Wiring photovoltaic panels, a charge controller, an inverter and batteries

Introduction

Using the Renogy or another brand charge controller (as shown below), it's fairly easy to wire up your system. In fact, everything is ready and marked for this. All you need to do is ensure the polarities of what you're connecting are correct. This should be very easy for the batteries, since they're well marked and for the inverter, well marked also.

In the diagram above, the inverter is shown connected directly to the battery. The Renogy 30 Ampere controller has terminals for (as shown immediately below, from left to right) the photovoltaic panels, the batteries and the DC load including inverter, instead of connecting the inverter directly to the batteries. Electrically, it's all the same no matter which way you do it. What you must remember, however, is Renogy's strict warning: Do not connect devices such as power inverters, [...] with heavy electrical load that exceed the charge-controller's ratings.

In other words, do not connect some huge inverter whose output exceeds the charge controller's own capacity. This would not be a good idea even if you weren't connecting through the charge controller, but directly to the battery(ies).


And the polarity of the photovoltaic panels?

What might not be so obvious is the solar panel polarity. It's best not to try to find it. Instead, use this method employing a volt-ohm meter:

  1. Begin this procedure during daylight such that your panels are putting out current.

  2. Set your meter to DC Volts and a scale that will cover the output voltage of your panels (12 Volts, 24 Volts, etc.).

  3. Apply the meter leads to the cables coming down from the panels. The polarity doesn't matter as that's what we're going to determine. Having the polarity wrong will not damage your meter.

  4. If the needle (or display) deflects negatively, your polarity is wrong. Reverse the leads as they're connected to the solar-panel cables.

  5. As soon as your meter indicates the expected voltage from the panels, the cable that your red lead is touching is positive and the black lead is touching the negative cable.

  6. Mark your solar-panel cables accordingly.

Another wiring diagram, somewhat more pictorial than the one at the top of the page. It uses red for positive and black for negative. Note, however, that the two batteries are in parallel, as would be more common with a 12-Volt system. A 24-Volt system would place the two 12-Volt (or four 6-Volt) batteries in series.


Instructions for connecting the charge controller

The charge controller is the centerpiece of your solar electric system.

  1. Ensure all subsystems are installed and leads (cables, wires) handy to the charge controller.
    1. Battery or batteries
    2. Photovoltaic (solar) panels
    3. Charge controller
    4. Inverter

  2. Connect the battery according to the polarity shown on the battery and on the charge controller.

  3. Connect the photovoltaic (or solar) panels respecting the polarity. At this point, your solar panels are in the business of providing power to your battery.

  4. Connect the DC loads, probably your inverter. This is optional. You do not risk anything by not connecting a load. The charge controller will continue to top your battery off as power leaks away (through system inefficiency).

  5. Read your charge controller's instructions to understand how the system is now operating. Each controller is different though they all share a set of common functionality. Below are further instructions for the Renogy PWM 30 Ampere Charge Controller.

Renogy 30 Ampere-specific instructions

1. Once the battery is connected, the charge controller will illuminate a red light that will turn green when the voltage from the battery is in the right range.

2. Another green light will come on if there is enough sunlight.

3. An orange or red light will indicate that the battery capacity is low and the batteries need recharging. Do not connect devices to the DC load/inverter until there is enough charge as indicated.

4. An LED light is associated with each subsystem. The lights are shown in the image below (green, green and orange) left of center of the charge controller. From left to right, the lights mean:

System Description
Solar panels
Green light ON Solar power is charging the battery.
Green light BLINKING System is over voltage.
Battery
Green light ON Battery level is in the right range.
Green light SLOWLY FLASHING Battery level is full.
Orange light ON Battery level is low.
Red light ON Load has cut off.
DC load/inverter
Orange light ON Load output in service.
Red light SLOWLY FLASHING Overload; too much current drawn by load.*
Red light BLINKING Short-circuit in load.**

* Disconnect part or all of the load, that is, unplug one or all devices drawing power from the inverter. This would be a fairly common error meaning (in order of likelihood):

  1. you need to let the solar connectors recharge your battery,
  2. the solar panels aren't getting enough sunlight to recharge the battery,
  3. your system connections have deteriorated,
  4. your battery (or one or more of your batteries) have deteriorated and may need replacing
  5. your solar panels are failing,

** Disconnect immediately the inverter and/or all devices connected to it. Diagnose this problem. This will require some electrical understanding. If you've correctly connected your inverter and you're not abusing any devices by messing with them electrically, this would be an extremely uncommon error and should never happen.

A few hours after this picture was taken, the DC load/inverter light went out (from orange) and the Battery light began winking slowly indicating level full. My system works!