Solar Panel Tilt Adjustment


Solar Panels

Time for a seasonal adjustment of the tilt on the solar panels.   Today they were re-tilted to 17 degrees instead of the 40 they had been set to which is shown in this picture.   They will be changed for winter/summer.  This new tilt was obtained from one of the many online calculators.  Next step is to see what time battery “float” condition is reached each day.  It had previously been 1 pm.  With the new tilt float still comes after noon so more panels are probably needed.  On Summer Solstice, June 21, 2018 at 1:00p Mountain Daylight Time, the sun peaked at 17 degrees as measured with an angle detector.  The 17 degrees calculation seems to be ideal for Denver summer’s insolation.





  1. exposure to the sun’s rays.
    • the amount of solar radiation reaching a given area.

Update: Additional solar panels were added so the batteries can reach float more dependably especially in the winter.  These also can be tilted to match the prescribed angle for the season (shown at their old summer setting).  The new panels have their own controller which is connected in parallel with the original controller at the battery terminals.  A parallel connection works because each controller monitors the battery voltage and applies charge as needed. They do not fight each other or require any synchronization.


One thing leads to another.  Upon attempting to connect the new panels it was discovered that there are no more vacant power jacks on the battery bank RigRunner panel.  John, KC0RF,  a telecommunications power engineer, observed we needed some serious reworking of the battery wiring to stay safe.   John insisted on having separate buses created for the charging and for the distribution, and fusing the charge connections to the battery.  Here is a white-board sketch that shows how the recommendations were implemented.


Ground wires are left out of the drawing but each battery string also has a (negative) ground wire that is home run to the buses along with the positive leads.   “Essentials” in the sketch above are the router, Ethernet switch, and internet modem.  They are not switched by the RigRunner 4005i like everything else.  “Controller” is the solar controller for the two panel arrays.  The small rectangles represent 30 Amp inline fuses.  The “Charge Bus” is along the top and the lower bus (not labelled) is the “Distribution Bus”.  All wires are 10 AWG.

It looks like a mess but John said it was pretty, knowing the installation was now safe and up to telecommunications standards except for cable dressing. Pictured are 8 golf cart batteries which are 6 volts each, wired according to the diagram above.


Now there is a location to connect the new solar controller and yes, the batteries reach float earlier in the day.  But that’s all changed.  See “From Lead Acid to Lithium”

September update:  The panels were tilted down to 26 degrees for the winter.  Unfortunately there wasn’t enough room between the bottom of the new panels and the ground to allow for snow.  A cedar post was installed and the panels were moved up.  Plenty of room for snow now, just in time because it was already snowing today.

IMG_0016 (1)

Update:  The tilt on these panels looks too steep.  The sun doesn’t peak at that low of angle above the horizon on December 21 in Colorado.  Consulting solar web sites we determined the ideal angle for this latitude is 26 degrees for winter.  The tilt was readjusted and float is being reached much earlier in the day ever since.  Where did those old angles come from, anyway?

Update:  The 26 degree angle and the second panel has worked perfectly over the winter.  On December 21 (worst case because it’s the solstice) the batteries reached float by 11am.

Another Update (summer 2019):  The two solar controllers connected in parallel have been replaced by one controller with large capacity.  Although two controllers did not fight each other they did give each other false readings.  If one controller was charging the battery the other controller saw that higher voltage and decided the battery was fully charged.  Vis-versa.  Even though they didn’t fight each other they did confuse each other.  Only one panel could be charging at one time.   This was effectively only a one panel system.  A new controller that can handle all the panels all the time will keep the batteries charged better it is hoped.

Spring 2020 update: Cells tied together as one big battery and both solar controllers paralled as before to make one system rather than two separate ones.  Eight CALB brand lithium 100AH cells were added over the winter and now all 16 cells are one big battery.

The controllers are behaving nicely.  In the morning when the battery is lowest and needs the most charge the controllers both deliver their current at the same time.  As the battery nears the top the controllers alternate.  One stays in the bulk state and the other goes to absorption.  After a few minutes they switch.  This seems to be keeping the battery charged as intended.

Solar tilt:  As an experiment the tilt of the panels has been left at 26 degrees for the summer.  The thinking is the panels will be able to produce enough power even at these angles and it will save a lot of work every spring and fall.  At the end of April it is working and the summer should only get better as the sun angle gets higher.


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