I have two banks of 12v, made up in 4s4p configuration. I wish to monitor each cell, and protect each battery. Output is to be contactor controlled by the BMS.
Is the K9 suitable for this configuration? I see it has 16 inputs.
I don’t think K9s would be a great fit for your proposed configuration, they can monitor a string of cells between 3S and 16S, and you need more K9s for more strings. In other words, you can’t have the voltages in the K9 go 0V, 4V, 8V, 12V, 0V, 4V etc. as there is a negative difference that will damage the K9.
Instead you could consider:
Paralleling up cells into groups of 4, then 4 in series, and monitor that 4S string with a K9
Moving to a higher pack voltage i.e. 16S for 51.2V
What are your thoughts on the above? Could you tell us a bit more about how you will be using the pack?
Have the same id. Want a 12v pack 1.120ah. And monitor each cell individually. So 4 cells in series. And 4 packs of 280ah 12v. And then the 4 packs parallel.
Of course I can make 4 individual packs witch each a own bms. But in mine opinion it is more safe to do it with one bms.
We refer to the configuration above as “Multi-String”, and yes it would need 4 K9s to manage it. If these are new cells that are well matched, I would instead advise you to parallel them first, then place those blocks in series. This would allow you to use 1 K9 and reduce cost.
If you want to take your current approach you can. It has the minor advantage of watching each cell individually, so if one has a problem you may notice it sooner.
You will need BlockMons to do this (they are independent for each cell and such there are no negative voltages).