Inverter appliances vs 12V
Complaints about poorly performing refrigerators ranks up there with battery performance as one of the most frequently-mentioned issues bothering an RV owner. The drain on battery power coupled with poor performance of many RV fridges means you really don’t get much bang for the crazy amount of bucks that an RV fridge costs to both purchase and repair.
Whilst some travellers are happy to jump from caravan park to caravan park and run their fridge from gas while they travel, there are a growing number who want to free camp away from the crowds and are alarmed at how much these gas guzzlers can take to run.
Now I’ll admit we don’t hear many complaints about air conditioners, because frankly, the possibility of running an air conditioner from a battery hadn’t even been contemplated until lithium batteries came along.
On this page we want to put forward the case for considering a 240V domestic inverter fridge or an inverter microwave in your RV.
Not that type of inverter
The inverter in a fridge or air conditioner has nothing to do with the other inverter that changes battery voltage to 240 volts. This type of inverter in a fridge is known as a variable-frequency drive (VFD). This is a fairly complex subject, so best to Google it if you want to know more.
The pros of a modern inverter fridge
- A domestic fridge is significantly cheaper to buy than an RV fridge.
- It will do a better job of keeping your food cold, especially when the ambient temperature is high.
- A modern inverter fridge will use less power, but more importantly, a lot less power to start up.
- It's easier to find a repairer for a 240V domestic fridge than an RV fridge.
- If the thing packs up and dies, you're replacing roughly $500 worth of appliance instead of about $2,000 worth.
- You get a lot more actual internal fridge space from an inverter fridge of equal outer dimensions.
The cons of a modern fridge
- You need a Pure Sine Wave inverter (on the flip side, you can use that inverter to power other things as well as your fridge).
Inverter microwaves
Did you know that when you use your microwave at 50% power, the microwave is actually running at 100% power for 50% of the time. You can actually hear the microwave turning on an off as your food goes round and round.An inverter microwave, on the other hand, when running at 50% power, will actually run at 50% power for 100% of the time. Because of this, you can run an inverter microwave on a smaller inverter
How an inverter motor works
A low-voltage, or DC motor is a single-phase motor. A modern 240V inverter motor is a three-phase motor. This three-phase motor is actually changing the voltage and the pulse length of the wave coming from your power supply to each phase of the three-phase motor. This is called a VFD, or Variable Frequency Drive and it controls the speed of the motor.
The advantage of an inverter motor is that it can start up slowly - it doesn't have to start at full speed. Three-phase motors take one third of the amount of effort per phase than a single phase. It's basically spreading the load across three separate parts of the motor, each part being a much smaller load than the one big load for a single phase motor where the whole high-current draw involves first getting that motor to start turning. Once it's turning, the current required to keep the motor turning gradually drops.
The point of this is that the single-phase motor requires enough power to start, even though it doesn’t require as much to continue running. So the this affects the size of the inverter you need to provide the 240V power.
An example
A 250 litre fridge that doesn't have an inverter motor requires approximately 1000 watts to kick its motor over to get started and requires power from an inverter of at least 1000W. The same size fridge with a 3-phase motor requires a third of that power to get started and could be powered by a 350W inverter.
An inverter converts low-voltage DC power to 240V AC power so that you can run 240V appliances. Not everyone wants or needs an inverter, so we look at why you might want one, how to choose a size, the importance of standby current, and the difference between pure sine wave and modified sine wave.
The lure of air conditioning whilst free camping is often what brings customers to us for a lithium battery install. But you also need to think about how much solar you’ll need to replace the power you use.