Inverter overload

[David Killough]

Hey everyone,

I've got a Mobitronic (waeco) 600w inverter that is powering my Tristar supercool 45 fridge. The inverter output is 230v at 50hz and the fridge runs at 230v at 50hz. The inverter is powered from my dual battery system and is connected to a 3rd battery in the back for operation when the motor is off. My question is this. Why would my inverter be going into overload? I'm no electrician, but then again, it was setup like this when I bought it. I do have the inverter mounted sideways on my rear drawer system. It's tucked under one of the wings, but there is still plenty of room for cooling. Any ideas???

David

 

[Chris]

Almost exactly the same as my set up. Mine doesn't over load. And I run a 550W angle grinder off mine. Sure it's not the low supply alarm?


Chris

 

[David Killough]

Chris,

There's definitely a buzzing that goes off, but I've also noticed the fridge stops cooling too. Not sure if it's drawing touch power or if the battery is flat or what... I'd think with the dual fronts running to the back also charging battery #3 there wouldn't be much issue. Is the inverter under powered for the job??

 

[uHu]

Doesn't look like much cooling there for sure. It's not enough with space around the inverter. You need circulation as well.

Put a voltmeter on the input, so that you know what voltage the battery is feeding it. If you draw 100 watts, it will suck 10 amps from the battery, presuming 80 % efficiency including cable loss.

Small voltmeters like this are cheap, take little space, and are easy to install. Put one for each battery, at least.

http://dx.com/p/mini-3-digit-blue-displ ... 30v-147222

 

[David Killough]

uHu,

I thought about putting a little fan into that wing for circulation purposes. Still not sure. The battery was tested today and is holding over 12v under load. The volt meters sound nice, but I'm not really in a place to add those. I'm on the Namibian/Angolan border and will be crossing into Angola tomorrow. I'm trying to figure out if I can fix this before leaving Namibia.

 

[SpinDrift]

Does the alarm go off as soon as you start the engine or maybe when the split charge unit kicks in? If so it could be the sudden surge to the inverter which is in a loaded condition that is causing the alarm to go off. You could try starting the engine and waiting until the split charge unit kicks in before plugging in the fridge.

You might also want to try running the inverter with the lid of the cubby hole open / removed so air can circulate, to try to eliminate the overheating theory.

 

[Graham]

Hey everyone,

I've got a Mobitronic (waeco) 600w inverter that is powering my Tristar supercool 45 fridge. The inverter output is 230v at 50hz and the fridge runs at 230v at 50hz. The inverter is powered from my dual battery system and is connected to a 3rd battery in the back for operation when the motor is off. My question is this. Why would my inverter be going into overload? I'm no electrician, but then again, it was setup like this when I bought it. I do have the inverter mounted sideways on my rear drawer system. It's tucked under one of the wings, but there is still plenty of room for cooling. Any ideas???

David

.
Definatly lack of cooling air.
Perhaps fit a small 75mm panel fan, what are commonly seen on electrical cabinets?
.
[attachment=0:2aug24x9]panel fan.jpg[/attachment:2aug24x9]
.
When I first seen your build, a while ago, I knew then you may run into cooling problems, but never mentioned.

Gra.

 

[David Killough]

Hmmm... Seem to be having trouble posting.

I did what Spin said. Started the engine, turned on the inverter without the fridge plugged in. I let the truck warm up for a few minutes then plugged the fridge in. In ran fine for about 10 min. Then the alarm began to buzz. It wasn't showing the overload light and the wing was open for cooling. The inverter was cool to the touch and it was a cool morning. Any ideas what is going on???

 

[Chris]

David, I am no elecktrishun so you can tell me to boil my head in a bucket at any point, but having read back, you seem to have one of those three way fridges? Like the Quest? Gas, 240 and 12? If not then don't read any further.

If you have them my experience was that they were massively power hungry. The gas was brilliant but not on the move, eh? The 12v just about kept it cool if really well chilled and the mains was great - when plugged in at home. What the 240v does in effect is step down to 12v (I think) so you are taking 12v, turning it into 240v then stepping back down to 12v again which has to be incredibly inefficient. With a posh fridge like a Waeco or Engel, the efficiency is incredible. And they work fully from 12v, not just hold. I rather think that the issue here is the fridge. I had pretty much the same problem with mine when I had a cheap inverter linked up to run the Quest. It ran for an hour and then was done. The inverter should be fine, the battery should be fine, but the fridge is just inefficient and is flattening the battery faster than you can charge it. The battery won't be flat it will just be below the level that the inverter will run from. If you ran the fridge on 12v from the battery directly it might go until the battery was flat as there's no voltage protection in there. But the inverter is protecting what's left in the battery so that you can start an engine from it. You won't be able to get past that barrier. On a Waeco etc you can set the terminal voltage at which you want the fridge to switch off.

Chris

 

[Gary Stockton]

Given where you are, and it's winter there still, summer you're going to have an even bigger issue. Dump the fridge and try to get a proper 12v WAECO, National Luna, Engel, Minus40 or similar from LA Sport or Safari Centre in Windhoek - or a 2nd hand one on Gumtree or something. Don't think your current set-up will survive +40 degrees every day in summer. OK for a static set up off mains, though.

Probably not what you want to hear, but I suspect it'll save you pain and heartache (and pennies) in the long-run.

Cheers

 

[Graham]

I bought one of Paul's 2000 watt inverters.
It is not encased in any shelving, and runs well.
It powers a 240 volt 50 liter freezer, and a 240 volt 50 liter fridge.

Rated at 2000 watts, I guess the total loading when the fridge and the freezer are both running might be 170 watts.
The inverter get marginally warm on 40 degree Spanish adventures.
It does have more than enough ventilation, plus it's own integral variable speed fan.

The fridge and the freezer have done thousands of miles, touch wood, without problem.

When we get to a camping site, we use an extension lead, and use "shore power"



Gra.

 

[David Killough]

Chris,

You are right. I do have a three way fridge. I've just now plugged it into the 12v socket that is wired into the back. It uses heavy gauge cable do hopefully that'll help.

Basically my only option then is to either use the 12v socket and get by or get a better fridge made for overlanding. The inverter is a waeco unit, so it shouldn't be the problem right??? I imagine the battery is now flat and needs a good day of charging uninhibited off the truck. Does that sound right?

I'll let you all know how the 12v socket does with cooling duties. Another fridge isn't an option right now, but maybe in the near future.


If anyone else has some thoughts, I'm all ears.

David

 

[Chris]

The 12v essentially runs the fridge in a different way. And it just holds temp if you are lucky whilst on the move. As Gary says in a hot car it will be next to useless. The 240v system will be on overtime. Best option in those conditions is the gas which is awesome. I have driven with it on gas. There are so many fail safes on the regulator and the fridge that it's pretty safe really but not the best I guess. The reg must have a cut off. Gav had the same fridge and ran it without a safety reg if I remember right and he had a bit of a tent fire when the gas came out of the bottle through a hole in the pipe. The reg has a valve which shuts if the gas come out too freely. The gas flame on the fridge is just a tiny pilot light. I have run with a window open. You aren't going to poison your self. You could run in 12v then switch to gas every time you stop to get it good and cold again.

But Gary is right really.


Chris

 

[David Killough]

We won't be her for the summer, just 4 more weeks and the a/c in the truck is awesome! My mate who will be traveling with us has a Conqueror Commander. I bet I can plug it into his power at night and use my 12v plug while on the road. Not ideal, but it'll do for this trip. Next time I'll have a better fridge and setup some improved cooling for the inverter.

Question on the fridge/inverter note. How many watts can I expect a 50l fridge to pull? Is my inverter sufficient for the task?

 

[Graham]

We won't be her for the summer, just 4 more weeks and the a/c in the truck is awesome! My mate who will be traveling with us has a Conqueror Commander. I bet I can plug it into his power at night and use my 12v plug while on the road. Not ideal, but it'll do for this trip. Next time I'll have a better fridge and setup some improved cooling for the inverter.

Question on the fridge/inverter note. How many watts can I expect a 50l fridge to pull? Is my inverter sufficient for the task?

.
The ones I bought run at about 50 watts when they settle down after "kicking in"
It is a fair "kick in " current though, probably an instant of 300 watts for the first 2 seconds.

This is the sort I bought, but not this make, I think they were Beko? not sure.
.
[attachment=0:1qkbgix7]fridge.jpg[/attachment:1qkbgix7]

They both look identical, and sized the same.
The fridge and the freezer were both about 450mm High x 500mm wide x 500mm deep, or some thing close to that.

Be quick £10.50 with 4 hours left small fridge on Ebay

Gra.

 

[Chris]

Wow Gra, that's like a proper domestic fridge. I'm sure that the dedicate car fridges pull less than that. On 12v mine will run close to freezing for nearly a week on my leisure battery. There is no advantage to running it on 240v from the inverter as all it does is convert that back to 12v again. I guess that handsome one of yours is running 240v with no step down.

Chris

 

[Graham]

Yes you are right Chris.
Just a plain and simple 240 domestic variety.
When we have no "shore power" of an evenings I just switch them off for the night.

No difference by morning, as the door doesn't get opened.

Gra.

 

[David Killough]

Well guys, I found out something at the very end of my time in Angola that made me sick. There is a emergency power cut off "key" that goes into a port that looked something like a 12v outlook. It turns out that because I wasn't aware of this fact, the alternator was never charging the 3rd battery. This caused the fridge to drain the battery quickly. The inverter was never the issue. The fridge runs fine now with the emergency power cut off key in. Thanks for all the options and support!

 

[Chris]

C

 

[David Killough]

Chris that's exactly how I felt...