10s6p 18650 No-weld, No-solder, No-screw Bamboo GTX pack

I've been slowly working on this for more than a year, as my 3-year old original battery gets worse and worse (18mi AT range when I got it 1 year old, now down to about 12mi.)

The design criteria were simple: Fit in the original battery cover, (with a thick spacer,) allow some flex in the longitudinal axis, avoid use of spot welding / soldering by compressing cells against (tinned) copper braid thick/wide enough to handle 80A. Avoid the use of expensive/heavy threaded rod for compression. Design parts to self-align when assembled.

Overall length of the pack is the length of the cells themselves = 65*5 = 325mm + 2mm for each mid plate + 8mm for each end plate = 325 + 8 + 8 + 8 = 349mm + whatever wire pokes out. The cells are on 18.5mm centers + 1.75mm on each side = 18.5*6+3.5 = 114.5mm. Height is that of 2 cells stacked = 18.5*2=39mm. 353x114.5x39 (Alowing 2mm of wire protrusion at each end.

Both the end caps, and mid-plates are printed as two pieces. When assembled, they self-align in 2 axes around the copper braid and copper discs that form the parallel straps + battery contacts. Only the discs are exposed to the end of each cell, the braid itself being protected from contact with the outer can by a 0.25mm layer of plastic, (Taulman Alloy 910 in this case, which is a rigid Nylon 3D printing alloy.)

Cell connections are via 3/8in (9.5mm) diameter copper discs, which I am punching out of "Oxygen-free" sheet with a large hand punch. The pip left at the center from punching will be oriented toward the braid, leaving the largely flat surface against the 10mm diameter exposed pad on each cell. These are soldered to the braid from behind. The braid is 7x0.7mm tinned copper, doubled, which should handle 80-90A. The end caps have the copper discs on only 1 side, mid plates on both sides.

Each 5s stack is compressed by lacing with .041 = 1.0mm dia 304 stainless steel wire, twisted to tighten. Additional longitudinal tightening can be done by forcing a wedge under the crossed wires on either end cap. The half-cylindrical pocket on each end cap is for shims and/or neatly containing the twisted lacing wire ends. I've included the oval bores on the end caps to allow the wires to be secured with a zip tie, (not shown.)

The complete pack is printed in 24 total pieces, 8-up at a time, takes roughly 18 hours total to print, consumes about 100cc of filament.

I'll need about 10m of wire to lace it up, a bit more than 5ft of 1/4in tinned copper braid, and 120 of those 3/8in copper discs.
(I found them sold in a couple places online, but it was going to cost around $30 on my doorstep, vs $90 for a sweet punch + dies... I'll be making packs for other projects so...)

Comments? Questions?

More as it comes together.

Eric

 

Okay, there were more criteria This is supposed to be an easy DIY pack for anybody with access to a decent soldering iron and 3D printer, (even a small/basic one without a heated bed.) The only soldering is tacking each copper disc to a strip of braid, held in one of the 3D printed plates used as a jig, and soldering balancing, power and series wires to the ends of paired braid strips... NO soldering or welding is done on the cells themselves. Optionally, with great care, the pack can be assembled with no soldering at all, relying upon compression in the pack to compress each I/O and balance wire between the two paired strips of braid, and each battery-disc-braid-braid-disc-battery sandwich.

No un-insulated wire is left exposed with this pack, so unless for aesthetics, armor, padding, or securing wires, I don't see the need for a wrap of any kind.

 

I kinda don't like much the idea of not have the connection properly soldered or with spot welding but I think you doing a great job there.
How big will be the spacer?

My GTX battery is sagging quite bad and soon It will need a new battery so I'm looking into options.

 

Well, after partially assembling half of this pack, I'm convinced that in this form (laced with ss wires) it is MORE difficult to assemble than welding or soldering. So difficult that any benefit of easy future disassembly is moot.

Since I've already got the 60 cells, I'll finish, but for others who are not gluttons for punishment, I suggest staying qith the easier to make 10s4p "butterfly" pack design (with a spacer of course.)

To tide me over, I built an 8ah 10s1p SPIM08HP pack in an Apache 1800 case I strap to the board. It charges separately, has its own 35A BMS, connects in parallel to the internal battery via a Neutrik Speakon NL4 cable (2x 14ga pos, 2x14ga neg.) I just set my distance record, 18.6mi, most of qhich was at 19mph Prior to running this booster pack, I was lucky to make it 6mi before hitting eco mode.

More as the "braces face" pack develops.

 

This is absolutely epic! Any pictures of the printed pack? Have you tried it out yet in the wild?