialist glue or soldering as appropriate.
Kit, glue, tape, and otherwise physically secure the battery according to your careful notes.
Return completed battery to its original housing and test the new battery by charging it as per usual.
Assuming the battery charges correctly, start using your bike and charging normally.
Assuming nothing goes wrong, reseal the battery in its housing before the first rains.
Don't forget to dispose of the old cells responsibly.

Be sure to take lots of pictures and movies for the sake of reference and to record suitable measurements of voltage throughout as well. or go to: https://kwsseuren.de/