Did I do something wrong with solarpanels?

Oct 25, 2018
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So we've brought a solar kit by eco-worthy 200w 12v/24v but they don't seem to be charging our battery properly by that I mean I plug a 85w mini fridge and within 40mins the 1000w bestek inverter will go to red light and the battery will be on 1 bar on the anself 10a/20a charge controller.

Is there something wrong as the battery is 75ah but lasting nearly nothing is the charge controller not using the entire battery? Any help would be very much greatful thank you.
 

Parksy

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Nov 12, 2009
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I doubt if your solar panel would power your fridge on battery or add enough charge to allow your fridge to run from battery via an inverter.
I've no doubt that somebody clever will be along soon to explain the maths but in my experience solar panels only trickle charge your leisure battery even in bright sunlight and an inverter will be power hungry which wastes battery power.
If you wanted to use the caravan fridge it works best off grid using LPG
 
May 7, 2012
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I have to agree, fridges draw a lot of power and a solar panel is unlikely to be up to the job. The Prof has recently written in detail on the power draw on the subject Caravan Battery, which has more information than i could give.
 

JTQ

May 7, 2005
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I hope some rough numbers help in understanding the issue here:
At the very least your 85 W mini fridge will be pulling something around 7 Amps, by the time that hugely oversized inverter takes its cut, it could be a 10 Amps battery drain.
Your 75 Ah battery if in great condition is good for up to 50% of its rating, unless you plan for a very short life from it.
So, in the battery's first flush of youth and starting fully charged, there could be 37.5 Ah available before we consider the solar panel; so the battery could last 4 hours with nothing else at all on, if the fridge is running 100% of the time. Therefore zero chance of getting through the night from fully charged and new.
The 200 W solar panel will give you zero output all through the night. This time of the year, even pointing at the sun and you keeping moving it around, on a shadow free pitch, you would be lucky to see over 11 hours, a yield of a third of its rating.
Say, on a good day 200 x 11/3 = 730 Wh, so about 60 Ah, so that could last the fridge alone another 6 hours.
Therefore in 10 hours from a full battery to a flat one, assuming you started off in the morning; however there are 24 hours in the day and far from every day is good and sunny all day or many pitches shadow free. Plus treating the battery like that its ability to accept a charge anywhere close to its labelled value, will be tumbling away rapidly.
The system is not adequate, you need a different fridge solution.
 
Sep 26, 2018
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Peltier effect refrigeration is useless for 12v. In the marine environment we mainly use compressor fridges/coolboxes. These draw the same current... BUT... they switch off when the fridge is cool enough and only switch on again when it's warmed above the temp setting... on mine on the boat this means that the compressor runs about 5 mins every half hour, which equates to (say) 10 minutes of 7A per hour, or about 1AH... Over 24 hours, that means a 70AH battery WOULD cope as the consumption is 24AH per day.

On the boat, we have 330AH of battery capacity and 200W solar panels, we are self sufficient for well over a week.
 

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