• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

power source of lithium battery pack

Leong

New Member
Hello, i desire to make a 6cell 24v lithium battery pack with connected to 6s 24v 15A Bms. I already know the connection of the battery to bms. May i know what power supply should i use to charge my 18650 battery pack.

Below picture is my Bms board and battery specification.
1585273903483.png
1585273970716.png
 

audioguru

Well-Known Member
Most Helpful Member
Why am I writing this? It is obvious:
The BMS extremely overloads the battery.
1) The battery max charging current is 2A but the BMS is 15A.
2) The battery max discharge current is 10A but the BMS is 15A.
3) The battery max charging voltage is 4.2V x 6= 25.2V but the BMS is 25.5V.
4) I think the battery will soon die since the BMS has an overdischarge voltage Way Too Low at 2.55V. The battery is almost useless at 3.0V or 3.2V so why not stop discharging to less voltage?
 

Leong

New Member
so i need to change the BMS board to 10A right if not the battery are not protected? And then the input power source adapter can i use 24v 5A or 24v 2A.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
A multi-cell lithium battery needs both voltage protection and charge balancing.

That board does not have balance capability; the typical effect is the battery stops charging as soon as the first cell reaches the cutoff point, regardless of the charge in the other cells.

I'd not be too concerned by the overall BMS current ratings - those are last-resort fault protection and the working conditions should be defined by the charger in use and a fuse for discharge limiting.


The important thing is the protection board rating is higher than the working charge and discharge currents & those are less than the cell ratings.

What you do not want is a false trip when the battery is within safe range.


If your load current will be well under 8A, one of these may be suitable - they are available from many sellers on ebay:



Whatever you use, you MUST also use a charger with a regulated output voltage and an appropriate current limit - that is a separate thing again from the cell protection stuff!

If the BMS protection starts limiting things (other than for balancing) the cells are being pushed beyond their proper limits.
 

audioguru

Well-Known Member
Most Helpful Member
I suspect that the thread starter and many other people wrongly think that a Battery Management System also has a charger circuit in it.
The confusion is probably caused by poor translation from the original Chinese.
 

Latest threads

EE World Online Articles

Loading

 
Top