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IR of Leaf cells.
#1
Hey, has anyone done a resistance check on Leaf cells and is it of any use for pre purchase?
Cheers in advance.
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#2
(05-07-2020, 10:17 AM)camthecam Wrote: Hey, has anyone done a resistance check on Leaf cells and is it of any use for pre purchase?
Cheers in advance.
 camthecam,


Any and all batteries have an IR. Now what is acceptable for each chemistry (Pb, NiCad, NiMH, etc) that I do not know.
Except I do know Li-ion especially 18650 cells. Generally speaking lower is better. The less internal resistance a battery has the faster it will charge and the better it will perform.
Now I am sure that a leaf cell has a manufacturer's spec for IR be nice to find out.
Pre purchase IR test........ Well yea. Would you by a horse without looking at its teeth? Of course if it is a gift horse....................

If I could have tested the IR of all the cell in the laptop batteries before I broke them apart I would have saved a ton of time while harvesting over 8000 (many of them never made it into the spreadsheet because of IR) cells and getting ~1200 usable cells with proper IR and SOH.

I now break packs apart check IR if cell is not acceptable I do not spend any more time on it.

Now mind you I kept the IR, mAh, and SOH in the packs I am building to a very close tolerance. By no means do I only have 1200 cells out of a recorded ~6000 that are good. There are a bunch of LG, Sony, BAK, etc. that have high IR from the get-go with a very good SOH. Those I will use for another purpose, just not in a Powerwall where I want the best matched cells I have.

So yea in a long winded roundabout answer to your question yes I would check IR and try to get the leaf cells with the lowest IR and try to match all of them as close as possible.
Wolf
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#3
Remember reading a post on larger cells like these & IR of good cells with some voltage eg maybe 2.5V or more would be very low eg 10 milliOhms or less (vs an 18650 at maybe 60 or so) - it'll be hard to read that low...
Running off solar, DIY & electronics fan :-)
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#4
Some of my leaf cells are 6 milli ohms. (X6 measured)
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#5
(05-07-2020, 01:14 PM)Redpacket Wrote: Remember reading a post on larger cells like these & IR of good cells with some voltage eg maybe 2.5V or more would be very low eg 10 milliOhms or less (vs an 18650 at maybe 60 or so) - it'll be hard to read that low...

Redpacket,

With a proper 4 wire tester like a YR1030+ or a RC3563 you can get way lower than 10mΩ.

YR1030+ spec



Wolf
For Info Google Drive

Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
 [Image: em2566%20(1)__19172.1521541365.jpg?c=2]

Not your average Wolf       
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#6
Leaf cells I don't know, but I have tested some other EV cells (Fiat 500e) and got IR valves as low as 0.5 mΩ which is pretty bonkers.

All that really matters is how it stacks up against a healthy cell of the same time. There no set good or bad range without knowing what was supposed to be on the spec sheet. Your equipment and testing process matters as well. Be sure to use something that can actually measure it properly like a 4 wire tester.

I use the iCharger with balance leads attached, and it seems to be a pretty good job.
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#7
Thanks guys, that’s awesome.
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#8
Also, can you wire leafs as 7s using centre bolt. If there is no fusing or whatever then its just the physical size of internal wiring that would limit current yes/no?
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#9
(05-09-2020, 10:56 PM)camthecam Wrote: Also, can you wire leafs as 7s using centre bolt. If there is no fusing or whatever then its just the physical size of internal wiring that would limit current yes/no?
They are 2s2p pouch cells.  There isn't really 'internal wiring', just terminals connected to the tabs of the pouch cells.   Here's a youtube showing a teardown...  "Nissan Leaf Gen1 Battery Destructive Teardown - What's Inside & What is a "Pouch Cell"?"    https://youtu.be/ibCLe_w-4no 

You can wire 4 units as 7s but you'll have a left over (unused) set of pouches.
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#10
But then - have two and use the spare one with the second pile. 3 1/2 + 3 1/2.= 24v.
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