eBike battery build

[Rickstar]

Hi Guys,

I am new here, I am very mechanically minded and electrical to some extent but a little out of my comfort zone.

I have thoroughly researched all the best for bang buck battery building supplies, including 8mm x 0.15 pure pickle strip.

The Kapton tape, nickle strip and battery case should be here in a week or so, so.I started planning, attached is what I have so far, just wondering of anyone with battery building experience could help me with the build.

Cheers
Rick

 

[Chalo]

Understand that using little rinky dink cells in massively parallel arrangement is lazy thinking and sorry use of personal resources.

How many Ah do you need to do the job?

 

[Rickstar]

Hey Chalo,

Thank you for your reply.
Every build I have seen uses either the 18650 or 21700 cells, I thought it was the only option.

I am looking at using the Samsung 50s batteries, 5ah each, so looking at getting 20ah.

 

[Chalo]

Hey Chalo,

Thank you for your reply.
Every build I have seen uses either the 18650 or 21700 cells, I thought it was the only option.

I am looking at using the Samsung 50s batteries, 5ah each, so looking at getting 20ah.

If your existing battery uses 18650 cells, you can disregard 21700 cells. They won't fit in the same space.

 

[Rickstar]

Thanks, it's a brand new build, the case I purchased is for 56 x 21700 cells.

 

[Gruesome]

What's wrong with a 14s4p array? Why are 21700 'little rinky dinky cells'?

 

[gromike]

I'd be more worried about the current draw through the 8mm .15mm nickel strips.
If you have figured that out, go for it.

 

[E-HP]

Thanks, it's a brand new build, the case I purchased is for 56 x 21700 cells.

I might consider other cells if you haven't hit the Buy button yet. I was looking at the 50S cells, but there are a few alternatives that look good on their spec sheets.

The Molicel P50B looks interesting. 60A discharge, 25A charge, so charging at the 6A rating of the 50S would be a very gentle charge rate. Similarly, when pulling 10A with a 60A rating, there should be almost no voltage sag.

https://cdn.shopify.com/s/files/1/0481/9678/0183/files/Screenshot_2024-08-12_110209.png?v=1723474940

If you were in a hurry, you could charge the pack from empty to full in 50 minutes. I've been looking at 21700 cells for a while, for a future pack. Fast charging and little to no voltage sag are two of my main considerations.

That smart BMS looks good on paper. I'm interested in what you think of it once you get the pack together.

The battery technology subforum is another good place on ES to get info/guidance.

 

[Rickstar]

I might consider other cells if you haven't hit the Buy button yet. I was looking at the 50S cells, but there are a few alternatives that look good on their spec sheets.

The Molicel P50B looks interesting. 60A discharge, 25A charge, so charging at the 6A rating of the 50S would be a very gentle charge rate. Similarly, when pulling 10A with a 60A rating, there should be almost no voltage sag.

https://cdn.shopify.com/s/files/1/0...eenshot_2024-08-12_110209.png?Illv=1723474940

If you were in a hurry, you could charge the pack from empty to full in 50 minutes. I've been looking at 21700 cells for a while, for a future pack. Fast charging and little to no voltage sag are two of my main considerations.

That smart BMS looks good on paper. I'm interested in what you think of it once you get the pack together.

The battery technology subforum is another good place on ES to get info/guidance.

Thanks. I haven't purchased the cells yet, I have read great things about the Molicel P50B, the numbers you quoted sound good, so many products out there, lol.
I'll keep you posted once I start using the BMS.
I'll get into the battery technology subforum and snoop around

 

[E-HP]

Thanks. I haven't purchased the cells yet, I have read great things about the Molicel P50B, the numbers you quoted sound good, so many products out there, lol.
I'll keep you posted once I start using the BMS.
I'll get into the battery technology subforum and snoop around

Well I haven't used them, or seen them in a pack build yet, but there's a thread that has some info in that subforum.

Cycle life tests of High Power density cylindrical cells

"Standard Power Rate" test (1C continuous discharge) note: the 1C discharge test is performed at ca 90% DoD (4.15V-3.00V) Test eqiupment: - 2pcs ZKETECH EBC-X0510 - BF-2A four-wire cell fixture (10A version with Nickel plated contacts) - tested in room with relatively stable temperature 23 ±2...

endless-sphere.com

Did you order the temp sensors? I didn't see them on your sheet.

 

[Rickstar]

Did you order the temp sensors? I didn't see them on your sheet.

I Have

Well I haven't used them, or seen them in a pack build yet, but there's a thread that has some info in that subforum.

Cycle life tests of High Power density cylindrical cells

"Standard Power Rate" test (1C continuous discharge) note: the 1C discharge test is performed at ca 90% DoD (4.15V-3.00V) Test eqiupment: - 2pcs ZKETECH EBC-X0510 - BF-2A four-wire cell fixture (10A version with Nickel plated contacts) - tested in room with relatively stable temperature 23 ±2...

endless-sphere.com

Did you order the temp sensors? I didn't see them on your sheet.

I'll do some research tonight and see if I can find how they are in packs.

I am just ordering the temp sensor, wasn't really sure if there was a "best" place to put it

 

[Rickstar]

Well I haven't used them, or seen them in a pack build yet, but there's a thread that has some info in that subforum.

Cycle life tests of High Power density cylindrical cells

"Standard Power Rate" test (1C continuous discharge) note: the 1C discharge test is performed at ca 90% DoD (4.15V-3.00V) Test eqiupment: - 2pcs ZKETECH EBC-X0510 - BF-2A four-wire cell fixture (10A version with Nickel plated contacts) - tested in room with relatively stable temperature 23 ±2...

endless-sphere.com

Did you order the temp sensors? I didn't see them on your sheet.

Just checked the box, it comes with a temperature sensor

 

[docw009]

If this is a cell layout, it could be better. There are going to be spots where current will be concentrated on a single strip, which will require extra layers of nickel. This will happen anyway, but you want to minimize it to a few areas. An ideal layout has none,

They usually sell a metal pattern with the case that will be superior to your diagram, It's usually nickel plated steel, but will still be better for current flow than this. Look at them for ideas on how to organize your cells.



Cases come with cell spacers. I assume you have that included? Don't be gluing cells together w/o a cell form. No kapton tape is needed, except to cover the nickel. I advise buying the adhesive paper washers for the positive ends of all the cells, Commercial batteries use them, you should too.

 

[docw009]

The Samsung 50S seem OK to me. I don't put fuses inside my batteries, figuring the BMS short circuit current protection will suffice if I plug something in backwards, and it has.

 

[Chalo]

What's wrong with a 14s4p array? Why are 21700 'little rinky dinky cells'?

They're uselessly small enough that the OP needs 4P to get enough Ah capacity. That quadruples the interconnections and points of potential failure compared to using cells the right size for the job.

Would you run your bike on C size NiMH flashlight cells? Those are about the same size.

 

[Diggs]

That quadruples the interconnections and points of potential failure compared to using cells the right size for the job.

I forgot what your cell preference is @Chalo ? LiPo pouches?

 

[Chalo]

I forgot what your cell preference is @Chalo ? LiPo pouches?

Whatever is in the automotive module I'm using at any given time. Relevant sized modules are almost all 1P or 2P. I've built my own pack from 25Ah Panasonic PHEV2 prismatic cells, which now a few years later are available in ~50Ah for the same size.

This is the kind that I've put the most miles on in the last couple years. I didn't get mine from this site, but it's pretty clearly the same pack:

Jeep Cherokee PHEV 44v Battery 2.1kWh modules Samsung Cells 12s

PLEASE READ THE DESCRIPTION CAREFULLY. Shipping to Lower 48 USA states only via Ground Shipping. No shipping to PO Boxes. No international shipping including Hawaii, Guam, Puerto Rico. EV modules with high quality Samsung cells! These 44v 47Ah 2.1kWh li-ion modules were originally intended for...

jag35.com

I also use the aforementioned homemade Panasonic 25Ah pack (13S 1P), a Mercedes Benz 12S 2P 20Ah pack, and a 12S 1P pack with 8.5Ah.

 

[Rickstar]

If this is a cell layout, it could be better. There are going to be spots where current will be concentrated on a single strip, which will require extra layers of nickel. This will happen anyway, but you want to minimize it to a few areas. An ideal layout has none,

They usually sell a metal pattern with the case that will be superior to your diagram, It's usually nickel plated steel, but will still be better for current flow than this. Look at them for ideas on how to organize your cells.

View attachment 359132

Cases come with cell spacers. I assume you have that included? Don't be gluing cells together w/o a cell form. No kapton tape is needed, except to cover the nickel. I advise buying the adhesive paper washers for the positive ends of all the cells, Commercial batteries use them, you should too.

Thank you for your input, the configuration was my first attempt, it makes sense now to look at the flow of the factory stamped/laser cut patterns.
Are these the paper washers you are referring to, can I ask the reason for these?
I am using a reention polly box which definitely has the spacers in each side.

 

[Diggs]

This is the kind that I've put the most miles on in the last couple years. I didn't get mine from this site, but it's pretty clearly the same pack:

Interesting...... A bit more of a challenge to configure in tight spaces but definitely something I want to check out next time.

In turn, I've never seen (or even heard of) inter-cell connections failing on packs with 18650 or 21700 cells. Even in the Tesla Model X with over 8,000 cells I've never heard of a problem. Hmmm.......

 

[Chalo]

In turn, I've never seen (or even heard of) inter-cell connections failing on packs with 18650 or 21700 cells.

I've seen it with my own eyes, in both homemade and shady Chinese packs.

Even in the Tesla Model X with over 8,000 cells I've never heard of a problem. Hmmm.......

Tesla has cell welding robots and a six sigma manufacturing facility. Do you? Does that shady Chinese battery-hustling bum?