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Wiring Plans For Modular System
#11
That's a whole lot of space and plastic to house just 12 cells.  There must be a more efficient and compact design?
AWG 10 for just 12 cells is overkill especially if your absolute peak draw is 1A/cell.
How is the sled/spacer put together?  Glue? Screw? Snap-on?
Do you have a shopping link for the leaf springs?

I've had problems with zip ties allowing the straight cable to slide length wise, no matter how tight I made it.  Simple solution: bend the end into a "key" hole.
Modular PowerShelf using 3D printed packs.  30kWh and growing.
https://secondlifestorage.com/t-AJW22-s-...PowerShelf
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#12
(08-26-2019, 01:05 AM)ajw22 Wrote: That's a whole lot of space and plastic to house just 12 cells.  There must be a more efficient and compact design?
AWG 10 for just 12 cells is overkill especially if your absolute peak draw is 1A/cell.
How is the sled/spacer put together?  Glue? Screw? Snap-on?
Do you have a shopping link for the leaf springs?

I've had problems with zip ties allowing the straight cable to slide length wise, no matter how tight I made it.  Simple solution: bend the end into a "key" hole.

That is a lot of space and plastic.  For me that was the trade-off to allow simple insertion, removal, and inspection of each cell individually.  I have laid this all out and can fit 144 of these modules into the server rack.  I will alternately build a row of "service" mounts on my workbench.  That way I can mount a module for pre-balancing and testing/troubleshooting.   There may be a tighter design.  But it would have to involve the spacers because the cell sleds cannot get any smaller.

My first iteration was a little tighter in a square format.  But I found that I didn't really have enough room for the fuses on the positive side (working my fat fingers in such a small space)  I widened out the bottom positive end to give me a little extra room.  That also eased my paranoia of a cell working its way out of the module by tilting them backwards on an 80 degree angle.

The modules are 123mm Long (4.84") X 82mm Tall (3.23") X 91mm Wide (3.58")   So what seems gigantic in the pictures is really not that large.


I am going to follow your advice on the 10 gauge wire.  You were absolute right that it is difficult to work with.  It is tough to strip and difficult to bend in a tight radius.  It is also a pain in the butt to try to cram into an XT-60 connector.  Ill retry this with 12 gauge wire.  I do not want to go too small because the wire comes in direct contact with the spacer.  The material is PETG, so more heat resistant than PLA.  But I do not want to risk a hot wire warping it.

The sled/spacers are put together with tiny wood screws (style not material).  The heads are countersunk into the bottom of the cell holder so they do not come into contact with the battery.  I print the spacers with a 75% infill.  I drill a tiny pilot hole and do not have any cracking issues.  I also get a surprisingly tight hold.  


Leaf-Spring Negative End:
https://www.digikey.com/product-detail/en/keystone-electronics/209/36-209-ND/151583

Leaf Spring Positive End:
[/url][url=https://www.digikey.com/product-detail/en/keystone-electronics/204/36-204-ND/227461]https://www.digikey.com/product-detail/en/keystone-electronics/204/36-204-ND/227461

At first I used the 209's on both ends.  But the contact area on the 209 is very large.  I did not like it on the positive end AT ALL!  The contact area on the 209 is large enough to risk bridging the positive contact with the cell shoulder if not perfectly lined up.  Switching to the smaller 204 on the positive end makes it closer to fool-proof.


Good call on the key hole for the cable end.  I will work something like that into the design.
<Tested Inventory Capacity 5.42 KWH>
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