1
\$\begingroup\$

Recently I bought cheap a lot of CASIO DT-9723LI battery packs.

Every pack consists of 2 Sony 6th-gen Li-ion 18650 cells and its own 2s BMS. Here the question arises: Can I connect this packs parallel and series simultaneously?

My desired pack must be 6s (so 3 Casio battery packs in series) and 9p (9 Casio battery packs in parallel). I know that I could take out the cells and build a new pack with its own new 6s BMS, but that is a lot of work. On the "old" BMS PCB (from the Casio battery packs) I found two TPCS8208 Field Effect Transistor and one S8232A Battery Protection IC. Maybe it will help.

\$\endgroup\$
  • \$\begingroup\$ if you take out the cells and do not exactly know how to connect to BMS, you risk ruining the cells. With Lithium, a very flammable metal, ruining a cell means high risk of fire and explosion. A passenger plane already went down this way. I would not even think of doing what you described. \$\endgroup\$ – Roland Nov 4 at 0:08
0
\$\begingroup\$

It depends, but generally, no except for testing.

BMCs tend to switch off the battery when over-charged, over-loaded, over-discharged, over-heated or when it just feels like to.

Think about over-discharging: you will never get them to switch off together. The first one switching off in a parallel pack will transfer the load to it's peers, eventually overloading them. The first parallel pack to turn off will get all the voltage of the other two packs in reverse. Will it survive?

Then, charging is another sad story. I don't know if s8232A tries to ballance the cells, but if it does, every one of them will ballance just the cells it is connected to - and by doing so, it will load it's parallel peers down from ballance with their serial counterparts. Completely counter-productive.

Some BMS modules can be chained together in order to function as one large BMS. They generally need external connections and generally, external logic. s8232A is not one of them.

p.s. I checked - there is no ballance logic in s8232A. But still no happines at other points.

\$\endgroup\$
0
\$\begingroup\$

It is better to take the packs apart. Gently cut of the nickel strips. Resolder them into one pack! The operating voltage of a single li ion cell for a long life runs from 3.1v to 4v Make sure when you connect your cells your charger wont't overcharge. If you have four cells in series, your charger must not be higher than 15.8v dc to be at the save side. Get a cheap chinesium bms that will cut of at 12.4v. For balancing your cells make a cheap resistor board, use this only for top balancing. So they will basically burn off extra energy above 4 volt(exact 4.1). With li ion you MUST protect overvoltage and undervoltage, for reasons mentioned before. Dont ignore this, your house wont be the first one

\$\endgroup\$
  • \$\begingroup\$ Two days after my question I took those packs and solder them into 6s9p pack. Today I have made a plan in AutoCad of housing with switches, fuse and usb qc.3.0 module. My electronic dealer has run out of 6s bms so I have to wait till restock. I will be charging it with my B6mini balance charger. Maybe tommorow i will cut housing panels from 8mm hard MDF. If you want updates of my "little" project just let me know. \$\endgroup\$ – Skarpeta Nov 11 at 15:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.