2 Battery Hookup Cell level fusing on top of each other?

[TysonScott]

Im planning my fist battery pack build, I am looking at doing 20s 8p, simple design 20 cells long all connected in series and 8 cells wide for parallel 160 total. I need 7000w peak for a tangent ascent motor so 7000/72v = about 100a. 100a/8= 12.5a per cell. I was wondering if I can stack 2 of these battery hookup cell level fusing sheets on top of each other for 6a constantly and 16a peak?
https://batteryhookup.com/products/...8650-cell-level-fusing?variant=34549080457378
at 6 amps constantly that is about 3500w which is more than enough I believe. also since I'm doing 8p instead of their max 6p that they sell, should I get 4 4p sections for 2 sides with 2 stacked on top of each other?

for cells I was looking at 3200 mh1 that say 10a constant and 17.5 peak is this a good budget pick? any recommendations?

 

[harrisonpatm]

Everything else aside, I wouldn't recommend using the nickel fuse sheets for a mobile battery build. Have you used them before? You'll find that the thin fuse section is quite flexible, meaning that it's fragile. I have no data to support this, but I believe the vibration of a e bike is going to slowly wear away at those fuses. Especially if you stack one on top of the other; the two thin fuse sections will be touching, vibrating, and wearing away against each other. They're more for stationary powerwall builds. The point is that the fuse will blow if one secondhand, salvage cell shorts and starts to overheat; the fuse will blow and cut off that single cell from the rest of the pack. In fact, the whole point of them is for low-discharge cells, kinda the opposite of high-drain ebike packs.

Why not use something like this? https://www.aliexpress.us/item/3256803041990818.html?spm=a2g0o.productlist.0.0.4807705feBxHjt&algo_pvid=b82df505-b588-4de2-9556-935338f3e827&aem_p4p_detail=2022100907071212434617890511740004508432&algo_exp_id=b82df505-b588-4de2-9556-935338f3e827-5&pdp_ext_f=%7B%22sku_id%22%3A%2212000024752571804%22%7D&pdp_npi=2%40dis%21USD%2148.44%2123.25%21%21%21%21%21%40210318c216653244326256564ed94b%2112000024752571804%21sea&curPageLogUid=bDKhOhcWrxSW&ad_pvid=2022100907071212434617890511740004508432_6
They're designed for higher drain.

As for your geometry, you mentioned that you're doing a simple design, 8 cells by 20 cells, simple rectangle. If that's the case you don't need 8p sheets, you just need 2p strips, 8 cells long, for each series connection. Does that make sense?

 

[TysonScott]

Everything else aside, I wouldn't recommend using the nickel fuse sheets for a mobile battery build. Have you used them before? You'll find that the thin fuse section is quite flexible, meaning that it's fragile. I have no data to support this, but I believe the vibration of a e bike is going to slowly wear away at those fuses. Especially if you stack one on top of the other; the two thin fuse sections will be touching, vibrating, and wearing away against each other. They're more for stationary powerwall builds. The point is that the fuse will blow if one secondhand, salvage cell shorts and starts to overheat; the fuse will blow and cut off that single cell from the rest of the pack. In fact, the whole point of them is for low-discharge cells, kinda the opposite of high-drain ebike packs.

Why not use something like this? https://www.aliexpress.us/item/3256803041990818.html?spm=a2g0o.productlist.0.0.4807705feBxHjt&algo_pvid=b82df505-b588-4de2-9556-935338f3e827&aem_p4p_detail=2022100907071212434617890511740004508432&algo_exp_id=b82df505-b588-4de2-9556-935338f3e827-5&pdp_ext_f=%7B%22sku_id%22%3A%2212000024752571804%22%7D&pdp_npi=2%40dis%21USD%2148.44%2123.25%21%21%21%21%21%40210318c216653244326256564ed94b%2112000024752571804%21sea&curPageLogUid=bDKhOhcWrxSW&ad_pvid=2022100907071212434617890511740004508432_6
They're designed for higher drain.

As for your geometry, you mentioned that you're doing a simple design, 8 cells by 20 cells, simple rectangle. If that's the case you don't need 8p sheets, you just need 2p strips, 8 cells long, for each series connection. Does that make sense?

Yea that makes sense. After I watched some more videos I realized they look wimpier than I though. I like to hit big jumps and dh tracks and doing so I crash also so Mabye not the best idea... I was looking at nickel strips like that, but I'm not sure how to figure out how thick to get or if I should stack 2.

 

[harrisonpatm]

https://www.youtube.com/watch?v=QMQYfk2RKtU

The entire video is educational, he does a particularly clean and tidy job for such a big pack. But in particular, watch 1:35-2:45, where he does the most concise explanation I've seen on how much nickel to use.

 

[amberwolf]

I like to hit big jumps and dh tracks and doing so I crash also so Mabye not the best idea...

You might be better going with large format cells that don't require a lot of potentially-damageable (from vibration, shock, twisting forces, etc) interconnects that a pack made of multiply-paralleled smaller cells will likely have. (in the event of damaged interconnects, you can end up with groups that have too few cells to support the required current, and overstress them, especially if you start with a pack that is built to just barely support the max loads you'd be putting on it, instead of overbuilding it by half or more to leave room for that kind of problem, or aging, etc).


If you have room in the build for them, using packs such as some of the ones from Batteryhookup and the like that come already in their reasonably heavy-duty mounting frames would probably be a better choice. You might have to alter the way some cells connect inside to make different numbers of series cells, and probably remove/discard any internal electronics / BMS, but the modules could be bolted together as a solid block and then bolted to your frame, directly or thru shock-absorbing system/material/etc. if needed.

What they have changes over time, but some examples:

If I had the money I'd get one of these nicely-built ones for my cargo-hauling/commuting purposes and rewire the insides (assuming paralleled cells that can be unparalleled) for 14s or higher (from the 8s they come as):
https://batteryhookup.com/collections/whats-new/products/vw-8s-29-2v-233-1ah-6-81kwh-ev-module-100-kwh


Or a couple of these and just series them for 24s
https://batteryhookup.com/collections/whats-new/products/samsung-ev-lithium-ion-12s-44-4v-47ah-2-07kwh-module


This one isn't as interesting for my usage, but might work for yours
https://batteryhookup.com/collections/whats-new/products/samsung-12s-43-2v-8-5ah-367-2wh-lithium-ion