BMS quick question

B

Badblue

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Jan 25, 2018
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Can I use a 12V charger on a BMS to balance charge a 24V 8S? The BMS and cells are LiFeP04

I don't see why this wouldn't work as each cell is charged seperately in relation to one another.
 
No you cant Charge 24v with 12v. What your can do is Charge half that 24v battery at a time but the bms Will not like it. Ie not recommended. Get a proper Charger from start
 
Yes if you charge half the pack at a time and switch to the other half of the pack it will work fine. Each half of the pack will be effectively teated as a separate 12V pack. Not ideal but if you are limited on resources it can work. As Daromer said, if you can get a more suitable charger and BMS then go that route, otherwise hook it up and charge 12V at a time.
 
Thanks for the reply. I have 2 small 1 amp 12v auto chargers I can hook up for now.
 
12V 100A 4S BMS Li-ion LiFePO4 LiFe LMO Lithium Battery Protection Circuit Board

So I bought a bunch of these BMS while back and forgot to save the listing which had a more detailed wiring instruction.

I would love it if someone could help me out or point me to a good tutorial.


image_cdsrqd.jpg



image_qaipiy.jpg
 
Not sure what your question is. The diagram you posted tells you everything including the order the cells are to be connected to it. :huh:
 
Korishan said:
Not sure what your question is. The diagram you posted tells you everything including the order the cells are to be connected to it. :huh:
Click to expand...

It says "charger" in 5 locations. I need to run leads to the positive ends of the cells as well. It is not clear to me.
 
Smaller Chargers are cells
B0, B1, B2, B3, B4, B+

Charger P- is for Power Negative. Power in this case would be the load that you are "powering".
Charger C- is for Charging Negative

I ignored the Photoshop/Paint text labeling and looked at the PCB itself. That's where the correct labels are at.
 
Korishan said:
Smaller Chargers are cells
B0, B1, B2, B3, B4, B+

Charger P- is for Power Negative. Power in this case would be the load that you are "powering".
Charger C- is for Charging Negative

I ignored the Photoshop/Paint text labeling and looked at the PCB itself. That's where the correct labels are at.
Click to expand...

Thats kinda what I thought, I just needed some confirmation.

Thank you
 
Korishan said:
Smaller Chargers are cells
B0, B1, B2, B3, B4, B+

Charger P- is for Power Negative. Power in this case would be the load that you are "powering".
Charger C- is for Charging Negative

I ignored the Photoshop/Paint text labeling and looked at the PCB itself. That's where the correct labels are at.
Click to expand...

Is this a 4S BMS?

Why are there B+, B1, B2, B3, B4 .. Thats 5 positive leads? So is this a 5S?

Honestly, the diagram in the pic is useless.
 
Badblue said:
Korishan said:
Smaller Chargers are cells
B0, B1, B2, B3, B4, B+

Charger P- is for Power Negative. Power in this case would be the load that you are "powering".
Charger C- is for Charging Negative

I ignored the Photoshop/Paint text labeling and looked at the PCB itself. That's where the correct labels are at.
Click to expand...

Is this a 4S BMS?

Why are there B+, B1, B2, B3, B4 .. Thats 5 positive leads? So is this a 5S?

Honestly, the diagram in the pic is useless.
Click to expand...

I installed this BMS on my pack but the output is only 0.5V
Something is wrong

image_nxzvcm.jpg


I found these for sale on Aliexpress (I bought them off ebay)
Here is aLINKbut it has the same crappy diagram
It says its a 3s, 4s, 5s @ 12V 100A

I found another pic of it with a different diagram. This is a 3s

image_besgan.jpg
 
It appears to be a 5s BMS, that is intended (by shorting a cell connection) to be usedfor packs with less than 5 in series.

That last diagram shows it configured for a 3spack, showing shorted connections.
 
To add to Seans post, if you wanted to use it on 4x cells, you would
- remove the link between B2 & B-
- connect another cell in series with the others at the right
- link from B2 to the junction of the existing cell & the new cell
- connect the new cells -ve to the B- terminal
See pic:

image_gvmhyg.jpg
 
Sean said:
I wonder what the "shorted" link does ...
Click to expand...

Good question.

Badblue: Can you tell us what the IC numbers are on this chip? (multi-colored box)

image_kittso.jpg
 
What kind of cell holders are these

They look to be solderless with a thread stud at each end

You are using a copper wire buss bar between the threaded studs

Are these custom made?
 
Chablis_m said:
What kind of cell holders are these

They look to be solderless with a thread stud at each end

You are using a copper wire buss bar between the threaded studs

Are these custom made?
Click to expand...

The cells are 38120s. They have threads on the terminals, unlike most 18650s. The holders appear to be 3D printed.
 
Korishan said:
Sean said:
I wonder what the "shorted" link does ...
Click to expand...

Good question.

Badblue: Can you tell us what the IC numbers are on this chip? (multi-colored box)

image_kittso.jpg
Click to expand...


image_biaqsz.jpg


here are a couple other close ups


image_hbkglw.jpg

image_jtewcv.jpg

image_myiava.jpg


Chablis_m said:
What kind of cell holders are these

They look to be solderless with a thread stud at each end

You are using a copper wire buss bar between the threaded studs

Are these custom made?
Click to expand...

Yes, these are custom 3D printed 38120 holders and twisted 12ga copper wire connections. I usually used aluminum bars but I ran out for this pack. I might replace them later at some point when I make more bars.
 
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