Inverter Question - Leaving it Connected

[Darron]

I've just purchased my first inverter which I plan to use between the Disco4 and the caravan. It's the Kings 1500W Pure Sine Wave, which is probably much more than I'll ever need but seemed like good value for the money. The cables to connect it to the caravan/second battery are hard wired cables, however in the instructions it states 'when inverter is not in use, turn off and disconnect from battery'.

I wondered if anyone could help me understand what the definition of 'not in use' is (a day, a week, a month) and what would happen if I left it permanently connected? I've been searching Google for answers but not really found what I'm looking for.

Thanks, Darron

[p38arover]

I read not in use to mean when it is isn't being used to supply 240VAC, i.e., switched off.

Re disconnecting, I suppose it depends on what the switch in the inverter does. If it actually isolates the battery supply from the inverter electronics, you could leave it connected but off when not in use.

If you want to leave it connected, to be safe, it might be wise to wire in an external power switch.

Me? I'd hard wire it via another switch. Using clip leads would be inefficient and prone to misconnection. Using a cigarette lighter socket would be worse.

I suppose you could use an LV(32 volt) power socket and plug.

162109

162110

[Gav 110]

I would say if your not using it for a week or more
Maybe some 175amp Anderson plugs setup ready to swap between vehicles
Make sure you put cables in that will allow for volt drop at the highest current draw and fuses at the batteries
There are plenty of online volt drop calculators to help you
1500watts at 240 volts is more than 1500watts at 12 volts if you allow for loses
1500/12 = 125amps
Even if your not planning to use to full capacity I would allow for it
If you got it you will use it

[Homestar]

If you leave it on then it will continue to draw power from your battery. No load inverters can use a couple of amps sitting there doing nothing, the bigger it is, the higher no load current is drawn which is one of the benefits of not over speccing a unit by too much. Leaving it connected to the battery is generally fine though if switched off, although I run a battery isolator on mine anyway.

[p38arover]

Oops! I missed the 1500 watts - read 150 watts.
The plugs I mentioned would be a bit light duty for that!

Anderson plugs as suggested.

[trout1105]

I would simply put a heavy duty circuit breaker/reset switch between the battery/batteries and the inverter and leave it hooked up.
This way you can easily disconnect the power to the inverter when it is not in use [thumbsupbig]

[W&KO]

For the price of the Kings unit I’d buy two and permanently wire in....

If not than anderson plugs would be my next option.

I’m about to install my first inverter, I don’t believe there is a need to disconnect from battery, mine has a remote on/off switch that will be mounted next to where the outlet is.

[drivesafe]

Hi Darron, what are you planning on using that size inverter for?

When they are that large, they are not good for using for more than a few minutes when powered from anything but a large bank of lead acid batteries.

If you plan to run it for long periods of time, the total battery draw should not exceed 25% of the total battery capacity, and even this is a high constant current draw.

In your case, you would need at least 500Ah of battery capacity to meet a continuous high current draw.

Again, what is the intended use for that size inverter?

[p38arover]

Hi Darron, what are you planning on using that size inverter for?


Maybe to supply an initial peak load that would cause a smaller inverter (that's sufficient for the running load) to throw in the towel?

[Darron]

Hi Darron, what are you planning on using that size inverter for?

When they are that large, they are not good for using for more than a few minutes when powered from anything but a large bank of lead acid batteries.

If you plan to run it for long periods of time, the total battery draw should not exceed 25% of the total battery capacity, and even this is a high constant current draw.

In your case, you would need at least 500Ah of battery capacity to meet a continuous high current draw.

Again, what is the intended use for that size inverter?

Thanks to everyone for the replies and advice. Very helpful.

To be honest, it's not going to be used too much apart from charging laptops and the occasional device my wife packs which doesn't run on 12v (she's mentioned the Thermomix on a few occasions for strawberry daiquiris;). I completely agree that I may never need a 1500W inverter, and I made my buying decision pretty much on price alone as I couldn't justify spending anything more. The reviews also seemed really good which helped things.

Cheers, D.

[drivesafe]

Thanks to everyone for the replies and advice. Very helpful.

To be honest, it's not going to be used too much apart from charging laptops and the occasional device my wife packs which doesn't run on 12v (she's mentioned the Thermomix on a few occasions for strawberry daiquiris;). I completely agree that I may never need a 1500W inverter, and I made my buying decision pretty much on price alone as I couldn't justify spending anything more. The reviews also seemed really good which helped things.

Cheers, D.
Seriously, you would be far better off just telling your wife you can't power her Thermomix, and just buy a 300w inverter.

A 300w inverter will easily meet all the basic needs, like charging phone and camera batteries, charging an iPad or running a laptop.

You will not need anything special, other than ( recommendation ) using 50 amp Anderson plugs to connect the 300w inverter to what ever 12v power source you are going to use.

With something like a 1500w Inverter, you are going to need massive cabling, to connect between the power source and the inverter, particularly if you want to use it in any tow vehicle.

[Old Farang]

I wondered if anyone could help me understand what the definition of 'not in use' is (a day, a week, a month) and what would happen if I left it permanently connected? I've been searching Google for answers but not really found what I'm looking for.

Thanks, Darron
The answer is more semantics than anything else! As posted already, if it is not producing AC, then it is "not in use". But if it is drawing current when connected to a battery, then it is "switched on". The unit on-off switch SHOULD be double pole and disconnect the battery source when in the "off" position, but unless you have a circuit diagram and know how to read it, the only way to be sure is to measure the current of the input cable(s) in both positions.

ALL invertors will draw current when switched "on" regardless of any load, albeit most of them less than 1 amp or so. They are also most inefficient at low load conditions, which is why some of the answers here are asking what you are going to use it for? This can mean that the current draw from your battery if just using it to charge a phone, may be twice what is actually needed, ie; only 50% efficient. At their full rated load they may well be around 90% efficient.

Really, a 1,500 watt invertor should be used on 24 volts to be of more use and halve the input cable size.

Whatever it is, make sure to mount it in the coolest place that you have and that the cooling fans are not obstructed.

[DiscoMick]

Wouldn't recommend using an inverter for a Thermomix - we have several in our extended family and they draw a lot of power.