Maxing out 24 volt charge controller

sepsolman411

Many simple charge controllers say they will regulate between 12 and 24 volts from panels. If the charge controller states a maximum input of 120 watts at 8 amps, then what happens when you push 120 watts with 40 volts at 3 amps? Will the charge controller self-regulate down to 24 volts or will some fuse blow in the regulator? Also, with the 16 volt drop is it better to connect the panels in parallel rather than in series?

Cariboocoot

Re: Maxing out 24 volt charge controller

There are (mainly) two different types of charge controller.

The first is the Pulse Width Modulated (PWM) type, which functions more or less like a switch; it either connects the panel or disconnects it according to the needs of the battery in respect to the programming of the controller. In Bulk mode, the "switch" is on and whatever the panels can put out goes to the battery. In Absorb or Float modes the "switch" turns on and off, very rapidly, to maintain the preset Voltage level at the battery.

The other is the Maximum Power Point Tracking (MPPT) type. This is much more complex. It can "down convert" higher panel Voltage to proper charging Voltage at greater Amperage as needed.

Normally, the panel Voltage used with a PWM controller has the same nominal Voltage as the system, with Vmp (Voltage at Maximum Power) level designed to produce the proper charge characteristics using that type of controller. So a 12 Volt system will charge at 14.2 Volts from a "12 Volt" panel with a Vmp of 17.5.

For MPPT controllers, these numbers aren't particularly relevant. It's more along the lines of Watts in = Watts out, with the drop in Voltage translation to an increase in current. As in 140 Watts in @ 70 Volts & 2 Amps = 140 Watts out @ 14 * 10 Amps.