I am planning to order a battery pack from aliexpress or other online sellers for my new e-bike. I have following questions;

1- I know the brand of battery cell plays an important role. If i order some with a Panasonic or Samsung cell how can i be sure if the seller really uses the original one.

2- Are the chinese made battery cells really that worse than the other asian batteries such as samsung and panasonic.

3- How can i test my batteries. ? What devices do i need and what parameters do i need to look at ?

4- How important is BMS? what things i need to pay attention in a BMS.

5- I read that many people complain about overheating in Batteries. How can it be prevented other than careful using. Do a good BMS system prevent overheating ?

6- Do i need a metal battery pack ? Can i make my own battery pack and install it in the frame using some plastic kind of bag (That i see onweb i don't know what to call for that material)>

I know i ask too many. if you guys can answer some i will be really glad.

I hope i can post my e-bike photos after assembling it.

Each cell should be clearly marked-branded ... including a unique serial number.
Pay with PayPal, and if not genuine, you can get your money back.

Samsung and Panasonic both produce batteries in China now , so ... ?

If you really want to test your batteries ... (Li-ion = LiCo)
You would need a volt - Multi-Meter

Test 1. No Self-discharge
Fully charge
Confirm all banks of equal voltage eg. 4.16V
Note voltages precisely
Remove BMS
Let set for several days
Make note of precise bank voltages
Any with a marked voltage loss indicates a self-discharging cell

Test 2. Equal Capacity
Fully charge
Confirm all banks of equal voltage eg. 4.16V
Remove BMS
Fully discharge (≥3.70V per bank recommended)
Compare bank voltages


A BMS is vitally important ... if you have a defective pack!
A BMS will shut you down and variously protect against some malfunctions and under-over voltages
Tho ... Personally, I view a BMS as a Band-Aid for a defective pack!

BMS might have a thermal fuse - cuts all power if a dangerous overheat occurs?

Hard plastic or hard plastic protection inside bag preferred. Metal would require extra heavy protection inside it to prevent possible short - if damaged.

Thanks a lot for your help. But if the battery pack comes as a set is there a way that i can test them without damaging battery pack while testing ?

And for chinese made cells i mean "Chinese branded". Sorry i miss interpreted.

Quality brand name cells will tend to be very consistent and work well together in a pack, while lesser cells can vary quite a bit and it's hit and miss ( they work fine individually, like in flashlights and the like... but grouped in a pack is a whole other game )

You need to size the pack to your application, if you have a bike that requires a 20 amp capable pack, you should have a pack that can supply that much without killing itself.

What motor/controller are you using ? and exactly what pack are you considering ?