Hi all
AC200MAX
i cant get my head around this, solar input max 900w
max array is 145v at max 15 amp = 2175w
why would they allow the system to take 2175W only to reduce it down to 900w
or am i missing something here
The first consideration - A MPPT solar controller has 2 processes, its input limit and its output limit. To take the second point first, this is the safe charging power for the battery bank it is charging. In the case of the 200MAX, this is 900W.
The first point re input is a combination of V & A limits as a means of converting variable inputs to provide that output limit. This relates to solar panel Watts and a combination of parallel and series connections to arrive at an output total.
In the case of the 200MAX, this allows for a large variation of solar panel combinations to get to a sweet spot of that input, which can exceed 900W input. This means trying to input 2175W is somewhat of a waste as 1275W is getting absorbed by the controller and not charging.
A worst case scenario is very bad weather in winter, i.e. my home solar outputs around 4.9kW in summer, in winter I see 1.5kW on bad days. That’s 30% of summer output and tells me that a solar array needs to be 3 times bigger than the needed output to cover that scenario.
In your circumstance, I would be very happy with the array I have. 
Of course, never exceed the 145Voc input, that will damage the MPPT.
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As an aside and to compare - My AC180 has a 500W limit at 12 to 60V and 10A.
Multiplying V x A = 600W, which is more than the 500W limit, but nowhere near the range flexibility of the 200MAX.
This limits solar panel size choices, especially the lower voltage and current limits. A nominal 24V solar panel has a Voc of around 45V, which is only 75% of the limit. Two panels in Series exceeds the Voc Max of 60V, so rarely is 500W achieved. This also markedly reduces winter inputs.
ok thanks for that, that now makes sence of it