How many BMS's for a 13S13P

[Terk]

Hello: I'm a newbie, but I have lots of high quality Samsung and Sanyo cells and esential equipment. The first battery pack I'm constructing is a 13S13P for a 48v 26Ah pack. My question is how do I integrate the BMS? Is it attached to only one 13S1P at a time when charging or can I charge the entire pack at once? Do I need to have 13 of the 13S capacity BMS's connected in parallel? Thank you for your consideration.
Terk

 

[dnmun]

if it is 13 wide the you would build 13 individual 13S packs by linking the cells end to end through a small serial link.

then mount the batteries together and connect them in parallel by soldering the parallel connecting wire to the middle of the links.

then connect the BMS sense wire to the parallel link so that now the entire pack would be 13S13P. and one BMS.

 

[Terk]

Thank you. I was thinking along those lines too, but just wasn't totally sure. I also see the need, from time to time, to possibly take the pack apart to check on individual cells in series to see if they are in all equally within parameters. I'm using brand new cells and will have a lot of less worries than somebody recycling cells and will most likely not need to replace any. But when using 169 cells in a pack, all it takes is for just one to go bad and cause a cascading effect.
Terk

 

[dnmun]

it is really almost impossible to take a large pack apart after it is assembled. you need to balance all of the cans used in the pack initially before you build the battery up.

if the cans are connected in parallel first then it requires removing that entire parallel set of cans and then disassembling them so you can find the one that is self discharging.

if the pack is built by connecting all 13 of the 13S packs together in parallel then they can be disconnected from each other at the parallel links and then the can with high self discharge can be isolated and removed more easily.

 

[Terk]

I'LL be using an IMAX B6AC to check the cells. There should be little variation from cell to cell because they are new Samsungs and never have been used. Connectors will be used to make the pack modular whereas each 13S can be easily disconnected from one another and each of the 13S tested. By having 14 wires connected to each 13S, individual cells can then also be checked, if a particular 13S has an irregular voltage reading. I'm thinking about connectors having 14 female slots attached to a ribbon wire that has one wire going to each cell of a 13S. It will be easy then to check not only the entire 13S, but any specific cell in each 13S. That way, the battery pack can be easily broken down into 13 pieces and each cell of each 13S can be checked with a multimeter. Do you think that is feasible?

 

[dnmun]

to isolate a bad can or pouch in the middle of a large battery you have to isolate the battery in sections using a binary search as you focus on finding the string with the bad cell.

if you know your problem is in channel 6 of a 13S pack then you have to separate the battery in sections beginning at channel 6 all the way up through 13 and the common B+ current collector has to be split so that the two sides are not connected in any way above the bad channel.

you have to continue the binary search until you have the row isolated with the self discharging cell. i had to pull 8 bad pouches from all throughout the middle of a 21S3P 8Ah nanotech pack.

 

[Terk]

I'm going to take pics of the project from beginning to completion and post them on this forum, along with a narrative for each pic.