Wednesday, Jan 18, 2012 at 08:13
The solar regulator inside the D250S dual isn't a true MPPT one.
E.g. you can't use a 24V panel for charging a 12V battery with it.
A true MPPT solar regulator is designed to track the maximum power voltage over a wide range e.g. 15~100V.
The maximum power point voltage of a panel depends on the amount of cells in the panels and operating temperature (which is also dependent on the amount of insolation).
A true MPPT regulator seeks and holds this voltage in short intervals, typically every 5 to 10 seconds.
For the D250S dual, chances are that it fixes the max power input voltage to around 17V, without actually tracking it.
Actually that makes sense in a way, because if you use a 12V rated panel for 12V battery charging, there isn't much to track in terms of max power, espcecially under hot conditions.
The advantage of true MPPT functionality is lost in the D250S, alone due to its inability to work with higher panel voltages.
Another major shortcoming of the D250S, and probably also the D250S dual is, that the battery can easily get over-charged because the absorption/float switch over is set to 12 hours, or 0.4A.
So whenever you've got a load (fridge) connected to the battery, it basically never switches back to float as long you're driving.
You could say that this manufacturer skimps on processing power of the inbuilt microcontroller, which hasn't got the muscle to run a proper MPPT routine, nor can it do cumulative absorption stage charging, nor a display.
cheers, Peter
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