Inverter question

[noseoil]

I'm on hold on the build for a little while over the holidays, but still doing some planning & thinking. Wondering about a good inverter to use. I'm thinking 1,000 watts would be plenty for my needs (single group 27 deep cycle flooded battery). Wondering about different inverters out there. Most of the stuff will be running directly from 12 volts, but from time to time we may need a little 115v power & an inverter makes sense to have when necessary. Will have a generator as well, but a little bit of power is handy without dragging out the stinkpot & firing it up.

There are cheap inverters and very good ones in this power range, so is there a consensus about buying one which is durable, well made and affordable? I know you generally get what you pay for, but I've never used one & am starting from scratch on this stuff. Thanks, tim

[dales133]

I'd only go pure sine wave mate.
That way you can charge drill batteries and the like plus run anything at all as long as it's withing the wattage range of your inverter.
From the research I've done you want to aim for around double the wattage inverter or the max wattage of the apliance you want to run on it.
I plan on running a induction cook top that can run on different wattages but needs a minimum of 1000 watt inverter to run it at 500 watts so I'm looking at probably 3000 watts.
I'm no expert but I've looked around and in layman terms I think my explanation is pretty on the money.
There are some good inverters coming out of China on ebay and the inverter chargers will charge your battery when plugged into shore power

[MtnDon]

Choosing an inverter requires a couple of basic questions and answers, in order to make an intelligent selection.
1. What do you want to run off the inverter, and how long?
2. How much power can the battery or batteries safely deliver?

#1 may not be compatible with the amount of battery capacity available.

Re #1, The maximum watts that would be used at any one time will determine the max continuous output; that is easy enough to total up. However, the choice of power waveform must be made as well. Modified sine wave vs pure sine wave. Some devices like many chargers for tools and other small devices, electric motors, microwave ovens prefer pure sine wave and some will not operate on modified sine wave at all. Things that heat electrically like coffee pots are generally fine on modified sine wave. The more electronics there are in a device the more the reason for pure sine wave power; the life span of the electronics may be better. That's a broad statement, but in the off grid living world it has been found that modern appliances with electronic controls survive better on pure sine wave power. Sometimes you can't tell id the lifespan will be shortened on mod sine wave until the device fails. Regarding most devices with motors; motors run less efficiently on mod sine wave, they create more heat and heat is bad. Heat is also electricity being wasted. Power from batteries is precious and should not be wasted.

Re #2, A battery should never have more than half it's rated capacity used if long battery life is desired. Thats measured in amp-hours. A 100 amp-hour battery therefore should only be used to supply 50 amp-hours of power before recharging. 50 amp-hours at 12 volts = 600 watt-hours. An inverter will waste 10-15% of that as they are not 100% efficient. Take that into account.

Anyhow that a starting point.

[MtnDon]

So, yes that shows my bias towards pure sine wave. That said, I know there will be many folks who are using modified sine wave inverters and who are happy. That's fine. In some ways it's a little bit like choosing a battery. We should all know by now that marine/rv 12 volt batteries are not true deep cycle batteries like golf cart batteries are. But many of us get along okay with marine/rv batteries. Some of us, like myself, use two series connected golf cart batteries because we "must have" what is better. And in my case it must be said that I need the capacity to cover using the inverter to power an electric kettle, a coffee maker and a HD blender without always needing to run the generator.

[noseoil]

Don, thanks for the answer to my question. Since I'll be using some electronics from time to time, it sounds like a pure sine wave inverter is the way to go from the start. No need wasting energy & making heat. I figure the most I will need will be 500 watts, so 1,000 should be enough.