Thread: Inverter versus 12v

It was a Samsung unit - will put a link up tonight when I’m at my computer.

Just seen this thread so I apologise if it's been thrashed to bits already. IMHO it is always better to use 12V direct rather than through an inverter. Unless there is amazing new technology - which is always expensive - inverters gobble an awful lot of power whether they are feeding a unit or not. Can expect a 1A draw with no load. As the fridge is expected to cycle for a few minutes at a time with long periods of rest that amounts to a lot of wasted battery resource.

Originally Posted by Tinggu

Just seen this thread so I apologise if it's been thrashed to bits already. IMHO it is always better to use 12V direct rather than through an inverter. Unless there is amazing new technology - which is always expensive - inverters gobble an awful lot of power whether they are feeding a unit or not. Can expect a 1A draw with no load. As the fridge is expected to cycle for a few minutes at a time with long periods of rest that amounts to a lot of wasted battery resource.

Better quality inverters (e.g. Selectronic) go into sleep mode when not under load and draw bugger all power.

I carry 2x inverters, a small one I think it is only 200-300w that I use to power or recharge my laptop and a larger 2kva unit I carry in case I need to do some emergency welding on the track and this has come in very handy on the Useless Loop road sticking my boat trailer mudguards back on that the corrugations are determined to remove.
I have used both inverters when camped up and the smaller unit doesn't seem to drag too much out of the batteries, The 2kva unit however is pretty power hungry so it obviously isn't one of those units that will power down when not in use.
I imagine that these new inverter type fridges would come with a fairly small inverter that powers down when not in use But is there any Real advantage using these types of fridges over a normal 12v/240v fridge?

Originally Posted by bee utey

Better quality inverters (e.g. Selectronic) go into sleep mode when not under load and draw bugger all power.

Yep, I have a Selectronic unit - brilliant bit of kit. Once the load drops below a pre set load - mine is selectable between 4, 8, 12 and 16 Watts for 15 seconds, it goes to sleep and uses around 50mA when asleep. As soon as a load is applied it kicks back in instantly. When I’m out in the van, I never turn it off - it does it all for me.

It’s the cheap Chinese units you need to watch out for.

As others have said

Use a 12v fridge with a reputation for efficiency.

Inverters have losses, that is why they have cooling fans, and unless they are the type that goes to sleep, draw power even when no 240 power is being used.

I am getting an inverter wired into my camper trailer, and it will be turned on by a switch beside the inverter power point, with a warning led to show it is ON. The switch operates a relay to provide power to the inverter. The intent is to only have the inverter powered when we need power at the power point. Some larger inverters come with a remote switch, but a basic relay will do the same job.

If possible, add extra insulation in the fridge cabinet on the sides to minimise heat flowing in through the fridge walls. Also ensure that the fridge condenser is well ventilated. Heat buildup around the condenser both increases heat inflow which makes the fridge cycle ON more, and also reduces the refrigeration cycle efficiency. A recent study of household compressor fridges showed that power consumption tripled when “room” temperature increased from 20 to 40 degrees C. That is around a 15% increase in power usage for each degree hotter. If you can add a small computer fan of say 3 watts to assist the convection flow up the back of the fridge and out, that comes on with the compressor, the small extra power used by the fan will significantly reduce overal fridge power usage.

As the other guys have said:
Less efficient electrics as no need to be so careful with power,
Poorer insulating techniques as no need to be so careful with power,
Large electrical losses in the inverter, converting ELV DC to LV AC.

Also further mechanical and heat (ie energy) losses in the fridge motor if the inverter is a ‘modified square wave’, as the ‘sharp edges’ create magnetic eddies and mechanical jitter etc etc. (the mech is probably too subtle to be felt by us, but you can feel the heat)

But also, I understand that the domestic fridge motor is not designed to cope with non-level or moving operation. The fridge fluid slops around the sump, doesn’t lube the pump properly, or allow smooth or proper pumping.

Thats why certain portable fridge makers extol the virtues of ‘swing’ motors etc.

Hope this helps,
cheers

Originally Posted by DeanoH

Had a chat with another Oka owner today and he was extolling the virtues of inverter fridges. It seems that inverter fridges (as in inverter air conditioner technology) are being made now by LG/Samsung for example and are reputed to be very electrically efficient.

Deano

I have a Samsung Inverter fridge in my house. No idea how much power it has saved, but after around 18 months there has been no problem with it. The inverter has a 10 year warranty and it cannot be heard running.

These units are VFD, the same as a room air conditioner. SOME of them can be run off a 240 volt external inverter, but NOT all of them. Beware!

How the Digital Inverter Compressor Has Transformed the Modern Refrigerator – Samsung Global Newsroom