I'm testing my new solar generator setup, aiming to run my full-sized fridge and freezer solely on battery for at least 48 hours. To calculate the required battery capacity, I ran both appliances for 24 hours, which consumed a total of 3.18 kWh (2.06 kWh for the fridge and 1.12 kWh for the freezer). I've installed three 100Ah batteries in a 24V system, equating to 7.68 kWh, which should provide a comfortable margin for the 48-hour requirement. However, my initial testing shows only a bit over a day's worth of capacity remaining after starting the loads. Where did I go wrong?
3 Answers
It's also important to note that the estimated time on the inverter while both appliances are running might not accurately reflect real-world use. Traditionally, a fridge's compressor doesn't run constantly; it could only be active for about 1/3 of the time. So even if your inverter suggests 'one day', you could actually have longer runtime in practical situations.
One thing to consider is the type of batteries you're using. Lead-acid batteries typically only provide about 50% of their rated capacity, while lithium iron phosphate can offer around 80%. In your case, if you're using lithium batteries, you might be running close to the limits of capacity. Make sure to check how your batteries perform under load; undersizing could be the issue here.
Have you checked for battery imbalance? Sometimes one cell can be charged differently than the others, affecting overall performance. If you haven't, it could be worth looking into balancing the batteries. Also, estimated consumption based on running factors can vary significantly, especially with compressor-based appliances. Keep monitoring your usage and you might find clearer answers as you go along.