First DIY pack 24s7p

Batteries, Chargers, and Battery Management Systems.
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adamcooks   1 mW

1 mW
Posts: 17
Joined: Jul 15 2015 1:28am

First DIY pack 24s7p

Post by adamcooks » May 12 2020 1:16am

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
24s7p battery rotated.jpg (373.31 KiB) Viewed 261 times
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.

Vbruun   100 W

100 W
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Joined: Sep 26 2019 8:42am

Re: First DIY pack 24s7p

Post by Vbruun » May 12 2020 6:40am

Not an expert, but 18-19 looks a bit challenging to get enough material for counducting 100a :)

bww129   100 mW

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Posts: 35
Joined: Apr 14 2020 7:44am
Location: Lancaster PA, USA

Re: First DIY pack 24s7p

Post by bww129 » May 12 2020 7:27am

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.

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pwd   1 kW

1 kW
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Joined: Oct 11 2011 12:01pm
Location: Ontario, Canada

Re: First DIY pack 24s7p

Post by pwd » May 12 2020 7:51am

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):
viewtopic.php?f=14&t=84412&start=225#p1489521
Commuter/Street Build viewtopic.php?f=6&t=98286:
Rocky Mountain Element
Magic Pie 4 front + Leafmotor 1500 rear w/ WCEC 18fet
Samsung 40T 14S7P

Offroad Build viewtopic.php?f=6&t=102195:
2019 Rocky Mountain Blizzard 20
Cyclone "3kw" 13T motor to 36T chain ring then 32T chain ring to 11T-46T Cassette
em3ev 14S5P 30Q or 14S6P 25R pack

adamcooks   1 mW

1 mW
Posts: 17
Joined: Jul 15 2015 1:28am

Re: First DIY pack 24s7p

Post by adamcooks » May 12 2020 11:02am

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
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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
old pack.jpg (433.58 KiB) Viewed 213 times

adamcooks   1 mW

1 mW
Posts: 17
Joined: Jul 15 2015 1:28am

Re: First DIY pack 24s7p

Post by adamcooks » May 13 2020 1:13am

layout3.jpg
layout3.jpg (283.26 KiB) Viewed 193 times
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
layout3.jpg (299.63 KiB) Viewed 193 times
Yellow are the interconnection between parallel packs outlined in black.

adamcooks   1 mW

1 mW
Posts: 17
Joined: Jul 15 2015 1:28am

Re: First DIY pack 24s7p

Post by adamcooks » May 15 2020 4:37pm

layout5.jpg
layout5.jpg (422.93 KiB) Viewed 150 times
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.

bww129   100 mW

100 mW
Posts: 35
Joined: Apr 14 2020 7:44am
Location: Lancaster PA, USA

Re: First DIY pack 24s7p

Post by bww129 » May 15 2020 5:30pm

That's a massive improvement. Well done.

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