Im so confused building a power wall and need help!

[Soundwav]

Have a few (6) 7s 20p (18650) batteries that i have built over the last few days using batteryhookup nickel fuse with spot welding.
finally got my bms's in the mail and wired up last night, easy enough i think?

now my issue is if i check the voltage at the xt60 (Bms) connector i get 18.6v.
These are to be 24v batteries.
if i check voltage directly at the battery i get 26.2v (good?)
if i check voltage at the other side of the battery directly i get 17.6v

ive tested each cell over and over again and each cell is at storage mode of 3.7v. I put the cells in storage mode as i tested each cell using 2 xtar vc8 chargers,
took me months as i have thousands of 18650 cells.
Im going to look over the entire battery AGAIN!! tonight.
Im missing something or i dont understand WTF im doing and quit before i burn the house down!

another question i have is do i need to connect the negative of the bms to each cell?? or can i connect it to one cell as they are all connected with the nickel strip?

 

[sunshine_eggo]

Have a few (6) 7s 20p (18650) batteries that i have built over the last few days using batteryhookup nickel fuse with spot welding.
finally got my bms's in the mail and wired up last night, easy enough i think?

BMS may be inactive and requires reset. What BMS?

now my issue is if i check the voltage at the xt60 (Bms) connector i get 18.6v.
These are to be 24v batteries.
if i check voltage directly at the battery i get 26.2v (good?)

3.7V * 7 = 25.9V probably fine.

if i check voltage at the other side of the battery directly i get 17.6v

"other side of the battery"?

ive tested each cell over and over again and each cell is at storage mode of 3.7v. I put the cells in storage mode as i tested each cell using 2 xtar vc8 chargers,
took me months as i have thousands of 18650 cells.
Im going to look over the entire battery AGAIN!! tonight.
Im missing something or i dont understand WTF im doing and quit before i burn the house down!

another question i have is do i need to connect the negative of the bms to each cell?? or can i connect it to one cell as they are all connected with the nickel strip?

when you parallel multiple cells together, you essentially have one cell. Connection to a single point should suffice.

 

[Soundwav]

BMS may be inactive and requires reset. What BMS?

daly bms/amazon bms

"other side of the battery"?

+- on one side of battery gives 26v
+- on other side gives 17.6v

ill have to upload a picture so you guys can see what i mean

 

[sunshine_eggo]

daly bms/amazon bms



+- on one side of battery gives 26v
+- on other side gives 17.6v

ill have to upload a picture so you guys can see what i mean

Do you mean other side of BMS?

 

[Soundwav]

One sec I'm going to try and upload a pic

 

[Soundwav]

Hope this explains it better??

The Amazon bms is new out the box and the daly bms is used..

Both batteries I've built have the exact same issue

 

[Soundwav]

Upon further inspection the Amazon bms is fried!!!

Like completely toast!!!!!

I did something wrong

 

[Soundwav]

I think I need to connect my wires differently?

 

[sunshine_eggo]

Hope this explains it better??

The Amazon bms is new out the box and the daly bms is used..

Both batteries I've built have the exact same issue

You're not measuring the "other side of the battery". You're just measuring it in a way that leaves out the last two cells - one on each end.

26.2V - 3.7V - 3.7V = 18.8V

Upon further inspection the Amazon bms is fried!!!

Like completely toast!!!!!

I did something wrong

Certainly agree that something is wrong.

I think I need to connect my wires differently?

Possibly. You're leaving a cell out by measuring only the top:



Assuming the cells are in series like this or the reverse direction.

 

[J.P.]

Have a few (6) 7s 20p (18650) batteries that i have built over the last few days using batteryhookup nickel fuse with spot welding.
finally got my bms's in the mail and wired up last night, easy enough i think?

now my issue is if i check the voltage at the xt60 (Bms) connector i get 18.6v.
These are to be 24v batteries.
if i check voltage directly at the battery i get 26.2v (good?)
if i check voltage at the other side of the battery directly i get 17.6v

ive tested each cell over and over again and each cell is at storage mode of 3.7v. I put the cells in storage mode as i tested each cell using 2 xtar vc8 chargers,
took me months as i have thousands of 18650 cells.
Im going to look over the entire battery AGAIN!! tonight.
Im missing something or i dont understand WTF im doing and quit before i burn the house down!

another question i have is do i need to connect the negative of the bms to each cell?? or can i connect it to one cell as they are all connected with the nickel strip?

OK, I have built similar battery packs out of 18650 cells and you have a few issues.

1. For sure. You need bus bars on those packs. One should run down the entire length of the main positive nickel strip and the other down the main negative length. They should be soldered in several places. You can't just connect to the end battery and expect that thin nickel strip to handle all the amps that pack can produce. See these links to get an idea of how to make and solder on the bus bars.

2. In My Opinion. Your BMS's are WAY too small. They are only 20 Amps. Each on of those cells has the potential for 10 amps and those 20P packs can produce 200A. I would recommend 100A BMS's but I do not know what you are trying to use them for.

3. The poster above addressed you are not measuring your battery at the MAIN Positive and MAIN negative so you are not getting the correct pack voltage. Make sure when you put the bus bars on that you put them on the single rows of nickel strips on each end of the pack. One will be on one side of the pack and the other will be on the other side of the pack. Top and bottom... so to speak.

 

[Soundwav]

Thanks for the help guys.

I'll watch the videos when I get home from work