First DIY pack 24s7p

adamcooks

1 mW
Joined
Jul 14, 2015
Messages
17
After letting my bike sit for a couple of years, I decided to resurrect my ebike and build a new battery. The layout of my old battery that was bought on ebay, which mostly used some hexagonal packs layed out in a triangle. I got myself a kWeld as my next pack will be a 12S for my daughters dirt bike. Id like some advice on the layout of this pack of new 4000mAh 40t's. This is a 24s7p setup, with a 100A BMS from LLT ( I hope, they're not so responsive but I purchased one from their website ).
24s7p battery rotated.jpg

Do I assemble the Parallel pack first or glue the whole thing together before welding the nickel? Are there any more efficient layouts for a triangle pack? Any advice is welcome, this is my first pack.
 
Not an expert, but 18-19 looks a bit challenging to get enough material for counducting 100a :)
 
Ideally each cell in the row of 7 would have a connection to the next row of 7 cells for the lowest resistance. The hexagonal groups aren't optimal in this regard. You'll obviously have to get a little creative, but I would try groups in a row of 4 and a row of 3 like the ones you've numbered 8 and 21.
 
I'm also in the process of building a 40T pack. bww129 has said it. Check out this thread. I picked up some good tips (scroll down past my post):
https://endless-sphere.com/forums/viewtopic.php?f=14&t=84412&start=225#p1489521
 
Thank you for your input, I reworked the layout a touch to address the light connection between 17 and 18. I added traces on this photo to help me figure out where to put the nickel. I only did one side, I think the the other will be pretty obvious, I will just repeat the pattern. I think that I will put the BMS in the space that I made by moving those packs.
layout2.jpg

This is the pack that I am replacing, I think that the new one, although not as densely packed, will be more efficient electricly.

old pack.jpg
 
layout3.jpg

So I think i figured out why I chef for a living instead of design battery packs. I spent a few hours trying to figure out a better way to arrange my parallel packs then the hex arrangement of my original pack. IS there any sofware that will optimize layout in a given space and shape?

Does the interconnectivity of the parallel cells play a large role in efficiency. Not using the hex arrangement I found that I had to have single cell rows with a single long strip of nickel connecting up to 4 cells. Is that bad? Also I was able to get more connections between parallel packs but was still limited to 2 connections between some packs. IS it better to have more consistent dual connections through the pack as in the hex arrangement or have multiple connections on most of the packs and just a few with two?

layout3.jpg

Yellow are the interconnection between parallel packs outlined in black.
 
layout5.jpg

Someone on the facebook battery group really stepped up and helped me with the layout. A perfect 24s7p. now to glue it together, BMS from LLT showed up and I'm just waiting on a few connectors at this point.
 
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