small (10 Ah) cells?

[kylerlaird]

I've been making e-bikes for my family. I've been using purchased lithium ion batteries, but I have not been satisfied with them. I'm mostly interested in building my own so that I can get the form factor that I want. This 10Ah 48V battery is almost exactly what I need for one installation:

Amazon.com : 48V 15AH /48V 30AH Electric Ebike LiFePo4 / Li-ion Battery with 5A Lithium Battery Charger, 500W 1000W 1500W Electric Bicycle Motor (48V 10AH) : Sports & Outdoors

Amazon.com : 48V 15AH /48V 30AH Electric Ebike LiFePo4 / Li-ion Battery with 5A Lithium Battery Charger, 500W 1000W 1500W Electric Bicycle Motor (48V 10AH) : Sports & Outdoors

smile.amazon.com

For $229, I'm quite tempted to buy it but I'd like to start making my own. I looked around for cells and found these:

LiFePO4 38120P (M size) Cell: 3.2V 10 Ah, 100A Surge Rate, 32Wh with 6M screw Terminal - UN Approved (3.0)

5101

www.batteryspace.com

At $23.75/cell, that's going to push the completed battery price up over $400. Not what I was expecting.

I think I have a box of those cells around here somewhere, so I'll probably try making something anyway, but I'm surprised by the cost.

I did find a lot of 16 cells for $288.

LIFEPO4 Battery Cell Authentic headway 10ah 16 cells 38120s high quality | eBay

16 PCS New headway lifepo4 battery cell, 10 ah 38120s, with free accessaries.Exellent performance and high c-rate. We promise all our battery are original new from headway factroy. all battery has production date on it when it was finished at factory,all our battery are latest new.

www.ebay.com

That's still way more than the $229 complete battery. What's the deal? Are those batteries using a cheaper (tabless/studless) cell format? Am I just not looking in the right place for cells?

 

[Frank in Thailand]

A good start is to use Alibaba/Ali express.

That is the start for Saving.

Next step is the voltage / capacity.
15 cells are 48v, 16 are 51.2v

And capacity..
10Ah sweet smile..
(I have 1016Ah solar home setup)
not petronising

This forum is usually for higher capacity and slow charge and discharge.

there is an extensive E-bike forum that probably can answer you better.

thr challenge is BMS, not so much the cells.

high quality cells give good energy wether they are lithium ion or LiFePO4.

and that's what you need.
high quality as you need fast discharge and fast charge.

the first offer doesn't inform a lot.
just a price...

how much power will you use draw from the cells??

Tremendous difference between 250 and 1000 watt E-bike.

Also what you are planning to have for discharge time.
Hours slow or 30 minutes fast?

Good quality LiFePO4 or li+ion both will work fine for +2000 cycles.
Low quality reduce quickly after 500 cycles or so.
They still work, but depleted fast.

Depending on your wishes spending every year 250 or one time 500 for many years....

 

[Frank in Thailand]

The Amazon page does let you contact the seller (builder) who can customise to your needs.

Benefit from Amazon is it's warranty.
That comes at a cost.
Same pack is on Alibaba probably about $150,-
And the standard "Chinese warranty"
(Not arriving or dead on arrival, not a problem. Not function properly...
That's a challenge to get money back)

Depending on your situation and budget, you choose.

The battery pack you shown has its shrink wrap, BMS and spot welded cells.

Build your own is fun but potentially dangerous.

A simple 12v battery and contactor make a fine DIY spot welder for Zinc strips.

Your E-bike will shake.
Loose battery spot weld will give fire.

It's a fun and great project.
Especially when you have several E-bike and need to build more then one.

The savings won't come from one battery, but building 2 or 3 for each bike, the initial costs are back soon.

Quality cells.
High charge and discharge rating and (matching) low internal resistance are important.

Probably build, they can last you for years and years.