How many batteries can a 400-watt solar system charge?

A properly installed 400W solar panel system can fully charge 1 x 200Ah batteries, 2 x 100 Ah batteries or 4 x 50Ah batteries connected in parallel (about 200 Ah total) in about 4-6 hours each day.

The charging time of 4 – 6 hours of a 200Ah battery bank with a 400W solar panel system is based on:

  • the battery bank is discharged to only 50% of its capacity. If it is discharged more (bad for AGM batteries), they will take longer to fill
  • the solar panels are installed in a location that receives about 5 hours of sunshine.
    You will need more hours to charge the battery bank if it is installed in a location with fewer hours of sunshine.

The table below is an indicative guide of the number of batteries that you can connect to a 400W  system for a location with 4-6 hours of sunshine.

NoBattery capacity (Ah)No. of batteries
12001
21002
3504

Note: The table above assumes AGM, Flooded, or Gel type batteries that have a recommended depth of discharge of 50%.

A 400W solar panel system can fully charge 1 x 100Ah Lithium battery daily in a system.

Lithium batteries can be discharged up to 80% without damaging them.

Recommended battery bank size for a 400 watt solar system

To prevent the harvested energy from going to waste, the recommended battery bank size to use with a system this size should be 200Ah for AGM, Flooded of Gel type batteries.

If you are using lithium batteries, you can use 1 x 100Ah Lithium battery.

When you connect a larger battery bank larger than 200Ah, you run the risk of your solar panel system failing to fully charge it in a day which is bad for your battery bank in the long term.

Examples of appliances to connect to a 400W solar system

A 400W solar panel system can generate between 1,600-2,400 Wh of energy daily when installed in a location with 4-6 hours of sunshine.

Examples of appliances that a 400W solar system can run are:

  • laptop(s)
  • LED lights
  • desktop computer(s)
  • mini fridge
  • microwave (700-900W)
  • toaster (700-900W).

With larger appliances or if multiple appliances are connected, the battery run-time will reduce considerably.

Estimated run-times for appliances using a 400 watt | 200Ah solar system:

  • 40W Laptop, 28 hours
  • 70W TV, 14 hours
  • 130W fridge, 24hours assuming a 33% duty cycle

This assumes a system efficiency of 80% with a battery that has a depth of discharge of 50%.

To run AC appliances an inverter is required.

Inverter size to use with a 400 W solar system

A suitable inverter size to use with this system is the 1,500W or 2,000W inverter. In addition to the solar panels, batteries, and inverters, include fuse protection against overcurrent and short-circuit faults.

Protecting the 400 W system from faults: Fuse protection

Typical fuse sizes used to protect against short-circuit and overcurrent faults with this system size are as follows:

  • between panels and controller, 30A
  • between controller and battery, 30A
  • between inverter and battery, 150A

Related Questions

# 1. How long does it take a 400W solar panel system to fully charge a battery ?

A 400W solar system can fully charge a 200Ah battery in about 4-6 hours and a 100Ah battery in about 2-3 hours. If using a 50Ah battery (which will be a case of undersizing), the battery can be charged in about 1 hour.

Note: The above estimates assume a location that receives about 4-6 hours of sunshine and that the battery is only discharged to 50% of its capacity.

You can read this guide for more information on how long batteries take to charge with solar.

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