EG4 - 48V System: 12V in Series vs 48V in parallel?

[mikebergy]

Just curious on your thoughts about this, or if you might point me to the right resources.

EG4 12V 400Ah batteries have a 200A BMS. EG4 48V 100Ah batteries have a 100A BMS. They both cost about the same

Are there any advantages to using 4x 12v in series? My gut feeling is to just purchase the 48V packs and wire them in parallel.
Thanks.

 

[timselectric]

If your system is 48v. Buy the right battery. (48v)

 

[Rednecktek]

Are the 12v batteries connectable in series? I understand the logic but just want to point out that going the series route requires 4x the rack space for 5kwh of storage.

If you do 2x 48v batteries you get 10kwh, 200a max draw, and takes half the space.

4x 48v batteries gets you 20kwh and 400a max draw.

 

[mikebergy]

4x 12V 400Ah would be the same number of kWh as 4x 48V 100Ah, but as you are mentioning it, if I parallel 4x 100A BMS, I will have 400A available instead of the 200A I would have by connecting 4x 200A BMS in series. It seems the better route to go with parallel connections. Thank you!

 

[mikebergy]

If your system is 48v. Buy the right battery. (48v)

I haven’t designed the system yet. You know that the both the 12V and 48V batteries both have series connections inside them, right?

I am soliciting information from folks who have working knowledge of both the series and parallel setups.

 

[timselectric]

I haven’t designed the system yet. You know that the both the 12V and 48V batteries both have series connections inside them, right?

I am soliciting information from folks who have working knowledge of both the series and parallel setups.

It's not the series cells.
It's the series BMS's.
The BMS's work independently from each other.
When in series they will drift away from each other.
Without extra equipment (battery balancer) or extra effort (taking them apart and manually balancing them). You are much better off doing it correctly.
But hey, what do I know. lol

 

[sunsurfer]

If you think you would want to switch over to a 12v(or 24v) inverter in the future or as an emergency backup, you could go 12v. Only thing is you will need a balancer to keep the batteries ballanced. Of course you would need the other pieces...SCC, etc...

Otherwise, go the 48v route.

 

[mikebergy]

If you think you would want to switch over to a 12v(or 24v) inverter in the future or as an emergency backup, you could go 12v. Only thing is you will need a balancer to keep the batteries ballanced. Of course you would need the other pieces...SCC, etc...

Otherwise, go the 48v route.

That is the one thing I wasn’t sure about, the smartness of the BMS in these types of batteries - I didn’t know if there was a way to connect them all up and have them talk to each other, or if you had to treat them as independent from one another. If there is not a way for them to communicate with each other, then it only seems advantageous if I wanted them to potentially serve a 12V system in an emergency system, thank you.

 

[sunsurfer]

That is the one thing I wasn’t sure about, the smartness of the BMS in these types of batteries - I didn’t know if there was a way to connect them all up and have them talk to each other, or if you had to treat them as independent from one another. If there is not a way for them to communicate with each other, then it only seems advantageous if I wanted them to potentially serve a 12V system in an emergency system, thank you.

I do like to have options in my systems to move stuff around and I have done it. But, there is also advantages to keep it simpler. The youtube channel "projects in paradise" did a video that was taken down on his neighbors Battle Born batteries that he had 4 in series for 48v. He had a melt down on one battery. They got out of ballance with each other in a bad way. The BMD DID NOT SHUT DOWN for over charging and some batteries where at 17volts and not disconnected.