I am just about to start purchasing my components for my house install, non ESS.
I have already purchased my battery, a Fogstar 32KW/h 48v unit, and am now ready to install my panels. I’m intending to purchase 16 510w Trina panels. 8 will be south facing and the other 8 will be north facing. Not ideal but its what I have to work with at present.
The panels will be connected on the south side - 4 in series, 2 strings paralleled together and same again on the north side.
With this orientation/connection could I use a single RS 450/200 MC4 4 tracker unit or should I use 4 independent MPPTs or even 2 MPPTs, one for the south side arrangement and one for the north side arrangement?
I’m concerned the north side that wont be a good producer during the winter months may effect the RS overall performance?
The panel VOC is 40.6v, Isc is 15.93A and power is 510W
Eventually this will be tied into a Victron 10kw multiplus 2 inverter supplying the whole house. It will not be tied into the grid but will have a dedicated grid single supply to a stand alone battery charger so during off peak hours the battery can be charged by the grid if required during the winter months as I dont believe my limited solar set up will keep me running during the few winter months.
Many thanks for any help
OGPS
(Ed @ Off-Grid Power Systems - offgridps.com)
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The SmartSolar MPPT RS 450/200 has four independent trackers (channels). If one tracker is degraded it won’t affect the others. Compare price and whether or not you want any single points of failure and then decide.
The 250/60 is not isolated, so you will also need ground fault detection. The 450/100 and 450/200 are galvanically isolated.
I have a 450/100 with East and West arrays. The trackers are independent and have reverse image curves, but the yield is symmetric. This is the best way to configure them if you can, to avoid clipping.
There are several ways to get “clipped” throttled in a solar power system. If you don’t size the production and usage correctly, you can experience throttling when the system fills up. A battery with a charge current limit may reduce the current, and if all the solar arrays are producing more than what the MPPT can handle, you will also be throttled. Additionally, if your inverter is undersized, you won’t be able to fully utilise the solar energy generated by the MPPT.
Since I am grid-tied, I have options for handling excess power: I can either export it or use it. I try to utilise 50% of the energy at night; otherwise, I can’t use it during the day. My export limit per phase is 5,000W, which can easily be exceeded with another grid-tied PV inverter on the same phase. The 5000VA multi-inverter can only export up to 4,500W, so there’s no need for more solar. Furthermore, the battery can handle a maximum charge of 100A before it starts to overheat. On a sunny day, I can fully charge the battery from 0% to 100% without any issues.
The lopsided energy production curves from the east-west orientation of my panels allow me to collect more energy in the morning and afternoon, rather than having an excess in the middle of the day.
I’ve had another go on the Victron calculator and decided on two 250/60 MPPTs. One for the south side and one for the north side.
I think this gives me better redundancy/options if one goes down and it’s a hell of a lot cheaper than an RS.
The calculator gives a PV power ratio of 114% which is in green so I guess this is good news? It does seem to suggest it will throttle at extreme temps but where I am in France I never expect those temps…
If you want redundancy, consider getting two 450/100 units. You won’t regret spending a bit more, as they are in a different league. They simply work well, and their smaller cable size, higher voltage capability, shade-tolerant algorithm, and active cooling ensure that you won’t encounter any issues. Additionally, they are galvanically isolated, so you don’t have to worry about dangerous high-voltage DC on the battery side.
I guess you will have to be creative about this. Without ESS, charging schedules are not built in.
The figure of 114% means your panels will have capacity to produce 14% more power. Up to 30% is ok. As you are unlikely to actually ever see full panel capacity, over-paneling is good, especially in winter.
By the way, I have 4 strings on two 250/100s without an issue.
I do have a rudimentary charging schedule in that in France our energy supplier sends a signal down the line, during off-peak hours, which throws a relay energizing, for example, our hot water cylinder.
My intention is to employ this to power my stand alone battery charger so during the off-peak hours it gets topped up automatically overnight.
Good call, as the rs450s have an effective 18A limit per tracker (can go above but no reverse polarity hookup protection), you would have been well over with two parallel strings of 15.93A.
