That looks like a safety hazard…
Thank you for your opinion. I’ll consider it if/when I remake my enclosure
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may be a little bit hazardous… but more than that it is likely to have additional failures and internal disconnections that disable your board. Why not spend the time to get it closer to perfect? Those braided lengths of wire are not long enough, presumably from your photo you once again are asking metal to stay intact after bending it 180 degrees and subjected to the same stress that broke the nickel tabs.
Focus on isolation of individual pack segments, longer lengths of braided wire with the sheath still intact.
People will overstate the safety risks often IMO but they shouldn’t be ignored completely, People have lost their homes to bad battery assembly. Like I said more likely it will be just disappointing or embarrassing if you don’t take time to get it right.
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What are you using to prevent shorts between the top and bottom rows? Fish paper?
Also, one of the main reasons I didn’t do this configuration in the beginning was that this has 10 junctions of this troublesome head-to-toe arrangement that I tried to use the U bends to resolve. What are you doing here for those joints that I can use to improve mine?
I will only be having one row as it single stack, but yes fish paper would be put between the rows. I will also be having fish paper separating each p group.
In a single stack design I am going to lay a strip of copper on top of the cells at each end and then connect that to the nickel welded to each end of the cell with 14awg wire. This way I can just run 1 12awg wire between each series connection on top of the cells.
You could also rotate the cells 90 degrees so that you can then do one long nickel/wire connecting the p groups
Do you have links to examples, guides or general photos of how others are accomplishing this?
@thisguyhere sells pcb boards that make it much easier and tidier. If you also have a look through this thread you might get some ideas
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some recent photos of batteries being built, see if you find any of it useful
Yeah, I remember looking back briefly at that thread you linked to early into my build and at the time remember seeing things like this:
And thinking 'oh, the head-to-toe connections just look like some bend nickel, easy-peasy.
From the sounds of it, you’re suggesting to redo the head-to-toe connections to be more like this?:
With the bend right angle nickel strips over the edge of the batteries, with fishpaper insulating behind it
Both of these photos are from that thread.
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So I really like the video in that album of the pack once there’s two rows of batteries, but I just don’t see how those two rows are connected in series. What are you using to connect it?
but to answer your question, the two half are connect here using the same copper strand you see for the other series connections:
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THIS IS NOT A FINAL SOLDER. Just an example of what I’m thinking about to give an example. I’m taking the communities advice and remaking my battery connections. I recently bought some better flat braid wire and more nickel strips. This photo’s an example of the idea I’m seeing, with the only-right-angle bends and wire on top.
Obviously this pic has some pretty cold joints but the concern I’m having is that the nickel strips are still going to break between the terminal and connection to braided cable.
In addition, I’m noticing the braided cable is pretty stiff, since the solder gets so quickly sucked up along the fine threads through capillary action.
Any advice on how to tackle these concerns?
Thanks
Pre-tinning the nickel will help, the faster you solder the less it will wick.
You should also have a horizontal nickel strip going sideways across the P group, it will help keep the strip stable and prevent damage.
Short lengths of copper wire will do that, I don’t think you can prevent it.
Here’s one method to deal with it
And generally scroll through this thread and look at photos
examples like this Please review my battery pack so I don't make a 🔥 - #13 by RHill051 - ESK8 Electronics - Electric Skateboard Builders Forum | Learn How to Build your own E-board the long bent wires on the left, will help with wicking of solder.
Another example more similar to yours (my post) Please review my battery pack so I don't make a 🔥 - #163 by deucesdown - ESK8 Electronics - Electric Skateboard Builders Forum | Learn How to Build your own E-board
btw use fish paper not electrical tape. e-tape won’t stand up to abrasion.
In my opinion you just need to secure the battery better. The battery shouldn’t really be under that “accordion” style stress that caused those pieces to break, and making stronger connections isn’t really the answer. I’m not saying you don’t need strong connections, I’m just saying that your connections shouldn’t be the only thing holding the battery together.
I would just re-weld it just like you did(assuming these are spot welded?) and wrap the shrink wrap better/tighter this time and also add some support. You can use some strong tape as support for the battery before you shrink wrap it to give it more rigidity. Use clear shrink wrap.
Then you need to make sure there is padding around the battery so these battery destroying vibrations don’t ruin anything else. Adhesive backed felt tape works really well.
Finally, I’m not sure how the battery is secured, but it needs to be supported better to reduce stress. Strong connections, structural support(not the connections), thick/thorough insulation, and sufficient padding are paramount to building a safe and reliable battery.
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+1 I usually cut a sheet of abs slightly larger than the pack, tape it to the pack, then shrink. Even for a flex pack the abs is flexible, but will mostly keep things from moving around.
Where are you able to find the ultra wide nickel strips? The only way I’ve found it is in giant reams of 50+ meters
By adding strong tape, do you mean just SUPER tightly wrap the entire pack in something like packing tape before shrink wrapping it?
It’s very tedious to find on aliexpress…
Filament strapping tape
https://www.amazon.com/Scotch-Filament-Tape-Clear-Pack/dp/B00548R6AU
But really any way you can think of to stabilize.
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