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Solar OFF Grid power

Solar OFF Grid power comes in rescue where the energy demand in remote locations. In the remote locations where there is no access to local run utility power supply."" />

Solar OFF Grid power comes in rescue where the energy demand in remote locations. In the remote locations where there is no access to local run utility power supply.

Solar OFF grid power backup is the best suit to meet the energy demand. it is a very similar to the “Hybrid Solar” power except the fact that one will not have access to the rely controller which prioritizes the source of power.

Here the single source of power to charge the batteries are only from Sun light. This reduces a component addition to the circuit which is the rely controller.

Solar OFF Grid power


 Solar OFF grid power setup
A typical solar off grid power setup

It is important to make necessary calculations for the circuit. 

The batteries are the power source stores the solar power in them during the day and discharges the power on demand.

The Solar OFF grid power setup gets bulky depending on the

  • Number of hours power is required (additional batteries have to be included),
  • Number of hour sun light is available
  • Number of solar panels required to pump the power to these batteries
  • The appliances peak load requirement.

DC has high current value hence the solar off grid power system design must consider in withstanding this current which is vital to charge the batteries.

The following information shall help to evaluate the setup and components required.

RULE-1 -- Inverter capacity

In the Solar OFF grid power setup the Inverter capacity decides the ability to handle the AC load,

The rule is simple, if the load is less than 800 watts/hour a 12V DC run system would suffice the need.

In order to understand the capacity figure out the wattage of appliances that would run on a concurrent power usage.


Appliance1 (TV) = 30 W

Appliance2 (5 Lights of 10W) = 5x10 W = 50 W

Appliance3 (Laptop) = 60 W

Applaince4 (3 fan of 40 W) = 3x40 = 120 W

Total power usage = sum of all appliance power consumption

= 30 W + 50 W + 60 W +120 W

= 260 watts

The major drawback in the 12V DC system is its ability to handle the power demand is limitedas additional inclusion of batteries in parallel will increase the DC current.

However for simpler load and longer hour power supply in lesser wattage this still can be used.

It must be noted for higher the watt hour (Power) consumption a higher inverter capacity should be used usually a 24V inverter setup, this would take care of higher loads

The ability to supply power in hour duration would be limited depending on the usage. A 1600VA inverter would fit the purpose. Interested to pickup inverter of choice - Follow the link.

RULE-2 -- Energy utilization per day in watt hour

In the Solar OFF grid power setup the different appliances are used for different purpose at different intervals of the day. The peak daily power consumption is calculated with their hours of operation and thus nailing down the watt hour per day requirement.



Peak power consumption in (watt)

Number of hour of operation (hour)

Total Power consumption by device (watt hour)





5 lights of 10 W




Laptop of 60 W




3 Fan of 40 W




Total power use per day =


For optimal system design its practice to design 50% more to capacity

= 1560 + 50% (1560)

= 2340


RULE-3 -- Number of days the power can be drawn from battery

A perfect Solar OFF grid power setup the design must consider the fact that no two days are similar in obtaining the sun light, the seasons vary locally due to earth’s atmospheric behavior etc.

Hence it is vital to design the solar back up system to hold the backup charge in battery for minimum of 2 days to 5 days. In other words based on the watt hour requirement per day, the battery capacity should have 2 to 5 times ability to store and supply power for optimal uninterrupted operations.

In practice the number of batteries those require to be included in the system would increase.

RULE-4 -- Calculating battery power storage capacity

The initial steps in Solar OFF grid power provided information to understand the minimum power required. Now this power requires to be stored in the battery, the minimum power that should be available form a battery at any given point of time in accordance to the number of days we require power from battery without recharging them.

In our above example 2340 watt hour per day is the minimum required power that will be consumed.

Now number of days we expect the batteries to discharge this power without recharging = 3 days (let’s assume)

Hence we need 2340 watt hour x 3 days = 7020 wh

It should be noted batteries should never be drained or discharge power less than 50% of their rated capacity, this will decrease the life of the battery and the charge holding capability. Thus (7020 wh x (1/50%) = 14040 wh ) should be the minimum power that should be readily available from the battery to discharge.

Power = Voltage (x) Current

To calculate the battery capacity (Ampere Hour or AH). Inverter system can be of 12V/24V/48V depending on application use. In this case we assume 48V. Hence

Current = Power / Voltage = 14040 / 48 = 292.5 AH approximately 300 AH battery is required.  Interested to pickup battery of choice - Follow the link.



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