Solar charging - can it be so?

[obiwancanoli]

I'm still trying to wrap my head around the solar and power issue, but I have learned a lot. In conversation with my RV service tech, an independent guy who takes pride in his knowledge and work, I was listening to him discuss the wiring issue, in conjunction with a new Victron controller (100/50) and Victron 712 Voltmeter he'll be installing this week.

Something my tech said about properly wiring the solar panels - in series, I think - got me to wondering...., rather than the alternative setup, pretty much has a good 5-hour window (10-3) for maximum charging, where in series would allow the panels to begin charging as soon as daylight hits, albeit at a lower rate, of course.

I've always heard that maximum performance of any solar panel was generally limited to the most direct sunlite one can have - about 5 hours. And clouds, trees, buildings, etc., severely reduce their capabilities, if not altogether eliminated them.

Now I'm thinking I heard my tech say that properly wired, panels would recharge batteries as soon as daylight appeared, and through the day until dusk, and I assume he said this knowing a new Voltmeter and MPPT 100/50 Controller (Victron's) would also be installed. He also stated he'd seen solar charge batteries sitting under a flourescent light!

Could it be true?!?!?!

[pianotuna]

ajriding wrote:
I would rather have 15 volts with a lot of amps, than 20 volts with a weak amp supply.

Most nominally 12 volt panels put out 17 volts.

My panels are lower than most at 16.5 volts. The seller recommended doing series with an MPPT controller. I did follow that excellent advice.

Solar panels are considered to be constant voltage device. Higher voltage leads to less line loss (l% is great).

[ajriding]

so,
the panels will put out a constant voltage but the amps change.
In shade they still put out the same voltage, or does that drop? I have only experimented with different angles, not with shade.
If you have two 12v panels putting out 18 v each, 36 total in series, and going into a controller that will bounce the volts down to a lower number 13-14v, then all the shade is really doing on the battery side is reducing amps, not volts, since volts get changed anyway.??
no matter series or parallel, it seems the output is going to be decreased by the shaded cell, not the whole panel. I dont think I understand it fully.
I would rather have 15 volts with a lot of amps, than 20 volts with a weak amp supply.

[CA_Traveler]

red31 wrote:
For me the purpose of a controller is to limit power going to a battery (trailer storage), that and 'sleep' or night mode were it prevents batt drainage. 'Full by noon' means the controller was limiting power before noon and the rest of the day unless you have some other use of the excess power.

In active use many things limit power, location, calendar, orientation, temperature, overcast, smog, shade, bird poop, dirt ...

Once the batteries are full the unused solar power is available for house loads, ie keep the batteries full until sunset. Some have used the excess power for say hot water but I'm not sure how well that works out.

[pianotuna]

obiwancanoli wrote:
I'm still trying to wrap my head around the solar and power issue, but I have learned a lot. In conversation with my RV service tech, an independent guy who takes pride in his knowledge and work, I was listening to him discuss the wiring issue, in conjunction with a new Victron controller (100/50) and Victron 712 Voltmeter he'll be installing this week.

There are occasional reports of voltage happening from moonlight.

My system from 1992 (30 watts of amorphous solar for $1700!) would show voltage if I parked under a street light.

My current system does not show voltage when I park under a street lamp.

I believe series installations may start charging sooner in the day. But I have no proof of this, just anecdotal incidents.

Excellent equipment choice on your part. Get the voltage up as high as you can. Then wire the panels in series/parallel.

I would have chosen SiO2 instead of Li.

[red31]

For me the purpose of a controller is to limit power going to a battery (trailer storage), that and 'sleep' or night mode were it prevents batt drainage. 'Full by noon' means the controller was limiting power before noon and the rest of the day unless you have some other use of the excess power.

In active use many things limit power, location, calendar, orientation, temperature, overcast, smog, shade, bird poop, dirt ...

[CA_Traveler]

naturist wrote:
Detail. Solar panels in series would charge longer during the day. That’s the good news. The bad news is that any part of any panel that is shaded will reduce the output of the whole array. When I bought my panels, I bought 12 volt panels, and because I have shading issues all the time here on the highly treed east coast, I’ve chosen to put half the panels in each of two series and then parallel the two halves. This to try and get the maximum output no matter what.

Basically incorrect due to bypass diodes. Serial panels have better output than parallel panels with regard to shadows. Your 12V panels may not have bypass diodes.

This shows the effect of 3 bypass diodes per panel and shade on 2 panel sections. Power is reduced by 2/9 vs parallel of 2/3. There is a small (about 0.3V) voltage drop for the conducting diodes.

[naturist]

Detail. Solar panels in series would charge longer during the day. That’s the good news. The bad news is that any part of any panel that is shaded will reduce the output of the whole array. When I bought my panels, I bought 12 volt panels, and because I have shading issues all the time here on the highly treed east coast, I’ve chosen to put half the panels in each of two series and then parallel the two halves. This to try and get the maximum output no matter what. The controller can handle up to 150 volts input from the array, no need to buy 12 volt panels, so if I were doing it again, I’d buy 24 volt panels, but I’d still do the paralleled pair of series panels.

If I were in the part of the country where shady campsites were the exception, I’d go series all the way. And here’s the beauty of those MC4 connectors: if you pay attention to connector placement during installation, it is simple to switch between parallel and series to change configuration for the conditions at hand.

[obiwancanoli]

3 tons wrote:
Regardless of their source - the basics are that photons can excite electrons from the phosphorus doped side of a PV diode to jump the barrier gate to get to the boron doped side...e.g. my 440w panels begin to harvest at sunrise and 200a Li battery charging (beginning at about 60% SOC) is often complete before or shortly after noon time, this mostly due to the high receptivity rate of Li..

3 tons

Precisely why I opted for Lithium batteries, to be installed next week, following the installs of the MPPT and V-meter

[3_tons]

Regardless of their source - the basics are that photons can excite electrons from the phosphorus doped side of a PV diode to jump the barrier gate to get to the boron doped side...e.g. my 440w panels begin to harvest at sunrise and 200a Li battery charging (beginning at about 60% SOC) is often complete before or shortly after noon time, this mostly due to the high receptivity rate of Li..

3 tons

[CA_Traveler]

Panels start producing voltage at very early morning light, however the amps are low. Maximum power occurs at noonish and their is significant power for several hours on either side. The power produced looks like a bell curve.

Other power factors include weather, panel orientation, time of day, time of year, shadows and temperature.

As a ball park figure I use 67% of the panel watts for 4-5 hours.

[dedmiston]

bgum wrote:
Issue: can an artificial light cause a solar panel to create a charge? Yes

It's strange to recall this now, but back when I used to travel daily to this thing called an "office", I'd see something in the men's room that always cracked me up: The soap dispenser and the automatic water valve (turned on and off by a beam that detected your hands) were both solar powered. The lights in the bathroom fed the little panels in the soap dispenser and water fixture.

It was one of those things that I had to force myself to not think too hard about, because I didn't want to blow a fuse.

[phemens]

Sure. Is it effective, no, but you get something off the panels. Good choice on the Victron MPPT and monitor. I would encourage you to get the version that has Bluetooth, their app is very handy for monitoring.

[bgum]

Issue: can an artificial light cause a solar panel to create a charge? Yes