Wednesday, Nov 23, 2011 at 22:58
no worries, the link works ok.
The giveaway can be seen in the specs:
Max PV open circuit voltage: 29V for 12V battery, 65V for 24V battery
What this tells you is that the ratio input voltage/battery voltage is fixed.
You can't use a 24V rated panel (which has an open circuit voltage of about 42V) without losing MPPT functionality, in connection with a 12V battery.
This controller belongs to a class of half baked MPPT units whose algorithm has been designed to run on cheap microcontrollers which lack the number crunching ability to perform true MPPT.
Second thing:
it mentions 3-stage charging.
But it doesn't mention the absorption-float switch over condition.
This is important because if it doesn't switch over when the battery is almost fully charged it'll cause dry out over time. And if it switches over too early, the symptoms of under-charging are slow capacity loss.
And it definitely can't do cumulative absorption charging which is the most battery friendly algorithm for regulators with concurrent loads during charging.
There's no battery temperature sensor either.
Measuring the temperature inside the unit is a cheap and crappy way, because the units can heat up significantly during operation.
E.g. we've tested the internal temperature rise on a 10A MPPT regulator at full current to be 25 degrees. In connection with a temperature compensation coefficient of -24mV/degree, that results in a -0.6V deviation from the rated charging end voltage.
You decide if this unit is worth the dough.
cheers, Peter
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