A deep freeze is an important appliance in any home for preserving food for long periods of time. If you don’t have access to grid electricity, you might be asking how many solar panels are needed to power a deep freeze?
Three 100-watt solar panels will be enough to supply 108 amp/hours of electricity each day, which will be enough to charge a battery bank capable of running a deep freeze for four days without the sun.
How much power does a deep freeze need?
A deep freeze will essentially be powered by batteries, which solar panels will charge. Batteries will provide the constant power supply needed by the deep freeze to be able to run effectively.
The first step is to calculate the amount of electricity needed by the deep freeze in amp/hours per day.
Most compact fridges/freezer’s power ratings are in the range of 70 watts, with more expensive freezers can be as low as 40 watts.
The power used by the deep freeze:
If we use 70 watts then: 70watts/12 volts = 5.8 amp/hours.
The next thing to remember is that a deep freeze will consume more energy in the summer than in the winter due to greater temperatures and the compressor being on for longer periods of time.
Daily power usage of deep freezer
| Summer | 75 amp/hours |
| Winter | 58 amp/hours |
Our deep freeze will thus need 75 amp/hours per day in summer and 58 amp/hours per day in winter to run.
You will use this figure to calculate the battery capacity that you will need to run the deep freeze.
What battery capacity are needed for the deep freeze?
Assume that we have a few wet or gloomy days where our solar panels receive minimal sunshine. Let’s choose a battery with adequate capacity to keep the freezer running for four cloudy days.
75 amp/hours x 4 days = 300 amp/hours
Unfortunately, if a deep cycle lead-acid battery is discharged over 50%, it will be damaged. So we’ll need 600 amp-hours (or more) of battery capacity to store 300 amp-hours of electricity.
You must select batteries that can withstand repeated deep discharges. If car batteries are utilized in this manner, they will fail after only a few months.
6 x 110 AH deep-cycle batteries like the Renogy deep cycle AGM battery or Mighty Max options will work well.
Another option is to use golf cart batteries like the 6 V Trojan T 105. Each of these 6 Volt batteries has a storage capacity of 225 amp-hours. Two of them connected in series will provide the required 12 Volts DC, but only 225 amp-hours—insufficient to power our freezer for four cloudy days. We’ll need six batteries to get 600 amp-hours of capacity.
How many solar panels are needed to charge the batteries?
How much current is generated by a 100 Watt solar panel? The peak power output of solar panels is advertised in perfect conditions. Because solar panels produce electrons at around 16 Volts of pressure, the current produced by one 100 Watt panel during one hour of full sunlight is:
100 W / 16 v = 6 amps
In the summer, a single 100 Watt panel produces 6 amps per hour x 6 hours of sunlight per day for a total of 36 amps of current per day.
Keep in mind that our freezer requires 75 amp-hours every day. As a result, one 100 Watt panel is insufficient. We’ll need three panels for a total of 300 watts. Three 100 Watt panels will give you 108 AH per day, which is more than needed, but you can always use the extra capacity to power other appliances.
Another option is 2 x 120 Watt panels will give you 90 AH hours, which will also be sufficient.
How to prolong battery life
- Use a charge controller. – Batteries are damaged when they are overcharged. Using a charge controller will shut down the current from the solar panels when the batteries are full, preventing them from being overcharged.
- Use a depth of discharge (DoD) of 50%. – Lead acid batteries are damaged when discharged any further than 50%
- Consider adding extra batteries. – Adding extra batteries to add more storage capacity will result in the batteries being discharged less, resulting in a longer life.
- Use grid power when available to run freezer– Using the grid power to run the freezer will also prolong the battery life.
Key Takeaways
- a Deep freezer will use 50 – 70 AH per day, depending on the season
- Calculate the battery capacity needed based amount of days storage needed to run the freezer
- Try to prolong battery life by not exceeding a DoD of 50%, using a charge controller and adding extra battery capacity if possible.
