Thread: Upright Compressor Fridge - Solar

Garry, quick answer is that it's preferable to run as much as you can through the "load" terminals of your MPPT controller, as opposed from the battery directly.
***EDIT*** the above is true EXCEPT for large, short-term loads, such as running compressors or inverters drawing a large current ***

I've just gone through a huge learning process regarding Solar, charge controllers, and their optimum usage.

After a lot of research (and there is a LOT to read out there), I found this web page was the most useful to me in understanding how this stuff works:
Design Guide for 12V Systems

From the "Solar Regulators" section onwards (the "Overcharge..." section details using via the load outputs on your controller vs straight from the battery) was most useful for me, though there's a lot of useful information before that as well.

I'm sure somebody far more knowledgeable will be along shortly to confirm or contradict me - good luck!

Garry, is it another ebay fridge , been looking at some of those uprights that i think would be great in a kombi.

Originally Posted by TeamFA

Garry, quick answer is that it's preferable to run as much as you can through the "load" terminals of your MPPT controller, as opposed from the battery directly.

Thanks for that - the main fridge needs to run from the battery. I take the point in the article about overcharging the battery but in reality any extra juice the MPPT is putting into the system is being used by the fridge compressor when it is running - depending on how full the battery is, as soon as the compressor switches off the MPPT goes straight back to float.

Originally Posted by loanrangie

Garry, is it another ebay fridge , been looking at some of those uprights that i think would be great in a kombi.

Yes - this one 50L Portable Freezer Fridge 12V 24V 240V Camping CAR Boating Caravan BAR Fridge | eBay

Is Ok - freezer in not fully enclosed and door is very flimsy but seems to be OK for the money. Uses 50% more power than my normal 55l ebay chest fridge but it has a lot thicker insulation. When I put it in my camper I will pack a lot more insulation around the outside.

Garry

Slightly off topic sorry...

One thing I considered between upright and chest power usage is that hot air rises and cold air falls down. As soon as you open an upright fridge you will lose a heap of cold air out the bottom. Not sure how big the impact would be, but we all know a fridge uses less power when it's left closed... That maybe exaggerated with an upright over chest.

Back on topic, I don't have anything connected to the "load" terminals. Found them a bit pointless for everything I wanted to do. I'll have a read of that link shortly and see if I can learn something!

Originally Posted by TeamFA

Garry, quick answer is that it's preferable to run as much as you can through the "load" terminals of your MPPT controller, as opposed from the battery directly.
***EDIT*** the above is true EXCEPT for large, short-term loads, such as running compressors or inverters drawing a large current ***

I've just gone through a huge learning process regarding Solar, charge controllers, and their optimum usage.

After a lot of research (and there is a LOT to read out there), I found this web page was the most useful to me in understanding how this stuff works:
Design Guide for 12V Systems

From the "Solar Regulators" section onwards (the "Overcharge..." section details using via the load outputs on your controller vs straight from the battery) was most useful for me, though there's a lot of useful information before that as well.

I'm sure somebody far more knowledgeable will be along shortly to confirm or contradict me - good luck!

At a PC now. Great site, although I can't find the bit on regulator load verses direct to battery connection?

Originally Posted by Judo

At a PC now. Great site, although I can't find the bit on regulator load verses direct to battery connection?

Go down to the section titled "Overcharge from DC-DC Converters and Solar Regulators".

Originally Posted by Judo

One thing I considered between upright and chest power usage is that hot air rises and cold air falls down. As soon as you open an upright fridge you will lose a heap of cold air out the bottom. Not sure how big the impact would be, but we all know a fridge uses less power when it's left closed... That maybe exaggerated with an upright over chest.

You are quite correct but with a "full" upright the difference is probably not all that noticeable and the contents will quickly cool the air. Notice all household fridges are upright and so are the majority of those in caravans.

The fridge I have is going into a camper van to replace a 3 way upright. It will mainly be used to hold ready use items like marg, fruit, drinks and icecreams . I also use a standard 25l or 55l chest camping fridge for the longer use stuff.

This was a major consideration in going to a 2 way from a 3 way as there will be double the 12v power requirements but as I am upgrading battery capacity and solar capacity anyway should not be such an issue.

Garry

My Solar panels came with this controller glued to the pack of the panels
CMP Solar Panel Charge Controller Regulator 10A 12V 24V Auto Identify Black | eBay

This system is generally derided but did seem to work.

In view of various reviews I "upgraded" my controller to this MPPT controller bought at a 4wd show MPPT 30A Solar Controller Regulator 12V 24V Auto Switch Battery Converter AU | eBay

When I have used this controller it never gets over 5amps at the battery which I put down to a nearly fully charged battery. On a good day it matches the power drain out of the battery but not enough to make up for the drain oversight - I guess it is the smart charger doing its thing and doing what is best for the battery and not just getting as much juice in as quickly as possible - the problem is the sun goes down before the battery gets totally full.

I started using the battery yesterday at midday and by midday today the fridge had pulled 20 ah but the solar had only put in 16, so in a 24hour period I am slowly draining the battery despite the panels being in full sun.

So I disconnected the MPPT controller and connected direct to the panels and the Watt Meter showed 6 amps charge (double the MPPT input) and 13.7v (noting I think this is a mix of battery voltage and solar panel voltage (17-19v). Within one hour the solar panels had made up the overnight loss and output had matched input and switched back to using the MPPT controller.

So my concern is that instead of keeping the battery conditioned and topped up, my MPPT controller is strangling the system a bit and when you take the day night cycle the battery will slowly drain despite there being full sun.

So am I expecting too much or do I need a different controller - one that more oompf back into the batteries before it goes into float.

Cheers

Garry