37.5 volt panel with 48 volt MPPT

esox · May 2014

I am currently looking at some 37.5 volt 255 watt panels. Price is currently very good. Would be using for battery backup & "camping off grid". In UK can only seem to find 24v or 48v mppt charge controllers.

Without paying a fortune for a controller which seem to accept a voltage range, would there be damage to a 24v MPPT or if I got a 48v MPPT are they liable to have a minimum input voltage to work and would 37.5v not be enough?.

Many thanks for any advice.

Cariboocoot · May 2014

Re: 37.5 volt panel with 48 volt MPPT

Welcome to the forum.

You're a bit confused as to what the Voltages mean. An MPPT charge controller will be able to charge various system Voltages which may be 12, 24, or 48. The input Voltage is not dependent on this other than needing to be above the minimum Vmp for the system. As such the Vmp of the panel may be 37.5 and it will charge a 24 or 12 Volt system just fine. If the controllers you are looking at do not have specs about maximum input Voltage avoid them as they are probably not true MPPT controllers.

Otherwise you are looking at PWM controllers which work mainly on a basis of current but do require sufficient Vmp to charge the system. With one of those a panel Vmp of 37.5 will work fine on a 24 Volt system but will waste about half its power on a 12 Volt system.

Some controllers (such as Blue Sky) have even further limitations and are best avoided.

Look over the specs on some of the controllers our host carries and you'll see what I mean. http://www.solar-electric.com/chco.html

westbranch · May 2014

Re: 37.5 volt panel with 48 volt MPPT

Welcome, those MPPT charge controllers voltages you mention are their output and will most likely take input voltages as high as 72 or 96 volts. MPPT down converts to the battery bank voltage as you set.

hth

37.5 volt panel with 48 volt MPPT

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