Feedback for ebike battery build: 20s 40ah lithium polymer pouch

[owhite]

High Capacity Li-ion Battery 3.7v 40ah Li Polymer Battery

Battery Type: Li-polymer
Nominal Capacity: 40Ah
Nominal Voltage: 3.7v
Dimension: 8x104x345mm
Weight: 650gm
Internal Resistance: ~1mohms
Discharge rate: 5C 200A
Max discharge rate: 8C 320A
Cost: $40 USD

Does anyone have an opinion about the downsides of using these batteries to build a 20S1P, 72v pack that would deliver 40Ah, 200A continuous discharge? Comments would be quite welcome. I have a lot of experience with power electronics for other (non-ebike battery pack) projects and I'm not worried about the completing the build, so other than cost I dont see a lot of downside. I'm planning on running a QS205, and have yet to purchase the controller

what's not to like!?

Owen

Link and picture included below.

https://www.aliexpress.com/item/329...0.0&pvid=c2850760-28f2-4b3e-9d4c-5ce274767516

 

[owhite]

Okay, might as well shout out some some additional information I've learned from looking around on endless-sphere.

Searches using the keywords:

"SPIM08hp" and
"A123 Pouch Cell"

and "SPIM08hp" has some useful hits on youtube. Right now I'm not drawn to the SPIM08hps because at least right now when you search for them on the googles most of the hits appear as these guys coming from the "pre-owned" market. Perhaps they're yanked from UPSs?

As for connecting the pouches it looks like the state of the art is either clamping approaches:
https://endless-sphere.com/forums/download/file.php?id=247979&mode=view
https://endless-sphere.com/forums/download/file.php?id=277057

one of which resulted in a nice tight bundle in the end:
https://endless-sphere.com/forums/download/file.php?id=277055

another approach for connecting to hit them with a hole punch on the tabs, and place rivets:
https://youtu.be/KKxGZiNDlho?t=480

Some people seem content with essentially lashing packs together with kapton tape:
https://youtu.be/QHk5hkRCzrc?t=214

plus cardboard which is a nice touch in case you need a little more firestarter with your ruptured cells.

I also came across some nice cell holders:
https://cdn.shopify.com/s/files/1/2398/3077/products/20200315_142929_1024x1024@2x.jpg?v=1592845205

which seem like a very sensible idea. This was also a nice build:
https://endless-sphere.com/forums/viewtopic.php?t=105515

Right now since I have access to some CNC machining equipment I'm leaning towards making a custom cell holder, and using a variant of the riveting method for connections. I have a nice aircraft riveter that could place nice quality copper rivets - I'm thinking that in combination with nickel strips which could be used for solder connections seems like a reasonable way to go.

Finally, it's been noted that since the tabs involve aluminum which can oxidize, somewhere on the way I read the suggestion that NO-Ox-ID-A-Special should be used at the contact point of the the aluminum to help reduce corrosion.

Again, comments are very much welcome on the benefits or downsides of using these pouch cells.

I'm still leaning towards 24s1p of these:
https://www.aliexpress.com/item/329...0.0&pvid=c2850760-28f2-4b3e-9d4c-5ce274767516

 

[MadRhino]

This size of low C rate pouch cells are usually crap. I’d say 50% chances, if you are a gambler. :wink:

 

[owhite]

are there more reliable sources for lithium pouch batteries? where does turnigy get them for their packs?

 

[owhite]

So, this thread doesnt seem to be gettin a lot of traction but I figured I'd post some more information.

The following is a summary of ratings for a number of pouch cells, and a comparison to two popular 18650 cells:

The links for each row are posted below. So what I'm taking from this information is there seem to be two classes of pouch cells floating around - one that operates around 5-8 C and others (in green) that are 25C. For the higher Cs that cost / Wh is basically double, but are also lighter. For any combination that gets me to 72v and >150A continuous they all cost around $600-$1,000, while some of the 25C jobs would presumably would mean I could travel farther.

The pouch cells compare just fine with 18650 cylinders, one thing I found interesting is the cycle life of 18650s is usually HALF of pouch cells - so in a sense I'm not sure prices compare well at all. Even if the cost of round cell are equal, you'd still be retiring those packs sooner than pouch cells. So if any of these manufacturers could be trusted links 3, 4, 5 the proposition seems to be: "hm, very high ampacity, lasts longer, and weigh less than any comparably priced 18650".

o

Link1 https://www.aliexpress.com/item/329...68#1000022185#1000066055#0_668#3468#15609#252
Link2 https://www.aliexpress.com/item/329...68#1000022185#1000066055#0_668#3468#15609#252
Link3 https://www.aliexpress.com/item/328...AlpZCqxLrHzYHfCKl9saAorAEALw_wcB&gclsrc=aw.ds
Link4 https://www.aliexpress.com/item/328...AlpZCqxLrHzYHfCKl9saAorAEALw_wcB&gclsrc=aw.ds
Link5 https://www.aliexpress.com/item/328...AlpZCqxLrHzYHfCKl9saAorAEALw_wcB&gclsrc=aw.ds
Link6 https://www.aliexpress.com/item/330...earchweb0_0,searchweb201602_,searchweb201603_

 

[E-HP]

So, this thread doesnt seem to be gettin a lot of traction but I figured I'd post some more information.

You may get more feedback on the battery forum. Not everyone lives in a house instead of an apartment, and has a place (preferably away from the house or outdoors) to charge and store large lipo packs.

 

[owhite]

noted.

 

[kite_rider]

Sorry to see you didn't get more feedback on this. I'm currently trying to build a 4S7P battery out of the spim08hp cells and can say that I really wish I had the plastic holders that allow you to bolt it all together. So far I'm putting a rivet into the tabs with nickle strip (from an 18650 spot weld build) so I can solder wire to it. I can't seem to solder onto those tabs nor have I been able to spot weld them either.

Have you found any sources for the plastic holders? They were on Battery Hookup (where I bought the cells), but not any longer...

 

[999zip999]

https://batteryhookup.com/collections/accessories/products/spim08hp-cell-holder
I got those sales new in a box and yes I would copper rivet the tabs together as I put blocks and bolted it between plastic and alternating aluminum blocks it was a nightmare threaded through rod.
I also built a pack with A123 20 amp hour cells with tabs on same side which I feel is much easier. Measure the shelves must the bus bar and make a battery of cardboard the size that it's going to be and see if it fits where you need it to fit before you buy any cells

 

[kite_rider]

Thanks for the link on the plastic holders. I guess I've had a hard time with searching for stuff on the Battery Hookup site since I tried (and failed!) to find them on that site in the past. I've also since reviewed this thread for even more ideas on how to work with these cells (which you've also made a nice contribution too);
https://endless-sphere.com/forums/viewtopic.php?f=14&t=106666&p=1573217&hilit=spim08hp#p1573217

I was inspired by the guy who was using the 'clam clip' method in that thread and am thinking I"ll attempt a 'quick' 7S1P build for an old e-scooter that I've got in the garage to see how it works. Those stainless steel clips are not easy to source, so I'm going to try to use these plastic clips over a sandwich of the two battery tabs over a nickle strip with a sense wire soldered to it. I'll give it a go since it's no-destructive to the cells and worth a try.
https://www.amazon.com/Refills-No-Slip-Clip-OfficeGoods/dp/B07CMDJ53D

Another note, the guy who used the clips taped all the edges of the pouch. Anyone else having trouble with the pouch edges being electrified? I've been adding a second layer of tape on the edge of the tab to keep my tab connection from leaking over to the foil pouch, but had hoped that the pouch was not directly connected to either tab.