Solar Power Guide
So you've decided on a portable camping fridge for your next adventure, and now you need to figure out how to power your gear. Researching this topic can often feel overwhelming with the wealth of information out there.
Firstly, you need to calculate how much power your gear is going to be using. If all you're running is a fridge then that's easy. Waeco have already tested all their fridges, and have given 24 hour cycle averages for each fridge. Keep in mind however that there are many variables at play when it comes to refrigeration, so it is always better to overestimate your power consumption.
If you are running other gear (for example lights), you will need to add this to your power consumption totals.
The two main conversion formulae are as follows:
Watts = Ah/h x Voltage
Ah/h = Watts / Voltage
If the power rating for a device is given in terms of watts, you can use these formulae to convert to 12V Ah/h. Then simply multiply this by the number of hours you intend to run the device for to give you the total Amps per day for that device.
Generally, you should have a battery bank that can power your gear for at least 24 hours. So if you are averaging 2 Ah/h, you'll want a battery bank of at least ~60 Ah (most AGM deep cycle batteries recommend against discharging the battery below 20% to avoid damaging the battery). The larger your battery bank, the less prone you are to bad weather.
Solar panels are a great way to power your campsite power needs. Not only are they far cheaper than a generator, but they don't make any noise and are far more portable! As a general rule of thumb, you should work with 5 hours of direct sunlight per day. To figure out how many amps your solar panel is going to be recharging per day, simply use the formula above.
For a 120W panel, it will charge at a maximum rate of 120/12 AH/h (10 Ah/h). Realistically you will not maintain a constant efficiency of 100%, so it is good practice to multiply this number by 0.75 to allow for unforeseen variables. Therefore, we can expect a 120W solar panel to charge at a rate of 120*0.75/12 = 7.5Ah/h. So 5 hours of direct sunlight will charge ~37.5Ah back into the battery.
If we are averaging 2 Ah/h (or 48Ah per day), our battery is going to slowly drain as we are using more power than we are charging back in! If we do the same calculation for a 160W panel (which can be achieved using two Waeco 80 Watt panels) our system will charge 50 Ah in 5 hours, giving us an energy surplus.
While it is important to have a battery bank that lasts at least 1 full day (to be safe really you should have a battery bank that lasts for 1.5 to 2 days), the amount of solar panels you need depends on how long you plan to camp for. For instance, if you plan on camping for 5-7 days, you do not need a solar system to keep you running indefinitely.
For example, let's say you have a 120Ah AGM battery with an 80W solar panel. At an average power draw of 2 Ah/h, you would be using 48 Ah per day, while an 80W panel will charge ~25Ah per day (with 5 hours of direct sunlight). I will use a table and graph to illustrate how long this system will be capable of running (assuming the panel is running at 75% efficiency with 5 hours of direct sunlight each day).
|Remaining Capacity (Ah)||80W Panel||120W Panel|
As you can see, even a small 80W panel will get you through a long weekend camping trip, while a 120W will give you a solid week away. For this scenario, a 160W panel setup would keep you running indefinitely (unless you get a string of bad weather, in which case a larger battery bank would be useful). If you want your system to run indefinitely (let's say you're going away for a month) then having a couple days of reserve battery power can be very useful, as the chance of having some bad weather increases over time.