Solar Fridge Help

[arniesab]

I have a Unique 10.3 cu.ft. 12 V. DC fridge (pulls 53watts, 524wh in 24 hours).
According to the manual, I should use 8 Gauge wire for the 30foot run. It also says a "15amp fuse should be installed in-line near the battery terminal" (and that it's included--but it is not). My system is pretty basic. 1 Lithium 100AH battery. 500W of panels. Victron 150/35 controller.

My question: I have the 8 gague wire going to the battery terminals directly, as recommended, but I'm confused about what size in-line fuse to use. For 8AWG wire, I don't find any 15 amp fuses (and it seems that that size wire requires a 40Amp fuse). Should I install a 40A in-line fuse near the battery terminal? Or, should I rethink how to run a 15A fuse on the line (fuse box?). I'm very new to solar and any help/advice appreciated.

A further concern: I attached the 8AWG wire to the 4 feet or so of wire coming out of the fridge, which looks to be 12AWG at best. Is that OK, or should I run the 8AWG directly into the power supply under the fridge?

Thanks!

 

[BentleyJ]

Something like this? Not a budget solution but looks like the lugs will take the #8 wire.

Bussmann by Eaton - CHPV1U - Fuse Holder, 30A, Rail Mount, For 10 x 38mm 1000 V dc - RS

CHPV1U from Bussmann by Eaton at RS

us.rs-online.com

 

[arniesab]

Thanks, yeah, I've looked at some things like that. I'm wondering if I really need a 15A fuse, as recommended by the manufacturer, or if that size fuse was assuming you just used the stock wire coming out of the fridge and didn't extend it 30' with 8AWG wire.

 

[BentleyJ]

Thanks, yeah, I've looked at some things like that. I'm wondering if I really need a 15A fuse, as recommended by the manufacturer, or if that size fuse was assuming you just used the stock wire coming out of the fridge and didn't extend it 30' with 8AWG wire.

The over current protection rating of 15A doesn't change due to distance. The wire gets bigger to minimize voltage drop at that given operating current. The problem comes in with long distances where the wire gets too big to fit in the lug of the breaker or fuse holder.

If the appliance is only pulling 53W at 12V that would be about 5A. Using the Southwire calculator, #8 wire would have a 1.7% voltage drop which is only 0.2V.

 

[mikefitz]

You need a 15 amp fuse, although the running current is around 4 amps, the start current is much higher. Although you have 8awg feeding the fridge, the fridge electronics wiring is a much smaller gauge, that's what the fuse is protecting, along withe the 8 awg cable. The fuse should be as near the battery as practical, as should any over current protection in a battery powered system.
Don't try to connect the 8 awg direct to the fridge electronic pack, its terminations are delicate, make a connection to the existing 'tails' supplied with the fridge.
The fridge electronics are sensitive to voltage, thus the requirement for heavy gauge cable to minimise the volt drop.
Use an inline fuse holder,

Amazon.com : 12v inline fuse

Or a fuse box, this will also alow connection of other loads or chargers to the battery,

Amazon.com : 12v Fusebox

Note the fridge instructions cover the use of lead acid batteries that have a lower nominal working voltage than lithium and a greater voltage 'sag' under load. This is why the recomended cable seems 'overkill'.


Mike

 

[arniesab]

Thanks. Very helpful. Any suggestions on how best to add a 15A fuse between the 8AWG wire and the batt. terminal? Will I need a small DC fuse box?

 

[arniesab]

Sorry, didn’t see your links to inline fuse holder. One more question: can I use an 8 gauge inline fuse holder like the one listed above, but just swap in a 15A fuse instead of the 40A fuse that comes with it (which would make it a little easier to connect to the 8AWG wire)? Thanks again!

 

[mikefitz]

Any suggestions on how best

Made additions to my post, use whatever is most convenient. OK to swap the fuse.

 

[Johno1066]

Are these 12 volt refrigerators based on the Danfoss BD 50 compressor with the module that converts 12 volt DC to 3 phase AC?

 

[arniesab]

Yes it has a Danfoss/Secop compressor.

 

[740GLE]

The other thing to keep in mind is the conductor size is primarily based off FLA, not lithium. These fridges have been around for ages.

FLA have pretty good voltage sag with load, where as lithium is rock solid.

IMO 8awg is totally over kill with Li.