Wire for 12v compressor fridge

[bartman]

I've just taken delivery of my Aobosi CR85X fridge (a rebadged Alpicool, confirmed by the specs plate on the back).
I've read on here about issues being encountered with startup of compressor fridges, and the advice seems to add up to fitting 6mm sq wire. However, in the instruction manual it specifies 14AWG for a run of up to 6m (about 2mm sq). For a run of up to 11m it says 12AWG (3.3mm sq). I am all prepared to ignore this and follow the advice for 6mm sq, but I am puzzled by the small size of the wires fitted to the fridge that I would have to join the wires to - I don't have the equipment to find the size, I'll try to add a pic to show it.
My questions are, firstly is that small diameter going to create a bottleneck making it pointless using 6mm sq wire, and secondly how would I join two wires of such unequal diameters?

 

[Chasn]

Using oversize cable will minimise total voltage drop. In any situation where voltage drop might be an issue choosing a size or two bigger than that specified will help. Sometimes electrical devices share a feed from the fuse/ circuit breaker panel and having a second device turned on will add to the load increasing overall voltage drop on that feed.
The only down side is added weight and wire flexibility, neither of which is relevent in your case.

To join wires of differing diameter there are many options. You can use a terminal block. I would solder and heatshrink for a neater and more permanent result.

 

[bartman]

Thanks for the reply. I think I'll go ahead with the 6mm sq. I guess the relatively short length fitted to the fridge will be less of an issue with voltage drop, but it seems to me that it's longer than it needs to be

 

[Chasn]

Voltage drop is proportional to cable length and inversely proportional to cross sectional area. To optimise your system you could cut off the fridge cable as short as possible to minimise the length with small cross sectional area. This is probably OTT but if you have to add cable anyway it is no more difficult to do this. To make it easier to remove the fridge at a later date it could include an inline plug/socket. How close this can be to the fridge will depend on accessibility

 

[bartman]

Voltage drop is proportional to cable length and inversely proportional to cross sectional area. To optimise your system you could cut off the fridge cable as short as possible to minimise the length with small cross sectional area. This is probably OTT but if you have to add cable anyway it is no more difficult to do this. To make it easier to remove the fridge at a later date it could include an inline plug/socket. How close this can be to the fridge will depend on accessibility

Thanks. I have in mind that I need to have a length of loose cable to enable me to get the fridge out should the need arise

 

[wildebus]

Voltage drop is proportional to cable length and inversely proportional to cross sectional area. To optimise your system you could cut off the fridge cable as short as possible to minimise the length with small cross sectional area. This is probably OTT but if you have to add cable anyway it is no more difficult to do this. To make it easier to remove the fridge at a later date it could include an inline plug/socket. How close this can be to the fridge will depend on accessibility

I would go along with shortening the cable if it is much longer than it need be.
It is a similar situation to the Chinese Diesel Heaters where the provide loom tends to be both undersized in terms of gauge and overly long - and the combination results oftenm in a heater that won't start due to 'low voltage' cause primarily by the poor loom. With those I fit a properly size cable and cut the loom off, leaving enough on the heater end to work with easily. I take the same approach on a Compressor Fridge.

As far as connecting dissimilar gauge cables, if you are running a cable from battery to fridge, where you are having to join the cable is the perfect place to add the required fuse protection, and so that takes care of joining cables

 

[bartman]

I would go along with shortening the cable if it is much longer than it need be.
It is a similar situation to the Chinese Diesel Heaters where the provide loom tends to be both undersized in terms of gauge and overly long - and the combination results oftenm in a heater that won't start due to 'low voltage' cause primarily by the poor loom. With those I fit a properly size cable and cut the loom off, leaving enough on the heater end to work with easily. I take the same approach on a Compressor Fridge.

As far as connecting dissimilar gauge cables, if you are running a cable from battery to fridge, where you are having to join the cable is the perfect place to add the required fuse protection, and so that takes care of joining cables

Thanks. I had assumed that the fuse should be at the battery +ve end. I've never used 6mm sq cable before so when it arrives I'll have a better idea of how to tackle it

 

[wildebus]

Thanks. I had assumed that the fuse should be at the battery +ve end. I've never used 6mm sq cable before so when it arrives I'll have a better idea of how to tackle it

You would have a fuse at the battery end, but if you have a longish cable, it doesn't hurt to have one at the other end as well and very often a fuse holder provides both a convenient and cost-effective way to joint different cables - especially ones of relatively large gauge. (soldering a 6mm2 cable properly, as has been suggested, can be no easy task depending on the type of iron you have.)

 

[bartman]

You would have a fuse at the battery end, but if you have a longish cable, it doesn't hurt to have one at the other end as well and very often a fuse holder provides both a convenient and cost-effective way to joint different cables - especially ones of relatively large gauge. (soldering a 6mm2 cable properly, as has been suggested, can be no easy task depending on the type of iron you have.)

I had thought that's soldering might be a bit tricky. What size fuse would be appropriate?

 

[wildebus]

I had thought that's soldering might be a bit tricky. What size fuse would be appropriate?

smaller than the continuous current capacity of the cable. I'd probably go for something like a 30A or 40A on a Midi Fuse Holder at that end. Make it bigger than the fuse at the battery/supply end.

 

[trevskoda]

I have this type which come in low to high ampage.

 

[bartman]

I have this type which come in low to high ampage.View attachment 149231

They look a bit up market, I'll be going for a more Linux type midi fuse.
Oh, and I have a Skoda now

 

[trevskoda]

They look a bit up market, I'll be going for a more Linux type midi fuse.
Oh, and I have a Skoda now

Now im con fused.

 

[YeoBlade]

I have this type which come in low to high ampage.View attachment 149231

Umm, you may not use those after you have watched Will prows YT test on 'em

 

[trevskoda]

Umm, you may not use those after you have watched Will prows YT test on 'em

I tested mine and are very close to stated amps breakpoint, many things you buy these days are not just as stated, ford and range rover cars spring to mind.

 

[YeoBlade]

Thanks. I had assumed that the fuse should be at the battery +ve end. I've never used 6mm sq cable before so when it arrives I'll have a better idea of how to tackle it

6 mm sq really needs the ring lugs crimping, the Yellow lugs from Toolstation are cheap enough and ingenious use of pliers and/or vice will crimp them if you don't have the tool

 

[merl]

Now...I don't like it either BUT If soldering or crimping isn't an option then you CAN make a decent job with terminal block.
DON'T try joining the cables by putting them into the block at either end though.
Trim off about 30mm or more of insulation off both cables.
Hold the two cables side by side and twist the bare ends together.
Push the whole twisted end into an appropriate sized terminal block so the insulation is tight up to the plastic and tighten both screws onto the copper.
Cut off the excess wire that's sticking out the end.
Wrap with some insulation tape.
Looks a bit rough and DIY but it really makes a very good joint because the cables are not only twisted together but also crimped with both screws. Dissimilar cable sizes aren't an issue either.

 

[Caz]

I'm confused by this. My Alpicool came with two leads, a 12v cigar lighter plug is on the end of one and a 230v mains plug on the end of the other. I just use whichever lead plugs into whichever power source is available - in the house it is mains and in the van it is 12v. Why would you be adding more wiring to it? I've not had any issues with it not starting up.

 

[bartman]

I'm confused by this. My Alpicool came with two leads, a 12v cigar lighter plug is on the end of one and a 230v mains plug on the end of the other. I just use whichever lead plugs into whichever power source is available - in the house it is mains and in the van it is 12v. Why would you be adding more wiring to it? I've not had any issues with it not starting up.

My fridge is the same as the Alpicool CR85X, and there is just one input wire which can be a supply of 12 or 24v. Total capacity for fridge and freezer compartment is 83l. I'm guessing that your Alpicool is a different model.
I've just got it up and running today, wired directly though to the battery. All is well, so a big thank you to all who helpfully responded to my questions.

 

[trevskoda]

I'm confused by this. My Alpicool came with two leads, a 12v cigar lighter plug is on the end of one and a 230v mains plug on the end of the other. I just use whichever lead plugs into whichever power source is available - in the house it is mains and in the van it is 12v. Why would you be adding more wiring to it? I've not had any issues with it not starting up.

Most cigy plug outlets in cars/vans can only handle 10 amps, i had a 200w screen heater and it melted the cigy plug, took me a while to work out why.
About 150w max through ciggy socket.