Common pack design mistakes, how to avoid?

Batteries, Chargers, and Battery Management Systems.
jdvmi00   10 µW

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Re: Common pack design mistakes, how to avoid?

Post by jdvmi00 » Nov 12 2020 9:40pm

fechter wrote:
Nov 12 2020 6:15pm
The picture didn’t come out.
Yes you want the current in all the cells to be nearly equal. With only 3p this won’t be hard.
Thoughts on this?
Terminal.jpg
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papasapien   10 mW

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Re: Common pack design mistakes, how to avoid?

Post by papasapien » Nov 13 2020 2:20am

i went on reddit and someone told me i need to not have all my output for the negative and positive terminals of my battery pack on just two tabs.( im using the vruzend 2.1 kit) i understand why and the diagram in the beginning of this thread but everyones batteries i see on here seem to do the opposite of what is suggested or am i missing something? can someone help me understand this? how to have good current flow and even draw. everyone seems to just have a slab of wire across their battery pack. i dont understand how thats different then just having it at the end if every cell is already connected.

here is my diagram vs what he suggested. which i know is the right way but how could i do this? pls help thank you. its the last thing i need to understand
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ItsOverRock   10 µW

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Re: Common pack design mistakes, how to avoid?

Post by ItsOverRock » Nov 13 2020 3:46am

Trying to wire 2 of these exact gotrax scooter batterys packs in parallel to double capacity of scooter. Dunno how to go about connecting them together. Need help, here are the pics from the bottom of battery pack to top & BMS.
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fechter   100 GW

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Re: Common pack design mistakes, how to avoid?

Post by fechter » Nov 13 2020 10:31am

jdvmi00 wrote:
Nov 12 2020 9:40pm
Thoughts on this? Terminal.jpg
That looks fine. There won't be much voltage drop in the tabs.
"One test is worth a thousand opinions"

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pwd   10 kW

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Re: Common pack design mistakes, how to avoid?

Post by pwd » Sep 28 2021 2:18pm

I'm back with my 3rd battery build in sight. I'm aiming for a 20S6P configuration but am constrained by the shape of the bike. Here is what I have to work with:

Ignore the Nickle sheet
IMG_20200513_195746-v2.1.jpg
IMG_20200513_195746-v2.1.jpg (108.16 KiB) Viewed 589 times
Does anyone have an suggested layouts to make this 20S6P?
2WD Commuter/Street Build viewtopic.php?f=6&t=98286:
Rocky Mountain Element - upgrades in progress
Magic Pie 4 front w/ Infineon 4 Clone @ 70A phase + Leafmotor 1500 rear w/ Infineon 4 Clone @ 230A phase
Samsung 40T3 20S6P

Offroad Build viewtopic.php?f=6&t=102195:
2017 Scott Big Jon
Cyclone "3kw" 13T motor to 36T chain ring then 32T chain ring to 11T-46T Cassette @ 100A phase
Molicel P42A 21S3P

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RootedSuperuser   10 W

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Re: Common pack design mistakes, how to avoid?

Post by RootedSuperuser » Oct 20 2021 11:01am

pwd wrote:
Sep 28 2021 2:18pm
I'm back with my 3rd battery build in sight. I'm aiming for a 20S6P configuration but am constrained by the shape of the bike. Here is what I have to work with:

Ignore the Nickle sheet
IMG_20200513_195746-v2.1.jpg

Does anyone have an suggested layouts to make this 20S6P?
You don't have to do a 20*6, you can do a 20*2x3 and get the same result. I did this with my 14*2x3 pack and got a perfit 1:1 power share, using nickel STRIPS .... your using sheet so it matters not.

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pwd   10 kW

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Re: Common pack design mistakes, how to avoid?

Post by pwd » Oct 22 2021 12:42pm

RootedSuperuser wrote:
Oct 20 2021 11:01am
pwd wrote:
Sep 28 2021 2:18pm
I'm back with my 3rd battery build in sight. I'm aiming for a 20S6P configuration but am constrained by the shape of the bike. Here is what I have to work with:

Ignore the Nickle sheet
IMG_20200513_195746-v2.1.jpg

Does anyone have an suggested layouts to make this 20S6P?
You don't have to do a 20*6, you can do a 20*2x3 and get the same result. I did this with my 14*2x3 pack and got a perfit 1:1 power share, using nickel STRIPS .... your using sheet so it matters not.
Thank you for the suggestion. The numbers make sense to me but I'm having a hard time visualizing how to connect that. So I would make 3 X 20S2P packs and parallel the discharge leads together?
2WD Commuter/Street Build viewtopic.php?f=6&t=98286:
Rocky Mountain Element - upgrades in progress
Magic Pie 4 front w/ Infineon 4 Clone @ 70A phase + Leafmotor 1500 rear w/ Infineon 4 Clone @ 230A phase
Samsung 40T3 20S6P

Offroad Build viewtopic.php?f=6&t=102195:
2017 Scott Big Jon
Cyclone "3kw" 13T motor to 36T chain ring then 32T chain ring to 11T-46T Cassette @ 100A phase
Molicel P42A 21S3P

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pwd   10 kW

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Re: Common pack design mistakes, how to avoid?

Post by pwd » Jan 17 2022 8:22am

If I did spilt up the 20S6P pack into 20S2P sub packs and put them in parallel; would I also have to paralell all the balance leads for the BMS?
2WD Commuter/Street Build viewtopic.php?f=6&t=98286:
Rocky Mountain Element - upgrades in progress
Magic Pie 4 front w/ Infineon 4 Clone @ 70A phase + Leafmotor 1500 rear w/ Infineon 4 Clone @ 230A phase
Samsung 40T3 20S6P

Offroad Build viewtopic.php?f=6&t=102195:
2017 Scott Big Jon
Cyclone "3kw" 13T motor to 36T chain ring then 32T chain ring to 11T-46T Cassette @ 100A phase
Molicel P42A 21S3P

john61ct   100 GW

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Re: Common pack design mistakes, how to avoid?

Post by john61ct » Jan 17 2022 2:44pm

pwd wrote:If I did spilt up the 20S6P pack into 20S2P sub packs and put them in parallel; would I also have to paralell all the balance leads for the BMS?
No "have to" your call.

But yes that approach lets all the sub-packs to be protected and balanced by just one BMS

simpler is usually better.

Plus the cell/groups will naturally rebalance in use, counteracting the ill effects of unequal draws via the power leads at pack level voltage

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DogDipstick   100 kW

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Re: Common pack design mistakes, how to avoid?

Post by DogDipstick » Jan 18 2022 9:23am

pwd wrote:
Jan 17 2022 8:22am
If I did spilt up the ...; would I also have to ... for the BMS?
I do. yes. I just built a 50Ah 2p Chevy cell pack that I did this so I could run 1 BMS... One 25Ah half, 21 sense lines, and one 25Ah half, 21 sense lines... into +/- discharge leads and a 25 pin DB connector.... Every cell has an output lead and the pairs of 2p come together in a connector to go to the BMS as one signal line.
84v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D You call .. that.. a "glitch:" ? :twisted: (...No Mom. The formula is Kaw > 1(Hr) = Impounded. The math checks out. I'll be fine. ).. :? Broke20Horsies! 17,830w !! :x 1 (pound / second) Hp = 338.24 M^2 Kg^2 / Sec^4 ( :twisted: 1200v? :twisted: ) :| isn't 13" x 27".. Oh nvrmnd :roll: 4+25% = 5 ; 5-20% = 4... 5(1-20%) = 4.. so, to correct the incorrect reading, of 4 ... 4(1+25%) = 5 :confused: Fabricator @BSECo.

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RootedSuperuser   10 W

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Re: Common pack design mistakes, how to avoid?

Post by RootedSuperuser » Jan 20 2022 6:29pm

pwd wrote:
Jan 17 2022 8:22am
If I did spilt up the 20S6P pack into 20S2P sub packs and put them in parallel; would I also have to paralell all the balance leads for the BMS?
Yes

john61ct   100 GW

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Re: Common pack design mistakes, how to avoid?

Post by john61ct » Jan 20 2022 10:28pm

Again, not have to

but certainly is the better way to go.

If only paralleled at the power pair, imbalanced flows creates extra monitoring / balancing headaches

and lower overall lifespan.

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pwd   10 kW

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Re: Common pack design mistakes, how to avoid?

Post by pwd » Jan 21 2022 9:58am

Thanks guys :bigthumb: No free lunch as they say.
2WD Commuter/Street Build viewtopic.php?f=6&t=98286:
Rocky Mountain Element - upgrades in progress
Magic Pie 4 front w/ Infineon 4 Clone @ 70A phase + Leafmotor 1500 rear w/ Infineon 4 Clone @ 230A phase
Samsung 40T3 20S6P

Offroad Build viewtopic.php?f=6&t=102195:
2017 Scott Big Jon
Cyclone "3kw" 13T motor to 36T chain ring then 32T chain ring to 11T-46T Cassette @ 100A phase
Molicel P42A 21S3P

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