Help with my first Ebike battery pack and project

[JakeTheDog420]

Hello all!

First let me introduce myself to the forums, my name is Brad. I have been thoroughly obsessed with the design and development of this project now for the past several months.

The end goal is having both myself and my girlfriends bikrs converted to fully electric bikes with batterys of at LEAST 9ah.

I purchases a few cheap Chinese cells to play around with knowing they will probably short or die and was basically just a test to see how it all goes together.

I managed to blow my first BMS with them! Aha

Anyway, now after realizing my mistake on the wiring of the BMS and altering the overall design of my project to fit in with a few educational videos I watched I would just like to know if everything will go well with my proposed design.

In the picture you will see two things. First is a diagram I made of a working 13s2p pack. That is the proof of concept. It shows both the front and then if you imagine flipping it over so you can wire the bottom halve too.



The second set in tbe image is the front halve I propose to do. The overall cell count is 52 so from my understanding of things I've simply increased the numbee of cells in parralel and as long as I weld everything as proposed it should all work as expected?

Would appreciate anyones help who has more of an understanding than I do myself.

Thanks for taking the time to read my slightly long post!
Regards,
Brad

 

[JakeTheDog420]

If anyone could checkout my thread and give me any pointers id really be greatful!

https://endless-sphere.com/forums/viewtopic.php?f=2&t=81059

 

[fechter]

It will work like that but not ideal.
Ideally you want each cell to have its own series connection, since these carry all the current. The parallel connections between cells in the same group don't carry any current normally. They are just there to ensure balance and monitoring by the BMS.

How are you going to weld the cells? What are you using to make the connections?

 

[JakeTheDog420]

It will work like that but not ideal.
Ideally you want each cell to have its own series connection, since these carry all the current. The parallel connections between cells in the same group don't carry any current normally. They are just there to ensure balance and monitoring by the BMS.

How are you going to weld the cells? What are you using to make the connections?

Hello Fechter and thank you for your reply!

I am welding all connections using a Battery Spot Welder. Originally I had purchased a relatively cheap 3Kw machine from online but after receiving it I noticed that the two copper electrodes were not protruding from the machine enough for me to be able to weld together the correct amount of cells in the way I had original anticipated.

Because of this I have now purchased a new Spot Welder. This one is very popular amongst DIYers. It has multiple pulse options, an input for a soldering iron and most importantly, as well as two prongs from the machine itself it accepts a welding pen which will allow for me to make packs of a much larger size.

From my understanding of your reply my design will work fine as is however for best result I need to simply give every cell its own series connection? I will alter my design based on my understanding of what you wrote and see if that seems better.


I think for my current test batteries it doesn't matter so much so I will leave their design as is but for the real deal I'll follow your advice as there will be much more Ah involved overall and I don't want to kill all 52 of my cells due to stupidity.

Lastly I assume me altering my designs to follow your suggestions doesn't change the wiring of the BMS?

regards

 

[JakeTheDog420]

Sorry it took me so long to update it but here it is



That will be the top halve of the battery pack I believe?

And that would make this the underneath of that same battery pack. Sort of like if you imagine the cell +13 on the top halve and then turn the pack upside down so that cell +13 is now upside down and on the right. Hence -13



Whats everyones opinions?

And if someone wanted to go for bonus points directing me the right way with my BMS wiring even better

Thanks

 

[JakeTheDog420]

I am making my first ever battery pack, anyone with knowledge of spot welding and BMS please maybe look at my thread? Appreciate all the help I receive!

brad
https://endless-sphere.com/forums/viewtopic.php?f=2&t=81059

 

[fechter]

That layout is much better. On the end groups where the main wires attach, the parallel connection needs to be heavy (take full battery current). The ones between can be fairly small since very little current will go through them.

 

[Wakkabu]

It will work like that but not ideal.
Ideally you want each cell to have its own series connection, since these carry all the current. The parallel connections between cells in the same group don't carry any current normally. They are just there to ensure balance and monitoring by the BMS.

How are you going to weld the cells? What are you using to make the connections?

Hello Fechter and thank you for your reply!

I am welding all connections using a Battery Spot Welder. Originally I had purchased a relatively cheap 3Kw machine from online but after receiving it I noticed that the two copper electrodes were not protruding from the machine enough for me to be able to weld together the correct amount of cells in the way I had original anticipated.

Because of this I have now purchased a new Spot Welder. This one is very popular amongst DIYers. It has multiple pulse options, an input for a soldering iron and most importantly, as well as two prongs from the machine itself it accepts a welding pen which will allow for me to make packs of a much larger size.

From my understanding of your reply my design will work fine as is however for best result I need to simply give every cell its own series connection? I will alter my design based on my understanding of what you wrote and see if that seems better.


I think for my current test batteries it doesn't matter so much so I will leave their design as is but for the real deal I'll follow your advice as there will be much more Ah involved overall and I don't want to kill all 52 of my cells due to stupidity.

Lastly I assume me altering my designs to follow your suggestions doesn't change the wiring of the BMS?

regards

You only need 2 deep, just have to look at technique a bit.

https://youtu.be/5L9hOVG_0RQ

That video gives a clear impression.
Weld the 13 groups 4 wide first. These are the p groups. Then weld the S groups together like in the youtube video.
Staggered or straight should both work

 

[999zip999]

I use a gasket on the pos. end always.