I am debating whether or not to get the 450/200a MPPT or just adding another 250/100a MPPT. I already have one250/100. Any suggestions?
It will relaly deoend on your needs and roof and what panels are available. And install space
The 450s need a lot of it.
MPPT 250/100 has 1 tracker for three parallel short string.
RS450/100 has two tracker for two longer strings
RS450/200 doubles the RS450/100.
With RS you need less surge protection devices (2 not 3) and may have better results on different directions due to more trackers, like east/west strings.
Over paneling with east/west strings can use the 100A-charger better.
With 450V you may fit PV panels better.
The Victron’s MPPT calculator with different panels for both MPPT/RS.
I have a 450/100 and a 250/100.
The limiting factor of the rs450 is its 4kW max limit per tracker.
The only way you can get to max 100A output is to have say 4kW on tracker 1 and 1.8kW on tracker two (or say 2900W per tracker to evenly balance. So that’s two strings coming back, two SPD600s, two 600V breakers or two string imo disconnects etc. Its basically two 450/50s.
With the 250/100 that 4kW per tracker nonsense doesnt apply. You can run say 5s3p with 41Voc panels, and run one 8AWG run back to the scc (because you’ll prob be in the 32-33A range, beyind 10AWG). You will also need some staubli branch connectors and inline fuses to protect the three parallel strings (versus combiner box with breakers etc).
With the 450/200 you have a little more flexibility because you could just use three trackers at 4kW each to get to 200A (think of it as three 450/70s), and ignore the fourth tracker.
The 250/100 is also completely silent versus the fan noise of the rs450s. No dust getting sucked into the innards etc. And it can take bare wire whereas the rs450s are limited to the mc4 models now.