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Chris's Build Thread
#31
More work on the bus bar design.

   
   

(10-28-2018, 08:56 AM)Redpacket Wrote: The problem looks like you need to extend the exposed tab part so you don't risk pinching the pouch outer layer.
Maybe use some thin copper sheet eg 30mm x 50mm, fold in half (on middle of 50mm) + punch/drill hole for rod.
Then solder copper part to cell tab.

I have some similar pouch cells & they are assembled with tabs through PCB slots, folded 90 deg & soldered flat.  4 cells to a PCB.


Thanks for the input. I think I am abandoning the threaded rod idea. I will either get the bus bars I am designing made or use stand-offs that are small enough not to engage with the pouch. Only thing that might save the threaded rod idea is some spacers as Sean posted. I just haven't looked around for that yet.
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#32
So I have ordered some stand-offs and spacers, enough for one pack to test that.

I also have an updated rendering. I have quote requests out for the bus bars, so we shall see what they come back with.

   
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#33
Mocked up a version with 11/32" (8.73125mm) aluminum spacers. There will be spacers between the acrylic and terminals as well of course.

       
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#34
I made a mistake in my drawing and the cells were 8.91mm causing me to choose the wrong spacer size, 8.74mm. So after fixing that (cells are average 8.45mm), I ordered 100 7.94mm and that should do it. I might need shims between the cells and the acrylic to make sure the cells are properly compressed. But the idea seems to work.

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#35
Lookin good
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#36
What rate of charge/discharge will you be wanting to put through the assembled packs ?

You might need to make use of much more contact area available on the tab if you are expecting high amps, you will also likely need clamping plates with far greater rigidity when you start charge/discharging them, as even at low rates the acrylic will deform at the midpoint.
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#37
(11-02-2018, 09:17 AM)Sean Wrote: What rate of charge/discharge will you be wanting to put through the assembled packs ?

You might need to make use of much more contact area available on the tab if you are expecting high amps, you will also likely need clamping plates with far greater rigidity when you start charge/discharging them, as even at low rates the acrylic will deform at the midpoint.

80A charge, 138A discharge max to the entire bank. Each series string will be 14s25p. Three of these strings in parallel making 14s75p in total.

So:
-Charging-
Each string will see ~27amps, and thusly each pack (roughly)
Each cell will see ~1.08amps
This looks safe with this configuration

-Discharging-
Each string will see ~46amps, and thusly each pack (roughly)
Each cell will see ~1.84amps
This looks safe as well.

Correct me of my math is off, but this all looks good to me. I think I will do some heat tests with a camera to check in my prototype on Monday.

Regarding the acrylic, it is 0.25" thick. At 8.75" x 6" it would take a great deal of force to warp these much if at all, specially at the charge/discharge rates I am looking at. Since many packs are held together with tape and do fine, I figured 0.25" acrylic with 0.25" threaded rod should be plenty.
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#38
Its been a while since I posted. Progress is being made, 28 of the 42 packs are built. Permit paperwork is submitted to the AHJ. I haven't decided where the longmons are going to be mounted, but definitely not where they are in the picture.

           
Korishan, Redpacket, jdeadman like this post
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#39
What's your overall capacity going to be ?

I have 114kWh of Leafs cells for a home project sat waiting.

mike likes this post
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#40
(12-18-2018, 08:50 AM)Sean Wrote: What's your overall capacity going to be ?

I have 114kWh of Leafs cells for a home project sat waiting.


Only ?? Big Grin



(this is just not fair....)
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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