Power Inverters | Meet the Trudgians

Power Inverters

Posted by on Dec 9, 2016 in Featured, Technical | 5 comments

Power Inverters

Power inverters can solve an important issue when off-grid in a caravan or motorhome. It’s a way of generating mains power from your battery for a moderately short term period of time.

We have created a video that discusses power inverters. From how they work, why you might need one to some things to look out for when purchasing an inverter.

In the video, I reference this blog post and descriptions of some real world examples. So, watch the video then carry on to the bottom of this page for 2 examples of real world applications.

 

Before we start we need to set the scene. Let’s assume that in our caravan the leisure battery is rated at 100Ah. This means it can deliver 1 Amp of current for 100 hours. Or it can deliver 100Amps for 1 hour. Finally, Our chosen inverter is 80% efficient.

Example No. 1
A Laptop.

We will assume you want to run a laptop and its associated charger. For our example, we will assume it consumes 100watt of Power. The inverter will require power on top of this 100w, so we need to add at least 20%. Our total power drain will be about 120w to charge and run the laptop. Time for some maths :

1. Lets calculate the current drain, using the formula Current = Power / Voltage :
120w / 12v = 10Amps.

2. Now we know how much current we are taking from the leisure battery lets see roughly how long it will last. We can do this by dividing our Battery Ah by the current drain, so
100Ah / 10A = 10 Hours (ish)
I have said that the time will be 10 hours, this is really a ballpark figure. It doesn’t take into consideration the actual Inverter efficiency, the state of the battery or other environmental variations.

Example No.2
A Tappenaki Grill.

Many of these electric grills can consume 2,000w. add our 20% and we will need an Inverter that can deliver 2.4kW. Wow. So, again let us calculate the current drain :
2,400w / 12v = 200Amps

Not only with the cabling need to be ridiculously huge to handle such a hefty draw but again if we divide the Battery Ah the battery will last abut 30mins before completely dead.

 

So, I hope these examples are of some help. just remember that if you are out in the wilds and you need to use an inverter, be smart with it. Make sure that you have a way of recharging your battery and that you don’t over run an inverter unnecessarily.

5 Comments

  1. Thanks for another essential posting. Where else could everyone get that kind of information in their normal complete way of crafting? I have a demonstration incoming week, and I am searching for such information.
    Stuart Weitzman online https://stuartweitzman.artienatasha.com

  2. Hi, What inverter would be needed to run a 800 w microwave in my motorhome .Many thanks Dave.

    • Hi Dave, the short answer would be a 1600w Pure Sine wave inverter. But, consider hw long the battery would last with a 800w device running. That would be drain of around 66Amps, and would flatten a 12Ah Leisure battery in under 1 hour, and with that amount of fast drain, would quite possibly destroy or limit the life of the battery. Another thing to question, would be how quickly you could recharge the battery after that amount of draw.

      So, I hope that answers which inverter you should go for, but also points out some issues with running a high power device.

      Take care.

      • Thanks Dan , sorry but I have two 120 ah batteries linked together , and a 120 solar panel does this help my cause , for running a 2000 inverter Dave

  3. Hi, I have been watching your video’s and have a basic question. We have several small TV’s at home, all 240v. We have a boat which has a 120ah leisure battery and we also have a 150w inverter available. Would it make sense to run a 240v TV through the inverter or would we be better off just buying a 12v TV. The spare TV’s a burning around 40~50w. We only watch TV for a couple of hours at a time and when in a marina we can hook up to mains power. That said we sometimes go ‘off grid’ but we are worried about power consumption. Thanks Rich

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