Why multistrand not sheet

Everyone uses multistrand for a lot of good reasons but tell me if u have a good explanation for why a foil of point two millimeters would be more likely to break than multistrand fibers of the same diameter if both were only bent in the one basic direction suited to the foil. Just comparing their likelihood to break with that repeated flex why would one be better than the other. Really trying to figure if a twenty four cell long pcb with flexing would break the traces.

Because they can move in any direction. Sheet is only flexible in one direction.

If this is about Kickstarter, my suggestion would be not to investigate a new battery pack technology. Just sell with professionally built packs. Or, better, even without it. Otherwise it’s going to be a huge time stink and resource sink and the Kickstarter won’t happen. But I am guessing I am the 100th person telling you this. :stuck_out_tongue:

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Just curious. Have a pcb design for twenty four cells n half the people who make them think be fine and other think will break. It’s a small investment to try. But for Kickstarter will use something tried n true. Can’t find my photo of that but here’s the basic four cell pcb. Blasto made pretty much the same thing and ran it. Don’t know how his is doing.

Trying to do everything inhouse IMO was the downfall of those damn raptors.

I mean Jason wanted to make his own deck, own esc, own motors, own wheels, own enclosures, own battery. everything inhouse and look at the delays.

Its business 101 that you focus on your your core strength and my man, thats your deck and your hubs. Dont even try to do anything else inhouse. You will be stuck for months with no end in sight. GO for tried and true like you sid.

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I use 0.15mm nickel now.

assuming the nose of the deck is north and the bottom is facing you, and the cells are in an east-west oriantation:

you don’t want any sort of series weld with anything other than high stand count wire in the north and south direction. Flex will wear it until it breaks, even on boards with no flex. this was basically my entire problem with batteries during 2016.

foil or nickel strip with the hump of the bend pointed toward the deck is the way to go on east-west series connection welds. North and south, wire only.

The reason for this is that the deck not only flexes, but twists. Again, even decks with “no flex.” The twist isn’t enough to really agitate the welds on the east-west series connections as long as the bend-hump is pointed toward the deck. If its flipped over, eventually welds will break. Not catastophically, but the bms will simply stop charging correctly.

but the flex and twist is definitely enough to mangle series welds in the north and south direction over time.

a lot of people have come up with a lot of solutions for this. PCBs are popular but overkill in my opinion. You can build a supremely flexible pack with series wires and foam padding between the P groups, been doing this on the 10S4Ps i do in the evolves forever.

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I’m still waiting for parts to show n then will do Kickstarter and getting someone else to do batteries but That’s a lot of building with multi strand and the nickel strip. There’s some flexible pcb maker I’m waiting to hear back from about what are the possibilities but if the copper on a regular fiberglass board is true pure copper it should have many flex cycles possible before work hardening n cracking. And as I am wondering and asking why would point two mm sheet be more likely to break than point two mm strand. If the strands break in the wire of course not a problem n many strands in there and touching but don’t think that even happens. An example of a place. https://get.rushpcb.com/flex-pcb-lp/?gclid=Cj0KCQjw_r3nBRDxARIsAJljleHEpx9-mhu6POhlGhy2rz6GVhdRe1RrE-I1UgtusfInNITX-igbN2UaAoUbEALw_wcB Could be easier to make and a safer battery. Maybe even cheaper but prob not.

If the sheet is flexing in the flat direction, it should have the same fatigue cycle as wire. Evolve did exactly this on their new GTR battery fyi.

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Aha. I couldn’t see what they were doing exactly. I got a twenty four cell pcb designed and price quotes. Six s four p. If anyone wants to order some we can bring the price down. If we get two hundred it’s like five bucks each.

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You’re going away from compression? I’m having this thought.

A good solderless pack setup would allow you to sell the board without cells, with easy mostly foolproof assembly by the user. This would get you out of shipping cells/packs, and if sold as a “kit” could possibly shield you from liability for broken stuff or fire. kweld spot welder takes this approach.

The pcb with balance wires in your photo above, the thing that worries me is the soldering pads are too close to the edge of the board, so it’s hard to mechanically secure the balance wires. For tests I sanded back the solder mask so I can solder the leads more toward the center, and glue the wires down. Also ideally the balance wire pads should be spaced for commonly available ribbon wire – I stalled out researching this part. Oh and it’s a real pain to strip and solder so many connections. The other concern is current sharing, as the power bus part of the pcb is asymmetric.

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Above photo in the thread is of the common already made just four cell pcb and the plan is to get this long version made. Compression battery would be ideal in the ways you say but my rubber band version wasn’t ideal and would need be altered to have bigger contacts and subsequently the deck hole enlarged too. image This last pic is the evolve flexible battery

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the difference is that the “foil plane” is parrallel to the deck plane and not perpendicular. That’s the only reason it works for evolve. Also, i don’t think they’re using fiberglass in that flexy pcb. Its more likely a some kind of copper/plastic laminate like a super heavy ribbon.

if the foil plane is kept parallel to the deck and not perpendicular it should be fine. But every china pack that’s ever broken, including the space cells back when and the 12S3P i just put on a shelf last month use nickel strips on the series welds north and south and the foil plane is perpendicular to the deck plane, and 100% those packs fail on a skateboard before the cells have been used up.

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U have any pics of the evolve details. I can get the simple fiberglass pcbs made and worth a shot but there’s also some places that make what they call flexible circuits and really it seems nothing special and just copper wire or sheeting contained within a soft Pu or stuff like that and waiting on quotes from them. But as we seem to be agreeing the simple glass pcb may be fine and think will get those.

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pretty sure you nailed it on the head. I can’t find it now but somewhrre is a half second video clip online of an evolve employee flapping a pack up and down in his hands to demonstrate flexibility and its a pretty serious flapping.

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For you to do it properly though will take time and money. If you don’t do this prior to your kickstarter it will push your R&D even further out. It probably won’t be perfect the first time around either.

You’ll want a custom flexible PCB which replaces all wires BMS and the series connection. It looked like their BMS was also connected to this PCB.

They PCB riveted custom plastic spacer cells in 4P modules onto the flexible PCB.

Then they just have 10s4p with 10 modules that they solder pos/neg to the PCB and rivet the spacer block to the flexible pcb. So its probably 2-4 rivets and the nickel tab on the spacer cell.

It’s a smart idea but this will take you too much time IMO.

At least that’s what I think they did.

I’d stick to 10awg and maybe 18650 pcb modules. That way people can actually repair and fix it themselves.

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Maybe even go with NESE modules. And from the kick starter money you can make actual injected moulded parts for durability. You can see them without battery and not worrying about shipping laws involving the cells.

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I’m just going to sell w the welded fourpacks connected w multistrand. Nothing experimental. nese seem experimental still. or at least looking at the tiny bit of compression foam in them im skeptical. but I guess they’ve shown well. maybe do that.

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I wasn’t paying attention before: what’s the legality on selling and shipping batteries, and what’s the reality?

I got these today! (post pics in a min).

I don’t know who designed these ones but there’s some other designs around and there’s a link to get them made somewhere but I got them through thatguythere on the other forum.

anyone have a link to a good tab? these are ideal in having a horizontal “H” shape so don’t have to weld one yourself. I show it at .16mm thick. its only 7mm wide, why not go as wide as almost the whole cell? the downside with these they don’t have equal legs for all the paralleled cells (pretty worth while) and also the slots in the nickel aren’t evenly matched to each cell. maybe that’s nitpicking and maybe that weld connection is more important than the legs. I could spend 10 hours looking for the ideal strip. maybe custom is cheap and hope so.

this pcb shape seems good with it recessed behind the four welded cells, that and the traces recessed behind the edge of the board and its hard to short while building or on the board.
the board itself is 1.6mm. the trace is only 15mm wide and one sided and even if 2 ounce copper surely isn’t up to a 60 amps continuous rating. its no 12awg. I barely know much about this stuff but will be getting 30mm wide traces on both sides with an integrated shield on the bottom and that is rated to 60amps continuous, according to someone. bigger better regardless. Maybe not a big deal but was told soldering onto these tabs is not ideal and I can imagine youre pulling solder from all over when doing it and thinning it in places further increasing resistance. I look forward to feeling the heat off these after doing stout rides and seeing if its all fine.

the single pcb design will be thinner fiberglass than this 1.6. for flex. the cells glued to the board would give the rigidity so no stress on any nickel.

the cost isn’t much for normal people and when I get a quote that looks good, for this pcb or maybe something from the flex circuit people, i’ll hit you up here to see if you would get a pair to test. the cost difference between 20 and 200 is a lot but if this were to get down to maybe even 10$ each that seems well worth it. If it shows well. the price so far 200 is well under that.

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My thinking is, rather than the railroad tracks, use double wide nickel, and fold it over. Don’t really need the pcb this way, and the current handling is better. The only downside is the slots to help spot welding are missing, but that’s really not a big deal.

Here’s a photo that shows it. I used .20mm x 25mm strip

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looking for prices on the big pcb still. big difference between 20 and 200

looking below it looks like the pcbs I got with 2oz copper and 15mm trace (think that’s what they are unless something hidden inside)…theyre equivalent resistance of about a 17awg wire! I’ll definitely be going long on the multistrand connectors.

http://skottanselektronik.com/
https://www.cirris.com/learning-center/calculators/133-wire-resistance-calculator-table
https://www.pcbuniverse.com/pcbu-tech-tips.php?a=4
https://www.bing.com/search?q=10+feet+converted+to+mm&form=EDGTCT&qs=UC&cvid=dbc12aa73c284c8b87bfc7826441906c&refig=d46137562ea6466ac66eb3c8c62a6ff7&cc=US&setlang=en-US&elv=AXK1c4IvZoNqPoPnS!QRLOPz4e7yH7q1FEejlLQi7JGdKQOqyJhp1xLEWZFqliAr018RXaRp%21NqNmX8UUKg2yDBBCZD2U5BuNzubdwrUWV&PC=HCTS

what I would get would be dual sided (with mask on one side) 30mm each side, 2oz, and that is a bit better than 12 awg.

will use fat nickel like you show .2mm x 25 looks good.

If you use this, what’s the function of the pcb? Electrically you’re adding copper wire to carry the current, right? Flat copper braid on top? If that’s the case the PCB isn’t adding anything electrically.

Is it just for flex structure? I’m simplifying but you can hotglue the groups to a sheet of ABS instead.

I want to say, I’m not advocating you do this or that. Just curious what your thoughts are and trying to improve my understanding.