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3833 posts

Uber Geek


#304229 15-Apr-2023 16:05
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My jaycar 12v fridge stopped cooling so decided to get a new one.
Brass Monkey GH2068  


I see they now have a few options with lithium battery packs and solar panel inputs.    


I have a 180w panel on the ute so thought this would be quite nice - I could get rid of the deep cycle battery.   


The one i bought had a fault and wouldnt accept any current in from the solar panel, so I was able to swap it for another one back at the jaycar shop. 


The manual is pretty poorly written but extra info I worked out 
 - The DC barrel jack accepts a solar panel up to 50v 
 - Tip positive / Ring Negative   
 - Its only a built in PWM solar controller. Not MPPT.   


This means my 180 watt solar panel on the ute is only capable of charging at a peak of about 60 watts on a sunny day. Sounds like I'll need to get it put back running via the deep cycle battery and mppt controller.    


If you are looking at getting one of these with a solar panel, you would be best to get two smaller panels of no more than 120w each rather than one larger one.
Once you go above 120w the panel output voltage tends to increase, which any gains are then lost via the PWM controller, while the amperage stays the same. 


So if you can get two 100 watt panels, you will increase the total surface area for energy collection and offset clouds on an overcast day if you connect them in parallel. 


This PWM issue has been a big disappointment for me.    




The bluetooth is really nice - the app works reasonably well. 


Everything else seems really good. 




So I am going to leave it directly connected to the solar panel for a few days to see how it goes but its overcast and not even charging at 15 watts right now or and definitely not able to keep up with its consumption.
Normally the panel it would be doing 80-120 watts on a day like this via the mppt controller.    


It uses about 60 watts on max mode when the compressor is running. The manual says about 0.2kwh per day (16ah at 12v) but if its anything like my last Brass Monkey fridge, it will be more like 3-4x that when its under some shade in the back of the tray/canopy on a warm day. 


I did run it on the 12v all day yesterday and got it cool enough for ice to form in the water bottles, and the ice bricks (thermal battery) were solid but melted overnight. So the insulation is not good, like the last one. 


So these are great if you do have a constant source of power, or a larger external solar system to keep it powered.    


Posting here to document what I found - the instruction manual didnt specify the solar input polarity so I ended up working it out with a continuity test - ring on the solar barrel input (stupid choice of connector - up to 10amps really???) is bonded to the negative 12v input but only via the battery. 



Ray Taylor

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768 posts

Ultimate Geek

  #3063946 15-Apr-2023 17:21
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Thanks for the documentation, helpful as the details are pretty scarce online and have been looking around at these and similar


Lenovo computer and accessories deals (affiliate link).

3833 posts

Uber Geek


  #3064276 16-Apr-2023 12:50
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Managed to find an interesting trick. 


An EPEVER AN series controller seems to be able to tricked into booting up without a battery on first. Normally the battery is needed so the solar controller can turn on, detect its operating 12/24 voltage and then start accepting power from the panel. 

If you have a load present, and no battery, it appears to still boot up into 12v mode and starts power tracking when you apply solar power. I have managed to get it to do this several times but will see how it works overnight with a slowly fading sunset/sunrise.  


I am going to swap it for a 10amp model as they are self limiting - they wont do any more than 10 amps in/out even if you apply/suck more power which means i hopefully wouldnt go over the 10 amp limitation of the solar input on the fridge. 
Its overcast today so unlikely to get up to 10amps before the battery is fully charged and the compressor only draws 4 amps.
The battery discharge protection is set high so as soon as the sun goes down, the compressor  will switch off soon after so the battery doesnt discharge much overnight. As the sun rises tomorrow morning, even if its clear sky, i would expect the battery to be fully charged again before the panel is in full sun, by which time the compressor will only be drawing about 4 amps. 


Tomorrow I might also try it on the 12v input as that can accept a higher amperage, bypasses the controller but i am not sure how it will perform with the varying amperage going in via the 12v input where its probably expecting a constant 6 amps to be available at 12.8v off the vehicle. 




Ray Taylor

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