MPPT Controllers
As I continue the learning curve, I'm finding the answers I get always lead to 2 more questions... funny how that is... I've been working backwards in developing my solar needs, going from panels t...
Forum Discussion
obiwancanoli,
I would get a larger amperage controller. Why buy more than you need? Large amperage controllers "stack" the active components. A 60 amp controller typically has 3 20 amp devices. As the solar harvest starts "low" in the morning, on a 60 amp controller, only 1/3 is active. That means it runs more efficiently and more amp-hours get stored. then at solar noon the input wattage is shared between all three segments--allowing each one to run below maximum capacity. In a 50 amp controller there may only be 2 25 amp devices. So at solar noon they won't be as efficient as the 60 amp controller. These are NOT real numbers--they are just to give you the gist of what happens.
I, too, would highly recommend the Victron controllers. Just get the biggest one that you can afford. It is going to be the most expensive component, so then adding more panels is cheap to do.
Sizing should be 125% of the maximum harvest. So for a 20 amp harvest--the controller needs to be 25 amps. The reason for this is partly "cloud" effect. Essentially the clouds may act as a lens and temporarily increase solar irradiance.
About the only mistake I made was to have a controller that does not have enough capacity to add more wattage. This means, if I wish to add more panels--I have to buy an EXPENSIVE controller. My current system panels cost $5.50 per watt, in 2005. Now it is sometimes possible to find them for $0.50 cents per watt. The first system I had was from 1992. It was 30 watts. Cost was $56.67 per watt.
Do you know how many watts-hours you will be consuming?
I would get a larger amperage controller. Why buy more than you need? Large amperage controllers "stack" the active components. A 60 amp controller typically has 3 20 amp devices. As the solar harvest starts "low" in the morning, on a 60 amp controller, only 1/3 is active. That means it runs more efficiently and more amp-hours get stored. then at solar noon the input wattage is shared between all three segments--allowing each one to run below maximum capacity. In a 50 amp controller there may only be 2 25 amp devices. So at solar noon they won't be as efficient as the 60 amp controller. These are NOT real numbers--they are just to give you the gist of what happens.
I, too, would highly recommend the Victron controllers. Just get the biggest one that you can afford. It is going to be the most expensive component, so then adding more panels is cheap to do.
Sizing should be 125% of the maximum harvest. So for a 20 amp harvest--the controller needs to be 25 amps. The reason for this is partly "cloud" effect. Essentially the clouds may act as a lens and temporarily increase solar irradiance.
About the only mistake I made was to have a controller that does not have enough capacity to add more wattage. This means, if I wish to add more panels--I have to buy an EXPENSIVE controller. My current system panels cost $5.50 per watt, in 2005. Now it is sometimes possible to find them for $0.50 cents per watt. The first system I had was from 1992. It was 30 watts. Cost was $56.67 per watt.
Do you know how many watts-hours you will be consuming?
