*****My Apologies. This is long, but I wanted to try and get all of my questions in one post/thread*****
Since it seems TopperHarley and Bluerso and I are all building the about same thing(My trailer is 50A as well), I though I would run some # past all of you to see if I am also on the right track.
The basics...
I am using basically the same 50A system diagram so getting the parts and the physical build is not hard, but since all of the diagrams assume you are going to use "drop-in" batteries (Battleborne, Dakota Lithium, etc.) none of them touch on the DIY battery build itself, and even Will is a little vague on BMS sizing. My questions are pretty much the same as topper's original BMS and fuse question, but what I really need is for someone to validate my math and recommend a really good BMS(I won't use a Daly unless I have no other option) from a trusted source, and confirm my choice of master fuse.
PERTINANT EQUIPMENT
A. BATTERY BANK - 16 Prism. Cells @ 272(280)Ah each, arranged 2P4S2P (2 cells in para(6v-544Ah) then 4 pairs in series = 1 x 4s "Battery" at 12v-544Ah) then 2 x 4s "Batteries" in para for a 12v-1088Ah battery Bank. (We are boondocking and this is the size we need to run our A/C (assuming no gennie). I am not running a 24V system 'cuz I already bought the 12V MPII and I am not changing it now). For the record...I understand wire size/runs very well. This is doable in my trailer. Everything will be within 2-3 feet except for the solar panels of course)
Q1 - Can someone please check my interpretation of the attached battery spec sheet
C rating = 1C = 272A
Cell nom V =3.2v
Cell Max V = 3.65v (100% fully charged)
Cell Min V = 2.5v (0% or 100% fully discharged)
Max Discharge rate = 1C = 272A continuous or @ 2C(544A) for 60 Seconds
Max Charge rate = 1C = 272A continuous or @ 2C(544A) for 60 Seconds
Q2 - Given that the C rate for each individual cell is 272A(= to available Ah) @ 12V, and in this configuration my bank has 1088Ah, theoretically would the C rate for my entire bank be 1088A?? In other words, THEORETICALLY (I know it is not possible to do this, but just for my understanding of scientific laws) the entire bank could be charged at 1088A because the charge amperage would be equal to the available Ah in the entire bank?
Q3 - So If the actual charge input charge voltage is say 120A(max for MP II), and that 120A is divided equally between the # of batteries in the bank (ie. in my case 60A/battery) I would be well within the C rating for each cell. Correct?
B. INVERTER/CHARGER - Victron MP II 12/3000/120-50 2x120V (I got it through Continuous Resources LLC. I got lucky and got the last one on their 1st order. The have more coming in early June, but there is a waiting list)
If I assume 3000W (actual 2600) continuous, that would mean the draw on the battery bank when the inverter is in full use would be as high as 250A continuous (3000W/12V = 250A).
C. GENERATOR Parallel Honda EU2200i @ 4400A(3600 continuous) which goes through the shore power inlet through the MP II so it is not in addition to, but is the same 120A charging as the MP II charger).
D. SOLAR - I will eventually have 2,100W(6 x 350W panels) of Solar on the roof going through a set of Victron 150/45 MPPTs, so another potential 90 charging amps (2 x 45A).
CONCLUSIONS
Given that my max potential battery bank draw is 250A(as limited by the 3000W inverter) equally split by 2 "batteries" @ 125A draw each
and my max charging input potential is 210A (120 from MP II + 90 from Solar) which is well below the 1C rate for any single cell.
Therefore the max output drives my choice of BMS size as well as the fuse.
Q4 - I wonder if I should go with a 300A BMS x 2 (one on each 2p4s (8 cell) battery). That way the two batteries will split the load at 125A apiece(@<50% load) or either one could handle the entire load (should it be required to take one of the two batteries off line.), and it can easily handle any load spikes up to 600A for < 60 seconds (2C rate)
Q5 - Given the math, wouldn't a 300A main fuse be enough as well?
I look forward to all of your comments.
Thanks,
AJ
www.gregsmarinewiresupply.com
