Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
BMS on BMS
#1
I have (280 qty) LiPo 7.4v 2S w/BMS modules.  I am wondering if it is advisable to put these in a 40P7S configuration with a 7S BMS on top "OR" break each 2S pack apart and remove the module level BMS then do a 3.7v 80PS7 config with a 7S BMS?  I'm a beginner and have been trying to learn from all you folks, but I've not been able to find anything about BMS on BMS interactions.  I'm attempting to make a portable solar generator.  Any help would be greatly appreciated!
Reply
#2
7s40p

Should be fine to do. Basically the 2s modules would be like fuses, to a degree, isolating in case of an issue.

Interesting arrangement though. I'm guessing you would take 20 of the 2s packs and parallel their output. Then take 7 of these packs and string them together in series. Correct?

If this is so, then the fuse example would be further more accurate as it being like an internal breaker that can be reset. So if 1 2s pack goes bad and the bms shuts off, and then the other hit an overcurrent limit, the'd be triggered to turn off, instead of blowing a fuse that'd need to be replaced. Might save work down the road in case of an issue.

Can you provide pictures of these? Also, have you read the FAQ?
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#3
(10-14-2020, 08:48 PM)Korishan Wrote: Thank you so much for the quick response.  I got these from BatteryHookup a few weeks ago for $2.20 each.  I did look at the FAQ when I joined back a while ago.  From your reply, I'm feeling a little better now about put this generator together.  The only other thing I'm a little worried about is the LiPo chemistry of the these batteries

Interesting arrangement though. I'm guessing you would take 20 of the 2s packs and parallel their output. Then take 7 of these packs and string them together in series. Correct?  CORRECT

Korishan

I didn't see the "7s40p" you posted at the top until after I had posted.  Thanks for the correction.  I always thought putting the "S" first was odd, considering we always build capacity packs in parallel and then in series for target voltage.  But, I get the standard.  Thank you again!

(10-14-2020, 08:36 PM)Regrdb Wrote: I have (280 qty) LiPo 7.4v 2S w/BMS modules.  I am wondering if it is advisable to put these in a 40P7S configuration with a 7S BMS on top "OR" break each 2S pack apart and remove the module level BMS then do a 3.7v 80PS7 config with a 7S BMS?  I'm a beginner and have been trying to learn from all you folks, but I've not been able to find anything about BMS on BMS interactions.  I'm attempting to make a portable solar generator.  Any help would be greatly appreciated!

I should have said a 3.7v 14s80p config with a 14S BMS, if I broke these apart.  The target voltage is 48v to 52v.
Reply
#4
Yes you will need a 14s BMS not a 7s BMS.
You will need connections from the middle of each 2s pack.
LiPo is a more volatile chemistry so be careful with charging correctly, pack temperatures, etc & consider having a steel case for it.
Running off solar, DIY & electronics fan :-)
Reply
#5
(10-15-2020, 02:37 AM)Redpacket Wrote: Yes you will need a 14s BMS not a 7s BMS.
You will need connections from the middle of each 2s pack.
LiPo is a more volatile chemistry so be careful with charging correctly, pack temperatures, etc & consider having a steel case for it.

Thank you [b]Redpacket.  I'm not sure how I would alter the packs current configuration, as they already have a BMS.  Each pack is in a steel case already and stack very well, but a larger steel case for each 40p pack is a good idea. [/b]
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)