Hello; After calculating my Daily energy requirements in watthours, I found out that my system is required to generate 11A. I am planning to configure my batteries 2pcs of 150Ah/12 connect them in series to make a 24V..I am also planning to use 4 solar panels 12V/100watts( connected 2S2P) and connect a victron mppt controller 75/15, Kindly advice me if I am correct
If that works depends on the specs of the panels open circuit voltage.… and so on. Those values need to be below the specification of the MPPT. If you share the info on your panel and the minimum temp in winter someone might be able bro help you.
Or you download the excel chart from Victron to size your MPPT, here you can put in all the values and it tells you which mppt suits your application.
I would personally recommend to oversize the MPPT in case you have space for more panels, in case you want to add two panels in the future. I had to buy several times a new mppt cause my energy need extended the capabilitys of the Unit.
I am curious to see the informed answer. This is only my understanding as a user.
You are good.
Two things I have learned:
1) No panel puts out it's full wattage outside of the lab. Less if it's a flexible panel. Closest would be a cold day at altitude.
2) The beauty of the MPPT is that it will current limit if over powered. So when it's sunny, you will be limited to 15 amps and you might say, "wasted energy due to limits" but it's not a problem otherwise and peak hours are only part of the day. And having those extra watts of panel will really work for you when sunshine is off-peak as panels may output half or less of rated. So, 400 watts of panel (@12v) will only get you 15 amps at noon, but you will be still be pulling 10-15 amps in cloudy and off-peak hours.
Thus even a somewhat "undersized" MPPT can still be fine in use, especially in situations where sunlight is often or usually reduced. I get irritated when somebody adds extra capacity to the specs for an MPPT charger. You don't need it because your panels are not giving full rated and then the MPPT will just dump excess if the panels do hit it's limits now and then.
That said, your 75/15 would be seriously undersized if charging a 12v battery bank and not 24.
To 1) I often get 205W from two 100Wpanel in series…
To 2) of cause you can connect more panels, but therefore you risk warranty coverage and you loose potential energy. If you want you can do the math whats better, to chop of 20-30% of your peak power, therefore spend more money on panels or to spent more on a MPPT therefore save by buying only the panels necessary…
with your solar panel Imp - Vmp - vco - Ico information use the link below
