Connecting 8 50ah cells to bms for 100ah 12v battery

[Captain Hook]

I have a weize 100ah 12v lifepo4.
It is 2 sets of 50ah cells.
I want to install a jbd smart bms to them like my AOLITHIUM 100ah has because of the ability to monitor and adjust with the Overkill app. I am a marine electrician but not clear on this procedure. ?

 

[Rocketman]

It will not be difficult.
1. Charge each cell to a full top balanced state.
2. Take 2 cells and connect in parallel (pos to pos and neg to neg) to create a super cell - make 4 supercells. Mark with red &black markers the pos and neg terminals - maybe label them cell1a & cell1b…
3. Take the four supercells and connect in series to make a 12v battery. Pos of one supercell to neg of another supercell.

4. wire the bms up. Think of each supercell as just one cell in the bms instructions.

Did that make sense and did I answer your question- or did I miss it?

Good Luck

 

[OffGridForGood]

I have a weize 100ah 12v lifepo4.
It is 2 sets of 50ah cells.

I assume this means you have opened the plastic case, and have access to the interior...and since it was already 12v it is already set up in cell pairs(?) as described by Rocketman above.

I want to install a jbd smart bms to them like my AOLITHIUM 100ah has because of the ability to monitor and adjust with the Overkill app.

This would mean removal of the original BMS and swapping in the JBD - which you will buy separately, then confirm the BMS sense wires - not all the BMS's use the same pin-out clips, or even in the same order, so check and be sure you have the right neg, sense 2, 3,4 pos.

I am a marine electrician but not clear on this procedure. ?

you definitely have the required skills then.
My only thought on this set up: I am not a fan of monitoring pairs of cells, there is a chance of one of the pair being out of spec without the BMS 'seeing' this. That said, you already have a 100Ah pack, and it would be best to pair it with another 100Ah pack.

 

[Captain Hook]

It will not be difficult.
1. Charge each cell to a full top balanced state.
2. Take 2 cells and connect in parallel (pos to pos and neg to neg) to create a super cell - make 4 supercells. Mark with red &black markers the pos and neg terminals - maybe label them cell1a & cell1b…
3. Take the four supercells and connect in series to make a 12v battery. Pos of one supercell to neg of another supercell.

4. wire the bms up. Think of each supercell as just one

It will not be difficult.
1. Charge each cell to a full top balanced state.
2. Take 2 cells and connect in parallel (pos to pos and neg to neg) to create a super cell - make 4 supercells. Mark with red &black markers the pos and neg terminals - maybe label them cell1a & cell1b…
3. Take the four supercells and connect in series to make a 12v battery. Pos of one supercell to neg of another supercell.

4. wire the bms up. Think of each supercell as just one cell in the bms instructions.

Did that make sense and did I answer your question- or did I miss it?

Good

cell in the bms instructions.

Did that make sense and did I answer your question- or did I miss it?

Good Luck

Thanks that answers for a 4s bms. I was hoping I could use a 8s for monitoring each cell.

 

[Rocketman]

Nope - 8s will get you a 24v battery.

 

[OffGridForGood]

With the cells paired up with bus bars, they should remain close. It is just not my favourite set up, since I like to see the individual cell voltages, and know the BMS is keeping them correctly balanced.
More important, your existing AOlithium is 100Ah and will be best set in parallel with another 100Ah pack, so they share current equally and remain (close) to same SOC up and down the charge discharge cycles.
Nothing wrong with just trying it out, and see how it goes.

 

[Captain Hook]

Thanks for the input. I am still pissed they ran out of 100ah smart batteries for 200.00. I am going to make 2 50ah for other use on my boat and buy another battery for pairing.

 

[OffGridForGood]

I am going to make 2 50ah for other use on my boat

Marine application: you will want to be extra careful about water, (salt?) connections, corrosion protection.
I am no expert on marine batteries, but know enough to draw your attention to this issue.