Comparing Solar Power In Summer And Winter ..........

My original post made some assumptions, one of which was that a horizontal solar panel and it's controller would be capable of charging a battery from sunrise to sunset.
At midsummer day here at approximately latitude 52° sunrise is at 04:42 and sunset at 21:24, resulting in a day length of 16 hours 42 minutes. Unfortunately I don't have a screenshot of the solar charger output on midsummer day to allow comparison of daylength and charging time, but do for the Autumn Equinox:

View attachment 57923

As can be seen, the system was charging the leisure battery for 12 hours 48 minutes at the Autumn Equinox.
On the equinox one would expect 12 hours of daylight at pretty much any latitude, but there are several different ways (surprisingly!) of defining these things and using the definition I've used, sunrise was at 06:46 and sunset at 19:01, giving a day length of 12 hours 15 minutes.
There's reasonable agreement between daylength and charging time at the Autumn Equinox.

On midwinter day here at approximately latitude 52° sunrise is at 08:06 and sunset at 15:52, resulting in a day length of 7 hours 46 minutes. The solar system data on midwinter day was:

View attachment 57921

As can be seen, the solar system was charging for a total of 7 hours 3 minutes.
Again, there wasn't bad agreement between daylength and charging time.
On midwinter day the weather here was appalling with dark skies which means that the only solar energy reaching the solar panel was light scattered by thick cloud - so the light intensity was much attenuated. This would affect the start and stop times of the solar charger, resulting in reduced overall charging time.

In summary the assumption I made in the original post was reasonable to a first approximation.

Colin 🙂🙂🙂
Am I missing something, it looks like your claiming to charge already charged batteries?
 
Am I missing something, it looks like your claiming to charge already charged batteries?

The solar panel and controller are constantly monitoring the condition of the batteries and making good any discharge, whether that discharge is intentional or not.
I posted something on this topic a while ago:


I hope this helps.

Colin :):):)
 
Reading through this thread with a great deal of interest and it amazes me the detail monitoring some members log and use to improve their solar setups.
In layman's terms what I have found using my system which is 200 amps of batteries, 210 watts of solar and a Victron mppt controller is no problems with maintaining battery charge spring and summer when I don't need much charge as not running heating and lights and not much tv but crap in the autumn and winter when I need it lol.
So always carry my ever reliable Honda generator 😁😁😁😁😁😁.
 
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lol Baz, i just posted on a thread on WC to say where I am today it has been overcast and wet all day and best I have seen coming in is 4W off 300W of panels. Thats North Yorkshire
Sound right BUT i know you have a plan B I have rigged spare panel to charge a spare battery some days not getting enough to power the mppt controller , I have rigged up a monitor so no guess work , in perfect sunshine panel facing the sun I got 4.4 amps for a few minutes, Bazz
 
lol Baz, i just posted on a thread on WC to say where I am today it has been overcast and wet all day and best I have seen coming in is 4W off 300W of panels. Thats North Yorkshire

Charlie summed it up years ago quote solar in the winter is a much use as a chocolate fire guard.
 
My new toy tells me my batteries are at 13.08v at the moment, 0800. By midday they will be back to 13.8. Same every day.
This would change, IF I COULD USE IT. Sorry for shouting. But I’m, Bee Oh Are EE Dee. In the extreme.
 
On EHU but solar doing better than expected on this overcast day from our flat 120w panel, I guess the light is reflecting off the full white blanket of cloud so maybe better than if it was clear?
Screenshot_20210119-110740.jpg
 
before i came out at lunchtime my 300W was jumping between 9 and 11 watts. was chucking it down though
 

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