Inverters

[Jim Beck]

I want to buy an inverter for my H33. A West Marine technical article recommends that, in deciding on an inverter, the maximum wattage should be such that the amp hours of your batteries are at least 20% of that amount. The amp hours of my two-battery bank is 200, which would suggest an 1000 watt inverter. My question is would a larger inverter (say, 1800 watts) really create a problem as long as used carefully? Seems like the extra capacity would be useful for short term, higher wattage uses, such as brief use of microwave, while some other lower wattage appliance was in use..

Thanks for any insight.

 

[Stu Jackson]

Jim, your larger approach is correct. What WM is indirectly advising is to have a large enough battery bank to support your USE of whatever inverter you buy. If you buy an inverter that is too small for your intended appliances, it'll be no good for your, right?

What you need to do is an energy budget for your USE of the inverter and the loads you plan to use with the inverter, and compare that to your house bank. The result will essentially tell you how long you can use your appliances.

It's like the variables of time, speed and distance.

 

[Benny17441]

Your thinking is correct and Stu's suggestion about conducting an energy budget is right on the money. You have to consider your appliances, anything with an electric motor like a small refrigerator or a power tool will be rated for a running load but may require a surge of up to 3 to 5 times that power to get that motor started. The other side of the coin is that an inverter is most efficient when its output is closely matched to the load. In my estimation practicality trumps efficiency but you would not want an inverter so large that it would normally be underutilized most of the time. I think an inverter in the range of 1500 to 1800 Watts would be very adequate for a weekender or coastal cruiser boat with a modest size battery bank when used prudently.

 

[FourPoints]

While I'm not running a microwave, I do run power tools from time to time. I installed the Xantrex prosine 600 and haven't came across anything I needed to run that I couldn't run with it.

Make an honest assessment of what you are going to use the inverter for, size it appropriate, and make sure your batteries can handle the load you want to use it for.

Then you need to consider your charging system and ensure it can really really recharge the batteries in a timely manner, but that is a whole other topic.