20s2p Battery Build Confusion

[DJB623]

This is my first post here, but I have lurked over the years and found help with other projects over the years. I am not new to the EV space, but I am new to building my own battery pack. I have always avoided it due to the respect I have for these things. I recently acquired the new CYC Photon Gen2, and wanted a small lightweight battery. I believe I am ready to undertake my first build and would appreciate some advice.

I have Ampace JP40 21700 cells. I am looking to build a 20s2p pack. Just about all of the examples I have found show mounting the batteries horizontal, intended for a one wheel builds.

I think I know what I need to do, but wanted to make sure before proceeding. I am planning to use nickel strips I cut on my fiber laser. I think I am overthinking, and I believe I need to swap the batteries on the lower row to be opposite from top to allow the pattern to continue Now in a u shape.

I am waiting until I order a BMS, but was eyeing a Balance 100 24s 150a Smart BMS.

If anyone could provide some advice on how this should be connected, it would be greatly appreciated.

 

[lnanek]

So right now you have two 10s2p strings laid out with no connection between them. Have you considered just doing one long string of 20s2p and folding it in half?

 

[docw009]

Yes. The bottom 20 cells should be flipped around if you want the current to flow back to the other end. There will be one single strip on one end that one cell wide and 4 cells high, There will be a potential bottle neck in the center which has to carry the total current of the battery. Solder some copper braid or wire in parallel.

Will your nickel paddles carry 30-40 amps? How long will the battery last at 30 amps? I really don't know.

Edit: An 8AH battery will last no more than 16 minutes pushing 30A.

 

[DJB623]

I appreciate the responses. I think I know what I need to do. I originally cut them out of copper. I wanted to weld the nickel to the copper, but quickly realized how much energy it takes to weld the copper and nickel together.

I experimented welding the 2 using my fiber laser, not on the batteries of course. In theory it should be possible, but I was really struggling to get the settings right to get them to fuse together reliably.

 

[qi689]

I too just got myself a CYC x1 pro gen 2 about 2 weeks ago... Im sitting on 100pcs new p42a molicel 21700 and was considering doing a 2p build. but considering winter use and voltage sag that is cutting it really thin. So im planning to just build a 20s5p pack and put it in a backpack as the bike im putting it on doesnt have any convenient place to put the battery.. its a 2009 DH bike. Ive been looking for a portable "almost like a saddle" solution where i have 2x long thin battery packs hanging over the upper tube and connect them in paralell so they hold themselfs in place by weigth (and straps), and easy to remove. I dont really wanna be biking around with a battery in my backpack though so also considering the front basket for battery that will look kinda funny but i dont know...

 

[DJB623]

A few of the cyc dealers seem to be offering 20s2p packs, for example this one:

https://www.johnnynerdout.com/product-page/72v-9ah-100a-battery-w-molicel-45b72v 9ah 90a Battery w/ Molicel 45b with Bag | Johnny Nerd Out

I did decided to go a little larger, and I am going to do 20s3p. Which I hope will help a little bit with voltage sag and should give me roughly 12ah.

I like the saddle idea!

I ended up ordering some pre-made copper/nickle bus bars from eBay as I couldn’t get reliable spotwelds to the .2 copper I had. I tried welding them using my mopa fiber laser. I spent a whole afternoon trying to find a setting that would work but couldn’t get a reliable weld there either.

Should have it done this week if I get everything in the mail.