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Solar panel shading

Itinerant1
Explorer
Explorer
With 1,280 watts of solar I don't worry to much about getting enough solar. This time of the year with the days getting shorter and we're in the national forest boondocking catching light shadows from some pines I would expect some drop off in amps going to the battery (can see it on the display).
Yesterday morning while I was walking the dog I was checking the shadowing on the panels from the trees from the hill behind the 5th wheel and noticed that the crank up antenna was casting a good shadow on 2 panels (each in a different series string). This morning at 10am I remebered about the antenna shadow and before cranking it down there was 25-26amp reading, after lowering it down 36-37amp. That's a pretty fair boost just lowering the antenna, during the day seeing we're not watching it anyways. I'll have to pay attention to the tv antenna during the winter so not I'm losing any possible power.;) We know about shadowing on the panels but seeing it yourself is a little eye opener.
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.
35 REPLIES 35

Itinerant1
Explorer
Explorer
"Adverse conditions" protocol condition to protect the batteries.
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.

Almot
Explorer III
Explorer III
BMS does control shutdown. This is its main purpose (besides cell balancing). It stops charging when charging voltage is too high, too low, or temperature is too high. BMS can not be (usually) programmed, but controller can be, yes.

Itinerant1
Explorer
Explorer
Without a doubt. Yesterday I tested it again by cranking it up and lowering to see the difference and it was the same as the first day. Amps would would lower and rise by just the antenna shadow.
Normal I don't worry about the positioning of the trailer but will think about the antenna now.
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.

CA_Traveler
Explorer III
Explorer III
Do you now feel that the antenna shadow was the main reason for the reduced charging for the given light conditions?
2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob

Itinerant1
Explorer
Explorer
Almot wrote:
Itinerant1 wrote:
These are lithium batteries no absorb.

Alright, then you donโ€™t need to push it to 95%. They are happier when staying in 20-80% range.
There is no Absorb or Float in Li battery, but the Float on the controller should be set low enough for BMS to stop charging (in absence of loads). I doubt that your battery BMS will automatically do this at 85%, so you'll have to do it yourself.

RV.net server is finicky today. No service, and then suddenly double and triple post.


Correct the batteries don't need to be in the 95%+ range which after overcast/ snow or just poor solar days and knowing that the weather will be better for replenishing the batteries. The system was installed so I could go 3 days with full convenience without having to hook up the generator for a hold over charge till the sun shines again. The lowest the batteries have been down in the morning while still using the microwave or coffee maker is 24% (120ah).
I know how my setup works after 18 months which is why I was wondering why it wasn't recovering as normal and something so simple as the tv antenna that I never thought about or at least had an impact is it did at this location and time of year.
Without going in to detail with these fully programmable inverter/ charges working in unison of the solar controller the bms is not controlling shut down other than programed
adverse condtions.
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.

Almot
Explorer III
Explorer III
dp

Almot
Explorer III
Explorer III
dp

Almot
Explorer III
Explorer III
Itinerant1 wrote:
These are lithium batteries no absorb.

Alright, then you donโ€™t need to push it to 95%. They are happier when staying in 20-80% range.
There is no Absorb or Float in Li battery, but the Float on the controller should be set low enough for BMS to stop charging (in absence of loads). I doubt that your battery BMS will automatically do this at 85%, so you'll have to do it yourself.

RV.net server is finicky today. No service, and then suddenly double and triple post.

BFL13
Explorer II
Explorer II
liborko wrote:
Good catch time2roll. I realized that as soon as I posted it.


You are allowed to edit your posts, you know. ๐Ÿ˜ž
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.

liborko
Explorer
Explorer
Good catch time2roll. I realized that as soon as I posted it.

CA_Traveler
Explorer III
Explorer III
liborko,

The example I posted was 7 current sources and 2 bypass diodes in series for the 9 sub panels and the output was not 0W. Plus the link I posted clearly shows how bypass diodes work, and the output was not 0W for the graph.

Google bypass diodes for solar panels and you'll find various articles and explanations that may help you to understand.

time2roll has it correct. I deliberately did not introduce the small diode voltage drop to keep the example simpler.
2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob

time2roll
Explorer II
Explorer II
liborko wrote:
Output from panels in series with one panel in shade:
8A*30V+8A*30V+0A*0V=0W !!!

Your analysis would work if there were 9 resistors in series.
Actually there are 9 bypass diodes (not resistors) in series.

(30V + 30V -1.5V) x 8A =468W would be closer to the equation.

Also note empirical data in the OP. (hint: answer is not zero)

liborko
Explorer
Explorer
CA Traveler:

The math in your example is incorrect:
Theoretical output of panels in series hook-up with no shade
8A*(30V+30V+30V)=720W

Theoretical output of panels in parallel hook-up with no shade:
(8A+8A+8A)*30V=720W

Output from panels in series with one panel in shade:
8A*30V+8A*30V-8A*1.8V=465.6W

Output from panels in parallel with one panel in shade:
8A*30V+8A*30V+0A*0V=480W

Your analysis would work if there were 9 resistors in series. Instead there are 9 CURRENT sources in series. Not the same thing.

Assuming partial shade of one panel,the output would be:
Panels in series-anyone's guess
Panels in parallel-at least 480 watts

Itinerant1
Explorer
Explorer
Almot wrote:
Itinerant1 wrote:
... battery bank normally gets back to 95-100% even after a couple/ few days of playing catch up but in this location it's been getting to 70% (350ah) by sundown ...
That's what seemed odd to me that I wasn't gaining back the lost power after a couple days of heavy overcast and snow. The way I'm parked and the path of the sun is enough for the antenna shadow to stay on the panels a fair amount of the day.

Hard to tell why it couldn't catch up to 95% when changing the location. Antenna shade could've contributed, or this location had some trees/mountains blocking the early sun when you needed it the most, or there is less sun in late October than it was in August :). Or you changed the time pattern of loads. Increased current is needed only until you get to Absorb, then you can get by with very little charging current - until you turn some heavy loads on. If battery can't catch up past 70% - change the way you run loads, avoid running heavy loads after sunset.

Most solar systems require a fair amount of self-discipline, charging all the tools and running other loads is better in daytime - especially after the battery went to Float. Then you could use the energy from the sun directly, rather then discharging the battery. Battery stays in Float, sun runs your devices.


These are lithium batteries no absorb.

Beleive it or not the antenna shadow was enough to drag the power from the 2 series strings. Same weather conditions as the past few days and between yesterday and today the batteries are just about full again.

Thanks again guys.
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.