# Weird mobitronic Inverter problem ?



## nukeadmin (Oct 10, 2003)

I have a 600w sine wave mobitronic inverter fitted in my Euramobil, it was wired in by the company who fitted some other electrical gear, now it works fine when running up my dish, pc etc and screen, all relatively low ampeage equipment (Dish only draws .7amp during setup/alignment, and then <.3 during use, TV is LCD and low wattage and same for pc) now within 30 minutes of use, the inverter starts giving out its low battery alarm, and minutes later blows the 20 amp in line fuse between it and the +ve terminal on batteries. Now i have 2 X 105ah batteries, topped up by 2 X 75w solar panels, on a normal day i get around 2amps/hr charge incoming. The batteries themselves seem to lose charge quite quickly though i.e. fully charged (after being on hookup overnight) they read about 13.8v but after 30 mins on inverter using above configuration they are at 12.8v, does this sort of drain seem normal for that amount of kit hanging off my inverter ?

Secondly the acoustic alarm on the inverter is supposed to sound at 12.5 volts, but according to control panel the voltage it does sound at is 12.8v (I think this is because the cabling between the inverter and the batteries isnt really man enough (Thick) for the job at hand, and this would in turn produce the missing .3volt difference, that sound right ?

Finally any ideas as to why it blows the 20 Amp inline fuse ? It has an auto shutdown capacity on the inverter to protect discharging batteries totally but that isnt supposed to kick in until batteries are much lower charge ??


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## Anonymous (Nov 10, 2000)

Hi Dave

I have exactly the same unit and mine developed the same problem. I contacted the company and they sent a replacement under the warrenty. It was only a month old! 
My low batt. alarm was sounding continuously even with a fully charged battery reading 13.8 volts. The alarm should sound around 10.5 volts.
It looks like yours is draining the batteries too.. definately a faulty invertor. 
Mobitronic web site http://www.waeco.com/pages/home/index.htm

Jim


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## nukeadmin (Oct 10, 2003)

did yours blow fuses as well Scotjimland ?

mine is sounding at around 12.8v not as high as yours was ?

What about the state of my batteries, do those voltage drops seem ok ?


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## Maxonian (May 13, 2005)

There are several issues here, not least of which is why a 20A fuse is protecting a 600W inverter. 

At best, a 20A fuse will fail when the inverter is supplying 200W. You might easily exceed this with laptop, sat dish and TV. At 600W (and 90% efficiency) you need a 60A fuse, and wires capable of carrying the same. 

If fuse and inverter were fitted by the same company, I would question their ability to do this type of installation. 

This would be true irrespective of having a faulty inverter.

Some of these issues have been covered in a previous post.

Have you considered why 2 x 75W solar panels are only giving you a net 2A charge. I would have expected at least 4 or 5A. Is there a current drain in your MH which you are not aware of?


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## nukeadmin (Oct 10, 2003)

> Have you considered why 2 x 75W solar panels are only giving you a net 2A charge


Well we all know what pants weather we are having and i also have things like fridge, alarm system dragging current down slightly. On better days i have had as much as 4 amps being produced 

Scotjimland - Is your inverter fuse protected and if so by what rating ?


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## Anonymous (Nov 10, 2000)

Hi Dave

I installed myself and fitted a 50amp fuse. I also fitted an isolator rated at 100amps, I hate anything fitted that I can't disconnect if it develops a fault.


Jim


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## Anonymous (Nov 10, 2000)

Although I take the point about the 20a fuse being too small, the current has to increase as the voltage drops to maintain the same power - remember volts * amps = watts. 

The volts you quote seem _high_ if anything - a fully charged 12v battery left idle for a few hours will show about 12.65v. The only reason you're seeing more is becasue of the effect of the 'surface charge' which builds up when the battery is being charged.

A 20a load is quite a lot to sustain for hours even with a couple of 105 ah batteries - I wouldn't be surprised if you struggle to hold 12v after a couple of hours.


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## Anonymous (Nov 10, 2000)

Dave 

Are your solar panels connected when taking the voltage reading? If so you may be reading the solar panel voltages and not the battery, if not was the battery voltages taken whilst the inverter was under load or when the battery had been idle.

One other thing, similar thing happened to me last year, it was so obvious that I missed it, when putting the microwave in the cupboard I accidentally turned the charger off on the mains panel, took me ages to realise it.

Sounds as though two problems, Inverter + one other.

Ken


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## Anonymous (Nov 10, 2000)

With the previous posting in mind, this is what happened to me last year, as stated before, I accidental switch off the mains charger whilst at home, a few days later I was static for a few days on a none mains site and my batteries ran down my first warning was when the inverter alarm went off, I then decided to start the engine to charge them up but because the batteries were so low they drew more current than normal therefore blowing the 20amp charging fuse, on renewal the fuse blew again obviously, I ran a temporary feed from the vehicle battery to the leisure battery with a 40 amp fuse in line, all problems resolved on a temporary basis. I then realised about the mains charger and switched on. 

On returning home I beefed up the charging cable and fuse

Had I some solar panels in line when the batteries were low I believe they would have given minimal charge but would have shown a higher voltage (it would have to to enable it to charge) and could be misleading.

Ken


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## nukeadmin (Oct 10, 2003)

what type of fuses are u all using as my inverter is fitted with a standard automotive 20 amp fuses in a proper holder etc ?


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## Anonymous (Nov 10, 2000)

I’m using a 50 amp Maxi blade fuse in a terminal fuse holder on a 600w inverter 

Ken


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## 88724 (May 9, 2005)

*Aaaargh*

For 90+% of items a good modified sine wave invertor will power no problem.

Sine wave is very expensive, it also uses more quiescent current (ie the current drawn just to keep it "alive") for a Quasi sine its about .7 for a pure sine you are looking at 1.2 a (this is for good makes like Sterling)

The Invertor is faulty, 12.8 after half an hours use is OK, A fully charged Leisure battery will register 12.8 - 12.9 after 12hours rest (ie if it isnt used or charged) The 13.8 is the surface charge and soon dissapates its natural you have not lost any real power.

It as also been incorrectly installed it needs a bigger in line fuse, what size is not easy to gauge without knowing the specs of the invertor, because a 600 w invertor should have a peak power that it can maintian for a short while to start up things that have a power factor like motors etc so for peak it could run from 900 to 1200 w so a 75 to 100 amp fuse is called for.

BTW it is quite natural for it to blow a 20a fuse, dont forget even if the ampage didnt go up the invertor was warming up by then, the fan cutting in ?

George


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