Beginner BMS/Battery questions...

[ridgerunnersjw]

Good afternoon...
I have some basic questions that I am hoping this forum can answer. I would like to purchase 5S3P Li-Ion battery with a BMS/balancer. I have multiple applications: A) 5S3P (x3) in series for an equivalent 15S3P configuration B) 5S3P (x3) in parallel for a 5S9P configuration.....I am trying to decide whether to do a 15S BMS that is over-sized both on the voltage and current to support the requirements of the parallel configuration OR whether to embed each 5S3P as suggested with a 5S BMS. So now to my questions:

1. If I purchase the 5S3P with BMS/balancer and three in parallel of these packs in parallel to get the capacity, will the BMS/balancers in each conflict with each other? My understanding is parallel cells balance themselves out and the BMS is there to support the series cells, so my inclination is to think that the three in parallel will work??

2. If I go with a 15S BMS/balancer can I hook (3x) 5S3P (only cells here no BMS on the 5S3P's) at the bottom end of the 15S BMS and will it work (assuming of course it has been chosen to support the 9 parallel cells current charging / discharging requirements?

3. Final question, very similar to Question 2...Would I be able to build the battery packs up WITHOUT BMS and then use a single 5S BMS/balancer external to the packs to balance 5S3P (x3) in parallel if I sized it appropriately for the current for the 9 parallel cells?

I appreciate the answers
Thank you.

 

[itsmoked]

You do not want to have a bunch of BMSes working directly in parallel. So, do not have cells with a BMS paralleled directly to more cells with a different BMS.

Either:

BMS all the cells in a battery then parallel the batteries.

OR

Parallel ALL the cells and use one BMS across them all.

You can use as many BMSes as you want in series stacks of batteries.

Keith Cress
kcress -

http://www.flaminsystems.com