# Beep from inverter



## chrisndeb (Feb 7, 2007)

Hi All

Im not to good with inverters so hes my question (it may seem daft to all of you)

We have a 300w which runs from our 110amp Battery, we run a small flat screen lcd tv and a normal 240v sky box, we use a double plug in the inverter to allow the 2 plugs to plug in.

I have run a 2 core cable (a long cig lighter extension lead) from the cab where the battery is to the wardrobe mid van with a female cig lighter which i connect the inverter into using the male cig lighter connecter it came with. 

All works fine for a few hours, the battery meter shows still loads of power but the inverter starts to beep?

I have a 600w inverter which clips to the battery with leads like jump leads (big) if I run a 240v extension lead from the inverter in the cab to the tv & sky box would this work, more to the point will it be ok? 

Thanks

Chris


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## DiscoDave (Aug 25, 2008)

The buzzer is indicating low voltage. Most likely below 10.5v into the inverter. Voltage drops in relation the current draw, size and length of the cable used.

as a simplififed example if the volt drop is 2 volts and is effective on the 12v side of the invertor that is a 16% drop.

if you swap invertors anduse a 230v extension lead the 2 volt volt drop applies to the 230v side of an invertor and is only 0.9% of the total and so has no effect on the appliances used.

hope this goes some way to explaining it for you.


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## chrisndeb (Feb 7, 2007)

Thanks DicoDave

Would it work the same if I put the 300w inverter on a short lead by the battery and used a 240v extension lead? as the smaller inverter is silent?

Thanks

Chris


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## DiscoDave (Aug 25, 2008)

certainly would do yes.


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## HarleyBiker (Apr 16, 2009)

Hi chrisndeb,

I think your problem is that the 12v cable feeding the inverter is too light (thin) causing voltage drop. I will be ok when the batteries are in titp top condition but as they discharge slightly, the loss will be too great.

If you replace this with a thicker cable it should present a cure.

The problem is that whilst a 300 load will draw only 1.2 amp (approx) whilst plugged into the mains, when used through an inverter it will draw approximately 25 amps, far too much for your cigarette lighter extension lead.

I hope this helps.

John.


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## Touchwood_RV (May 1, 2005)

Hi chrisndeb,

All of the above are technically correct what you are missing is, if you really want the inverter nearer the 240V appliances then you need to calculate the cable size, the following are examples, I have made a couple of assumptions:
1 – this is for a permanent installation
2 - cable run will NOT be run in constricted places (i.e. within insulation, or through bedding lockers that are then stuffed with bedding/sleeping bags etc)
3 – if the cable is routed outside, clipped to the chassis, it is enclosed in quality conduit to prevent damage

At 300 watt for a 1 meter run you need a cable with something around 2.5mm cross section per leg
At 600 watt for a 1 meter run you need a cable with something around 6mm cross section per leg

At 300 watt for a 3 meter run you need a cable with something around 10mm cross section per leg
At 600 watt for a 3 meter run you need a cable with something around 16mm cross section per leg

The above are sample calculations and not to be taken as givens, as the actual final size will depend on conductor type, copper or aluminium, and the type of cable insulation which needs to be correct for the installation area/materials within in which it is run for permanent installations. 

All the above will provide a reasonable/acceptable voltage drop but will result in the provision of large unsightly cables being run.

Personally I would consider the location of the inverter in respect to the power source and then run a good quality 2.5mm 3 core flexible cable permanently installed from the inverter socket outlet to a new twin socket adjacent to the TV and Sky box into which you plug these when on inverter and back into the original sockets when on mains/generator.

In respect of the inverter location you need to consider heat dissipation of the inverter, securely mounted and not allowed to mix with the battery gases for safety reasons.

Or something in between for temporary use installation, correct cable size kept short from battery to inverter then an extension lead to the appliances - just a possible accident risk of tripping on cables etc… Actually exactly what you suggest in your last paragraph – please consider where the inverter will live temporally – heat, wet, mixing with the battery gasses.

I hope this helps you appreciate the issue you have and that there are solutions to it – no need to give up, a good sparks in your area or at your dealer will be able to do the math/design etc for you…


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## chrisndeb (Feb 7, 2007)

Thanks for all your help.

I will move the inverter to under drivers seat and replace the cable with thicker 3 core.

Thanks

Chris


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