More Solar for "Us"

[MrWizard]

Ok, I went off.the deep end?
Bought 3 used 37watt uni-solar panels and a blue sky 2000e controller for the hefty price of $400,
They were being listed as 75w panels, they are not

The tested open circuit voltage was 21+, short circuit amps 2.9
I tested each panel multiple times tilted into the sun and laying flat on the ground , got the same readings each way, that was the deciding factor, they appear to put out full power while laying flat, I will try to mount them tomorrow before it gets hot, right now 104°F
I will use the existing wiring until I buy & install the new wire

[JimK-NY]

I just found this thread and scanned through all 18 pages. Trying to get the best performance from solar panels seems to be only half the battle. Equally important is to conserve power use.

On the production side, I upgraded my batteries to 2 x 150 AH, size 30 Lifeline AGMs. I added a second 135 watt Kyocera panel.

Equally important, I decreased my power consumption. My wife got an efficient 12v CPAP which should pull about 20 AH/day instead of the previous 40+ draw. I replaced all my tungsten bulbs with LED bulbs. I even replaced my 2 fluorescent fixures with LED fixtures. Now I pull about 1 amp to light the camper with several lights on instead of over an amp for a single bulb. The biggest change I made was to replace the fridge. Instead of drawing 80 AH or much, much more in hot weather, I will now use about 20 AH/day for my super insulated Nova Kool r4500. I did give up some fridge/freezer capacity but that beats dealing with a genset for hours a day. In the winter, solar will be tough but when we get into the summer months the solar should surpass my consumption with even a few hours of daily sunshine. I have checked my solar production several times on sunny days. The results are always close to the theoretical production: http://www.where-rv-now.com/Notes/Solar/index.php#Calculator

[MrWizard]

three weeks until winter solstice

todays solar.charge readings are
769.30 watt hrs
56.92 amp hrs
152.7 peak watts
11.41 peak amps

[MrWizard]

mounting feet came on my first set of panels , and I made the feet for the second set
our panels are an inch or more of space from the roof

[Salvo]

Yes, heat is a big issue with solar panels. For best performance, you want to keep the panel as cool as possible. A air gap between roof and bottom of panel is a requirement for a good design. I've seen new frame designs that have vertical holes at the sides of the frame to prevent the hot air from getting trapped. Performance with a standard PWM controller isn't affected nearly as much as MPPT.

Besides reduced performance, heat kills. I'm sure a hot panel will not last as long as a cooler one.

I didn't have any vibrations concerns for my 130W Kyrocera panel. However I didn't think the frame was stiff enough. Especially when it's tilted towards the sun. I significantly stiffened the frame with angle Al.

Sal

[pianotuna]

Hi,

On my curved roof I mounted the panels as close to it as possible. I wished to keep wind loading to a minimum. Providing for cool air flow is a nice idea but probably on an RV a bit down the list. Keeping the panels out of any shade from other things on the roof is far more significant. So is using large fat wire.

I'd be more concerned with a glass panel flexing if flexible mounting for anti-shock was used. My panels have no glass so it is not a concern--but I still mounted them in a manner that should prevent flexing. (i.e. angle aluminum along the long sides of the panels.)

[2inAlabama]

When mounting a solar panel on top of a RV, shouldn't it be mounted so that air can get under it? Not trying to criticize anyone, but I have seen some members here who have mounted their panel almost flush against the surface of the roof. Isn't it true that heat buildup in the panel will affect the efficiency of the system?

Another question. Are solar panels affected by vibrations? Is there a need for shock mounts to mitigate this effect?

Just wondering and trying to learn how solar works and how to install one.

[Bill__KE7FSV]

After several months of waiting, my 135 watt solar panel arrived.
Of course, the weather has gone south so it will be a spring time install now.
About ready to order another one.

[MrWizard]

10.2 amps.from panels

10.59 amps to the.system

3.8% mppt increase

clear sunny and very windy

days like today , I make sure I'm in the clear and up wind of the trees, no shade today

[MrWizard]

permanent one has not been ordered yet,
friday night I installed a Harbor Freight special (1200w-3200surge)

sat & sun we have been doing support "hand holding" "compassion duty" one of our friends had a heart attack 4:30 am Sat morning and we have been parked near the hospital since Sat night,
she had two blocked valves, but is now on her way to recovery

I'm going to try and make a decision and get the replacement ordered

so far the Hf model is working great, its a no frills model no remote no display no pass thru, but its in an outside compartment with the wfco and the transfer switch, so its easy access and I don't need to turn it off, it stays on 24/7 so the fridge and residential lights have power

[mena661]

MrWizard wrote:
no data. meter reset disconnected batteries while removing failed Freedom-10 inverter-charger

What inverter did you decide to get?

[MrWizard]

some numbers on daily performance

Thurs 10/28
Watt hours 1026.3
Amp hours 72.94
Peak amps 13.44

Fri 10/29
no data. meter reset disconnected batteries while removing failed Freedom-10 inverter-charger

Sat 10/30
cloudy morning,.sunnyafternoon
watthrs 693.3
Amphrs 49.83
Peakamps 14.61

Sunday 10/31 mostly sunny
watt hrs 982.4
amphrs 71.05
peak amps 13.52

[Salvo]

Hey Jim,

Glad we're in agreement. But I certainly don't want to get dragged into a my solar controller is better than yours debate. 😉

Not dropping the setpoint voltage is definitely a Blue Sky weakness. My old G24 batteries used about a quart of water a year. And that's with the setpoint at 14.0V! More than 99% of my charging is done solely with solar. BTW, welcome to the solar club. You will be happy with it.

I don't understand Wiz last measurements.
Controller 14.64V
Battery 13.81V
Current 10.1A

That would indicate a line resistance of 0.83V/10.1A = 82 mohm

Previously I calculated 11 mohm.

Something is not right.

Sal

[bigfootford]

Salvo wrote:
Setpoint has everything to do with the MPPT efficiency. First off, the controller doesn't know the voltage of the battery. It calculates the most efficient power point by using the voltage at the output of the controller, not battery voltage. There is no battery sense line.

Of course there is no "sense line" but the controller has the charge wires attached to it that are basically sense wires because the controller will react to a load/ low battery.

Blue Sky Energy - Solar Boost 2000E

Because output power is constant while MPPT is operating, anything that leads to lower battery voltage will produce an increase in Output Charge Current. While a discharged battery is one way to produce lower output voltage, and therefore higher output current, other normal conditions may produce lower voltage as well. Any 12 volt power consumption during the day will decrease net battery charge current, which decreases battery voltage.

There are a few bad things happening with a high setpoint.

1. The higher the setpoint, the smaller the difference between controller input and output voltage. You've now eliminated the advantage of MPPT. MPPT wants to see a large voltage difference between input and output.

There are two adjustments on the 2000i. One for Mppt and the other is for Setpoint. I have played with these settings.

Some controllers do the matching without performing a panel match adjustment.

From the Bluesky 2000I manual:

OPTIMIZING MPPT 2000I:

The maximum power voltage setting (VOC - VMP) is a nominal value. The combined effects of manufacturing tolerances in the PV panel and wiring resistance in a particular installation can sometimes shift the optimum setting.
While not required, it is recommended that for maximum boost performance this adjustment be fine tuned following
installation. Fine tuning is also desirable following installation of additional PV panels.
Fine tuning is easily accomplished by slowly adjusting the MPPT adjust potentiometer to obtain maximum
Output Charge Current. Adjustment is best done in full sun with a discharged battery and cool ambient
temperatures. Verify that a slight drop in output current is seen on either side of the peak. If a drop on either side of
the peak is not seen, MPPT is not fully operational due to a combination of high PV temperature and/or high battery
voltage. MPPT can usually be made to operate by lowering battery voltage through application of a heavy DC load.
If in doubt, leave the adjustment at the factory setting position as shown in Figure 3.

2. The higher the converter output voltage the lower the charging current.



3. Gassing increases. Battery overcharging.




BTW Jim, you better read the Blue Sky manual before giving false information.
Have read and performed the adjustments...I had the Morningstar Sunsaver in my mind.

Sal

bigfootford wrote:
Mppt is a function/feature that a controller does and has nothing to do with the setpoint.

The BlueSky 2000e can reach setpoint in either Mppt mode or PWM...
Jim

If a controller has the setpoint feature then when the setpoint voltage is met which is the output of the controller to the battery then the controller will revert to the absorb voltage which is lower than setpoint. The Absorb voltage is usually low enough to stop gassing.

I stand corrected...Several other Mppt controllers do drop to a lower absorb voltage but the 2000i does not.

This is just one of the reasons I ended up with the Morningstar sunsaver.

Jim


Jim

[MrWizard]

9AM

Panel Amps 5.5
Output Amps 5.9, PowerMeter says 5.93 amps
Voltage 13.12

Mppt is working, is it at max conversion ? IDK
But doubling the numbers to 11 & 11.8 follows the "conversion efficiency" in Salvos post ( 10.0 & 10.7 )

10:30am
generator is on, converter is charging at 15.1 amps
solar input 5.8a BS output 7.0 amps voltage 14.64

total amps charge 22.1, voltstage at batteries 14.14 ,
just the slightest of bubbles now & then ( 20>30 seconds )

yeah we have out gassing 😉

getting my.morning bulk charge , so I can let the solar do the top off and hold the batteries up while powering the fridge during the day

I will keep a watch on the batteries

11:45am

generator OFF, NO CONVERTER charge , Solar only

panel amps 9.3
output amps 10.1
controller volts 14.64
voltage at batteries 13.81 no gassing observed

[vcallaway]

I'm not a fan of the bluesky controllers. The charging modes leave a bit to be desired.

The charger does need to have a point where it desulphates the batteries. Too low of a voltage will shorten the life just as much as too long at boil point. Those voltages are usually specified by the battery vendor.

One reason Trojan batteries are so popular is they provide all the details needed to tune your charger. Trojan Users Guide.

Following their charge and equalization guidlines will greatly increase the life of your batteries.