G'day one and all! Hilly here from SA

[Hillysfolly]

That's simple and efficient. I'll have a go at doing something similar. I'll let you know how it goes. I'll grab relay next time I'm in city. I have most other bits on hand. What size inverter would you suggest for general camping use? And how accurate are manufacturers specs when they say 1500w peak3000w?

 

[Old.Tony]

The inverter's ratings are usually roughly close, I've not heard of too many complaints unlike what you hear about generators!

You have to choose something that will handle the peak load continuously without overheating. My fridge draws 380W on 240V so I'm using a 600W inverter. It happens that Aldi flog these inverters for about $59 and they're electrically isolated - so they're perfect. Powertech (Jaycar, Rays Outdoors, BCF) is also a good choice, the entire range is electrically isolated.

Be mindful of the amps that an inverter will draw. They're usually around 85-90% efficient and for a little 150W unit you'd just shrug and let it be. However, if you've got a 1500W/3000W inverter that's 85% efficient (and will supply 3000W peak) then its peak amperage drawn from the battery will be (3000/0.85)/12 = 294 amps. I recommend something a little better than leftover speaker wire for that!

 

[Hillysfolly]

So with all that, could I not have a couple of smaller (cheaper) inverter units matched more closely to the individual appliances they are to run? I actually have a couple of older (not sine wave) ones kicking around. I think they're 150w and a 300w??
A 300 watt jobby running a 200 watt light bulb would be more efficient than a 1500w unit running same load?

 

[Old.Tony]

Absolutely you can. There's nothing stopping you from doing that - the only thing you need to do at the end of the day is add up all the amps and make sure the cable is capable of handling that, and make sure the fuse matches too.

 

[Hillysfolly]

Yep reading you load and clear on cable size and fusing. Thanks for your input.

 

[Hillysfolly]

But how are you going to protect a circuit with your hypothetical 3000w load drawing 200+amps? Circuit breakers? Or a fusible link of some kind? Or a 'slow blow' fuse???
Haven't researched yet but those size fuses wouldn't be common would they?

 

[Hillysfolly]

Ok. Shoulda looked first. Answered my own question. 200a circuit breakers a dime a dozen on fleabay. Just never looked for em before.

 

[Old.Tony]

Always something to be found there. Found a 500A relay there the other day - perfect for putting in-line with your winch. It's better than the key-operated switch I'm using.