What Charge Controller Size Do I Need For 1000 Watt Solar Panel?

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Installing a 1000 watt solar array is becoming commonplace as prices continue to drop. Now the question is what charge controller size is needed for this setup? To manage these panels and batteries, the right controllers have to be used.

A 1000 watt solar array running on a 24V system needs a 60A charge controller. By dividing the solar power watts with the battery voltage and adding 25% for safety, you get the ideal charge controller size.

Calculate Charge Controller Size For 1000W Solar Array

In the preceding paragraph we just gave you the controller size needed for a 1000 watt solar array. But if you want to know how we arrived at this number, the math is really straightforward.

The formula is volts x amps = watts + 25%. So if a 1000 watt solar array is connected to a 24V battery, it looks like this:

1000 / 24 = 41.6

41.6 + 25% = 55.4

A 1000 watt solar system needs 55.4 amps. Rounded off to the nearest available charge controller size, that would be 60A.

Note that in the calculation, 1000 watts divided by 24 volts is 41.6 amps. Theoretically it is possible to run the array on a charge controller with 41.6 amps. But we do not advise this for safety reasons.

No system is perfect, and temperature, working conditions and other factors can affect a charge controller. You want the system to have some reserve power because solar power fluctuates throughout the day.

What solar voltage to use. The most commonly used solar power voltage systems are 12V, 24V and 48V.

  • Campers, vans, RVs and boats are designed for 12V systems, so use 12V solar panels and batteries there.
  • Most homes use 24V or 48V. The larger the array the higher the voltage should be. In the case of a 1000 watt system, 24V is ideal. For 3000 watts and higher, go with 48V.

What Type of Controller Should I Use?

A large solar system like 1000 watts will benefit more from an MPPT controller. A PWM controller is acceptable for small solar panels , but its deficiency becomes apparent with large arrays.

Suppose that the panels in the array is at 7.42 amps and the voltage is at 23.6. With a PWM controller the maximum output you get is 175.1 watts.

With an MPPT controller it can adjust the settings so the voltage reaches its maximum potential. In the case of 24V systems, that is 28.7.

7.42 x 28.7 = 206.2

This is a hypothetical scenario, and there are many factors that will affect the performance of a solar system. But the benefits of an MPPT controller is clear.

A PWM controller will only pull power just above the battery voltage. If you were using a 12V battery for instance, the limit would be 13V or 14.4V.

With an MPPT controller, the system will draw the maximum power the panel is capable of. So if you have an 18V solar array, the controller pulls 18 volts or close to it.

This applies to 24V systems as well. The bigger the system, the more you benefit from an MPPT. With 1000 watt solar arrays, it makes a huge difference in terms of performance.

Series vs. Parallel Solar Panel Connections

Another reason to choose an MPPT controller is it can work with different types of voltages With PWM they have to match.

If your solar array is connected in a series, it will increase the voltage. With a PWM controller, the battery and solar panel voltages have to be similar. So with a PWM controller, you are limited to a parallel connection where the amperage increases but the voltage does not.

With an MPPT charge controller you can wire the panels in a series. The controller will adjust the current to match the voltage for optimum results.

Suppose you have 5 x 200W 24V solar panels. If you connect these in a series the voltage will increase to 120 volts. A PWM controller cannot handle this, but a 48V MPPT charge controller can.

There are probably not a lot of instances where you need such high voltage. In some cases a parallel connection may be preferable. But this only goes to show the advantage of an MPPT.

Why a 1000W Solar System Needs a Charge Controller

Solar power is among the safest energy sources available, but it is not perfect. Solar arcing can occur, and without a charge controller you are putting the batteries at risk.

Auto Low Voltage Disconnect

As the name suggests, this safeguard automatically disconnects non essential loads from the system if the voltage drops below critical levels. This level is set in the charge controller and will vary per manufacturer.

If the voltage reaches this threshold, the safety trigger kicks in and automatically unloads. When the voltage is back at safe levels, the system starts charging again. This is an important feature that keeps the battery banks from overcharging.

Overload Protection

A charge controller works like a valve, regulating the current that flows into the battery. Without the controller the battery could become overloaded by the current coming in from the solar panels.

A 1000 watt solar array can overwhelm the battery circuit. This could cause malfunction or in a worst case scenario the battery might even explode.

With a charge controller this can be prevented. Adding extra protection like a circuit breaker to a solar system is recommended too.

Reverse Current Protection

Solar panel current flows in one direction. But in some cases the current may flow back. This is actually one possible reason why a charge controller seems to drain batteries. In fact this is likely to occur if there is no controller or it is damaged.

A reverse current protection is necessary to prevent this from happening. Without it, the battery will discharge continuously every night, leaving you in shock as to why the battery keeps losing power. This safeguard is especially important for large scale solar systems.

What Features Should I Look For?

The easiest way to go about this is to buy a solar pane kit. There are not a lot of 1000 watt solar kits available. However you can buy several smaller solar panels and ask the manufacturer for the ideal charge controller.

  • Type and size. Use the guidelines given here to decide what charge controller is suitable for your solar array. How you connect the solar panels is a factor too. If you have plans to upgrade in the future, take that into consideration as well.
  • Battery size and voltage. As explained earlier, an MPPT provides more options for solar panel and battery matching, but PWM controllers are more affordable. The type of controller must match the battery.
  • Temperature. Some charge controllers are designed to run under a specific temperature range. Operating beyond it might affect performance.

One question that often gets asked is “can you use more than one charge controller?” Yes, you can use more than one charge controller. In many instances, using multiple MPPT controllers is ideal, though it depends on how much solar you need.

Do make sure that you use only one type of charge controller, for example, two MPPTs. Keep in mind that all controllers have voltage limits that should not be exceeded. So if your solar array has more voltage than a single controller can handle, add another.

Tips and Warnings

  • Always follow the installation instructions.
  • AC loads should not be connected to a charge controller. Those are only for DC loads.
  • Place the controller as near the battery as possible. The closer it is to the battery, the more accurate the voltage measurement will be. This is crucial for optimizing performance.
  • Some appliances and devices have to bypass the controller and must be directly plugged into the battery. This is usually the case with low voltage devices. Check the appliance / device manual for information.
  • Some charge controllers are compatible with 12V and 24V systems, but others work with only one type. Double check before buying.

Conclusion

A lot of attention goes to the solar panels, batteries and inverters that charge controllers are sometimes taken for granted. That is a no no, especially with large solar arrays. With the right controller you are assured the system runs smoothly.