Running fridge on invertor.

[chippieshaun]

Hello all
Well , i finally got my fridge working again today which now brings me to the thing i have been pondering for a while.
The fridge is not very good on 12v and i read something a while back about ditching the 12v side and just using an invertor to power the fridge via the 240v side , when on the move.
The supply to the invertor would be from the vehicle battery , via the existing fridge relay. So i would just take the existing feed to the 12v element of the fridge and wire into an invertor........and so plug the 240v plug(from the fridge) into the invertor and hey presto!!
It make sense , right? It means that , when driving, the fridge is running much more efficiently and is thermostatically controlled.
Or am i missing something really obvious?!!
And if it is such a great idea (i'm thinking it is at the moment!) then why have i never heard it being discussed on here??
Has anyone done this or got any thoughts??
If it is all good then what power invertor would i need to get? Am guessing it wouldnt be anything too mad........300w??

Look forward to hearing a few responses
Cheers
Shaun

[AngeloEvs]

It was discussed and, whilst opinions varied, this is becoming a popular modificatiom. You simply plug the 13A plug from your fridge into the invertor, use a domestic extension lead if necessary.. As long as your invertor is capable of supplying a minimum 150W so that it has a bit of 'headroom' you should be OK. Nothing special required from the invertor as it is only powering a resistive load. You will draw slightly higher current from the battery but the power transfer to the 240V element should be better, and like you say will have the advantage of the thermostat. Leads from Battery to invertor should be short as possible. Set the thermostat for a mid setting to start with. However, if the fridge is 'knacked' you will still have warm beer irrespective of which element is powering it.

[Mocki]

great idea, BUT this means you will have to keep unplugging the fridge everytime you stop where there is a hook up, and plugging it into the mains feed....

invertors are really hungry on the 12v,(And not to be trusted unattended) and lets be honest here, unless your 12v element is FuBaR you are not gaining anything really..... thermostat controlled only means it switches in and out at set temp, not that the invertor switches on and off,so no better for the charging sys, worse infact! imo

[AngeloEvs]

Just read your post again and you mention using the existing 12V element wire for the invertor. You shouldn't do that as the wire is the cause of the problem with the 12V operation. Usually because the run from the battery is quite long and power losses occur in the cable. You will still have the same problem if you use this wire for the invertor. The Invertor MUST be placed as close to the battery as possible for it to run efficiently. On 240V operation the current is less than 0.5A so use a domestic mains extension lead and connect the fridge into that. You didn't say whether the fridge performed better on 240V operation compared to 12V and it might be worth doing a comparison. The alternative to using an invertor is to upgrade the 12V feed to a much heavier grade of cable thereby reducing the power loss if the run is quite long.

[chippieshaun]

You're absolutely right , Mocki , that it will be a bit of a faff unplugging and plugging in every time you get 240v from a campsite but I'm thinking that i will gain from this modification because the 12v element does appear to be knackered.
I think i saw 12v heating elements for around the £40 mark (not exactly sure) but i can get a inverter for under £20!

AngeloEvs , thanks for the advice.
I was originally thinking about mounting the inverter inside the cupboard to the right of fridge (next to the 240v socket that the fridge plugs into) making it easy to switch between inverter/240v but after what you have explained , i am now re-thinking this!
Am now thinking about mounting the inverter behind the drivers seat , above the starter battery to keep the 12v supply wire from the relay as short as possible and then , like you suggest, run a 240v extension lead behind the units and into cupboard next to fridge socket.

Would this inverter be man enough for the job??

http://www.towsure.com/product/3216-150_Watt_Inverter" onclick="window.open(this.href);return false;

Ta very much for input
Shaun

[AngeloEvs]

Looks OK and will do for the 240V element but for an extra fiver or so I would probably go for a 300W. The 3 way fridge should connect to the 240V EHU via a 13A socket anyway so its just a matter of unplugging it and connecting to the extension lead. And yes, best place for the invertor is behind the drivers seat.

[jaylo264]

AngeloEvs, don't want to bogart this thread but what I tried to do today is kind of relevant --- my kids want ps2 and of course a colour telly , the 150 w invertor tried today won't even run the tv ( rated 50 w ) let alone the ps2 ( also 50 w) .
Did run a ps1 (9 w ) and we had a 12volt 5" B+W tv for it , had that running again today but that is poo now to them of course .
Should I try a 300 w invertor ?
Why does a 150 w not run 50 ? ?

jaylo

[AngeloEvs]

I run a laptop from my 300W 'cheap' invertor without any problems but have never tried a PS2 but seem to remember that other peeps have without any problems. Either your equipment doesn't like the 'modified sine wave output' from the invertor or the output voltage is 'dropping out' due to the way it's connected to the battery, it could of course be faulty or not a particularly good make. Ideally, invertors should be connected as close as possible to the battery. Might be worth posting a new topic and asking if anyone runs a PS2 of an invertor and what model, power rating it has.

[Cruz]

Kids and ps2's etc. Get them a wooden top and tell them they are lucky to have that