24/48V battery bank: 12V in series or direct 24/48V?

[deeperblue]

Hi,

I am planning the build for my RV.

When building a 24V/28V battery bank, can I build 12V banks using 12V 4S BMS and then put them in serial?
I guess using 8S/16S BMS to directly build 24V/48V is always better, but there are a couple of reasons I would like to put 12V banks in serial:

1. To build my whole system in different stages and make sure the whole system still works between different stages, initially I need the battery banks to be 12V. (or it will be a lot easier for the whole process if it is done that way)
2. Parts are easier to get (like get 12V heating pads to heat the batteries during freezing weather.
3. Individual banks are lighter, easier to move/install.

So can I use 12V 4S BMS and then put them in serial? Does all 12V BMS support serial configurations? What's the main disadvantage of doing so? What do I need to pay attention to when building such system?

And what are the good BMS brands?

A lot of questions. Thank you very much!

 

[740GLE]

All DIY 4s BMS do not support 2s or 4s configuration to make a 24 or 48v bank, so make sure you double check.

Biggest down fall is needing balancer between each 12v pack. Or you can individually top up each 12v battery as needed.

If I were to do 4s packs configured to a higher voltage I’d do 24v at thats

IMO DIY only make sense ($ and time wise) when using >280ah cells, which are decently heavy even for a 4s.

If I were to do 48v, the 100ah rack or even 50ah rack batteries are pretty movable.

 

[Wattson25]

You can totally build a 24V/28V battery bank by putting 12V packs with 4S BMS in series for your RV. It’s cool for your staged build, grabbing 12V parts like heating pads, and keeping packs light to move. Just make sure the BMS supports series setups—not all do.

Downsides? Balancing might be tricky. If one pack charges or dies faster, it can mess things up. Use same-size, same-age packs and watch your wiring—keep it tight and clean.

For BMS, JK and JBD are dope. I’m using this JK one: https://www.docanpower.com/jk-bms-200a-bluetooth-solar-lifepo4-battery. Solid pick!

 

[740GLE]

Just be sure the BMS can support 2s configs. I know my JBD 200a can’t.