Inverters

[andrewa]

I have just got an inverter, great I think, can now run 240v kit but according to the installation guide cables should be routed no further than what is supplied about 2m my batteries are in the engine compartment at the back. What do I do to get around this mount the inverter in the engine bay and then run a lead from the plug socket into the cabin. Your advise would be appreciated.

Tks

 

[saturn]

i am fitting the same at the moment,my opinion is it is safer to extend the low voltage side cabling (12volt dc) and use the inverter ac side as supplied.
by the way, used to supply my laptop it pulled 3.2 amps from battery.

 

[seahorse]

Follow the manufacturer's advice & keep the 12v leads as short as possible in order to keep the voltage drop to a minimum otherwise the inverter will cut out earlier as the main battery voltage drops. My inverter 12v leads are about 600mm long. I fitted an earthed RCB & ran 240 to switched sockets.

 

[bedouin]

The trouble with inverters is that they draw 20 times the current from the 12v supply than they supply to the 240v. So to provide 1A current at 240V they are drawing 20A from the battery. Since current is the limiting factor with most cables it is clearly much easier to extend the 240v side than the 12v.

The reason the manufacturer recommends mounting it close to the batteries is to keep the cable run, and hence the voltage drop, to a minimum. It is possible to extend the 12V side, but it requires thick cables, and you would probably would need to replace the leads provided entirely.

 

[saturn]

how much voltage drop do you calc from 600mm of cable?.
i would not put an ac source anywhere near dc battery.

 

[pvb]

Depends...

To some degree, the answer depends on how powerful your inverter is. If it's a smallish unit, there's no reason why you shouldn't have longer DC cables, as long as they are adequately sized to keep the voltage drop to acceptable levels. If it's a very big unit, the size of the DC cables needed may persuade you to keep it closer to the batteries.

Another factor to bear in mind is the ambient temperature of the inverter. You'll find that many inverters don't like the heat in an engine compartment, and that higher efficiency can be achieved by mounting the inverter somewhere cooler.

 

[CraigBradley]

Re: Depends...

My little 80W inverter has a short cable with a cigarette light fitting - I have a socket in my main switch panel. Should I connect directly to a battery through a fuse? I've run an 8W fluorescent tube inspection lamp recently which began to melt. It was fine when plugged into the mains. Any advice?

 

[tr7v8]

Re: Depends...

It depends on what the socket and associated wiring are designed for.
An 80W inverter will be pulling circa 8Amps min. and long term that will overheat the cigarette lighter type socket and some of the others that are sold for auxilary usage.
Also if the cabling is a bit on the small side you'll find that once the voltage drops a little A. the regulation of the inverter will go to pot eg. not 230V AC and B. if it has auto shutdown on low volts thenit will shut down that much earlier.

Jim
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[pvb]

Cigarette lighter sockets...

...are generally good for 10-15 Amps, so your 80W inverter should be OK used in the socket. You should check that the supply to the socket is suitably fused, though.

No idea why a fluorescent should begin to melt.

 

[tr7v8]

Re: Cigarette lighter sockets...

Ummm, only the better quality ones can manage 10+Amps, despite their ratings, I've seen cheap ones melt at 5Amps especially used for any length of time.
As regards the Flourescent light I wonder if it had a poor connection inside and this has heated and melted.
Where was the burning, at the tube connections or internally?

Jim
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[bedouin]

Re: Depends...

Most cheap inverters produce a square wave - or perhaps a modified sine wave, rather than the pure sine wave from conventional mains.

This can be a problem for 'inductive' components such as transformers and chokes (and some motors) It is possibily this that is causing the tube to overheat.

The best solution in that particular case is to get an inspection tube that runs off 12V

 

[CraigBradley]

Re: Depends...

yea, the lighter socket does not look the highest quality and was indeed getting hot during the tube melt down - it was the black handle part that started melting in 2 places - suppose where in contact with internal metal. Good call, the 12v inspection light is now on the 'to get' list.

I'm guessing that a more permanent fused connection is probably safest at this stage.

thanks all

 

[andrewa]

Thanks for all the advise will see where best to site the inverter and then measure.

Andy

 

[lauradee]

mounty it close to the battery

and run the 240 volt cable to it
stu

 

[lauradee]

ps the higher the voltage

the less the amperage and the thinner the cable needed to carry the supply
#stu

 

[Robin2]

Re: Depends...

The overheating flourescent lamp may have been due to the quality of the ac power produced by the invertor. Only the expensive invertors provide a high quality sine wave like the mains AC power. The others produce some sort of cross between a triangle and square wave.

Flourescent lights are also difficult to work with, even with good quality power. In large installations (eg factories or offices) mains powered flourescent lighting can cause problems and electricity companies charge more on that account.

So you may have two difficult situations back-to-back.

You would probably be better to get a flouresent light that's designed to work directly off the 12v DC supply.

 

[saturn]

my last point,check your inverter has an earth stud on the case,check the output earth and nuetral are connected together and clamp both to anode.
also 16mm stranded cable will pass the max 800watt power at least 5 metres without problem.