A 12V/400Ah battery bank may be just what you need to backup power in your home, boat, or RV. The cost of one is not trivial.
A LiFeP04 battery bank may cost as much as US 1,600 at current market prices and so keeping your solar battery bank topped up cannot be emphasized if you want your batteries to last.
With that said, how many watts of solar should you use to charge a 12V/400Ah LiFEP04 or AGM battery bank? What size of inverter (watts) do you need?
Read on to find out this, and more
Note: The information provided assumes that the battery bank is discharged to the maximum recommended levels of 50% AGM and 80% for LiFeP04 batteries.
If the power consumption of the connected appliances is much lower, you can get by with fewer watts of solar.
How Much Solar to Fully Charge 400Ah Battery?
Well, how much solar you need mainly depends on:
how many hours of sunshine your location received,
how much energy your appliances will be drawing from the bank on a regular basis, and
also the voltage of the battery bank (12V, 24V, or other)
Charging a 12V, 400Ah AGM Battery bank with Solar
You’ll need about 2kW of solar to keep a 12V, 400Ah AGM Battery bank (4,800Wh) charged regularly.
Note: This assumes your location receives at least 4 hours of sunshine and that the batteries are discharged only to 50% of their capacity!
24V, 400Ah AGM Battery bank?
This bank has double the capacity (9,600 Wh, from 24V x 400Ah) and will require about 4kW of solar.
12V, 400Ah LiFeP04 Battery bank
You’ll need about 2kW of solar to keep a 12V, 400Ah AGM Battery bank (5,120Wh from an effective voltage of 12.8V x 400Ah) charged regularly.
Note: This assumes your location receives at least 4 hours of sunshine and that the batteries are discharged only to 50% of their capacity!
24V, 400Ah LiFeP04 Battery bank?
This bank has double the capacity (9,600 Wh, from 24V x 400Ah) and will require about 4kW of solar.
How many solar panels?
This depends on the capacity of watts used in building the solar array.
You can for instance attain 2kW of solar using 10 pcs of 200-watt solar panels, 20 pcs of 100-watt solar panels, or 5 pcs of 400-watt solar panels.
Note. This list of possible solar panel connections is not exhaustive.
How to Connect the Solar Panels
Take note of the maximum input voltage of the hybrid inverter or charge controller.
Connect the solar panels in series such that the effective voltage does not exceed the maximum input voltage of the hybrid inverter or charge controller.
For example, if you are using a 200-watt (24V, 8.3 amp) solar panel as a building block for the solar array then connecting the 10 x 200w solar panels in series results in an effective voltage of 240V.
If the charge controller or hybrid inverter can handle a maximum voltage of 450V, then you can go ahead and connect the string of series panels to the charge controller or hybrid inverter without damaging it from an overvoltage!
How Much Space (sq. ft) for the Solar panels?
Assuming each 200-watt panel takes up about 12-14 sq. ft, for 10 solar panels, you’ll need at least 140 sq. ft of available space to mount them.
How Long to Charge the Battery Bank?
While charging time varies depending on the extent to which the batteries are discharged and how much solar is available, the battery bank should be able to fully charge in about 6-8 hours provided it is not discharged beyond the recommended levels (50% for AGM and 80% for LiFeP04 batteries).
Related Topics
1. What Size of Charge Controller?
This really depends on whether you plan to connect the solar panels in parallel or in series.
Make sure the voltage of the solar array does not exceed the maximum solar panel voltage that the charge controller can handle!
Therefore wire the solar panels – series, parallel, or both to remain within the limits of your charge controller.
Not sure what to do?
Then this calculator that works out the maximum number of solar panels to connect in series or parallel depending on the power output of solar panels and the charge controller specifications may be of help.
2. What Size Inverter for 400Ah Battery?
The inverter size depends on the combined power consumption of the connected appliances (watts) and the battery bank voltage.
Consider a 3,000 – 5,000 watt inverter for use with the battery.
Of course, you could use a smaller capacity inverter too. Make sure that the voltage of the inverter used matches that of the battery bank.
For example, use a 12V inverter model in the case of a 12V battery bank and a 24V model for a 24V battery bank.
3. What Size of Charger for the Battery?
Consider a good quality 60-80 amp rated charger for your 400Ah battery. Make sure to consult the technical specifications section for your battery for the manufacturer’s recommendation.
Closing Thoughts
You’ll need about 2kW of solar to keep a 12V, 400Ah AGM or LiFeP04 Battery bank charged regularly.
Note: This assumes your location receives at least 4 hours of sunshine and that the batteries are discharged only to 50% of their capacity!
Recommended Posts
