This wandboard Quad (32bit ARM) based microserver is solar powered thru a PV panel on my roof. There is a backup power source in case the lead-acid batteries get drained. This is controlled thru an Arduino that measures the battery voltage. It is connected to the Wandboard thru a serial connection to facilitate logging, shown in these plots:

Voltage plot last 72 hours (one averaged sample every 5 mins)

Voltage Plot last 7 days (one averaged sample every 30 mins)

The above plots are automatically generated every 15 minutes with python and matplotlib. The voltage is averaged over 60 seconds and logged once per minute. The daily plot (left) plots a point every 5 minutes (average of last 5 measurements) and for the weekly plot a point is drawn every 30 minutes (average of last 30 measurements).

system setup change log:
-- 23Nov2013: Wandboard microserver webserving up
-- 27Sep2014: Switched to solar power source (two 20W panels with 2x 9Ah Gel lead-acid batteries)
-- 23Aug2015: gel battery replaced with 55AH car starter battery (AGM)
-- 12Apr2017: Panel moved to roof (avoid tree shadow), fixed at 45 degree angle pointing south
-- 13Apr2017: entire system (wandquad + SSD + Arduino controller + Solar charger/battery) moved to basement
-- 23Sep2017: added 5 year old 90Ah car battery (estimated 60Ah capacity left)
-- 01May2019: removed old 90Ah car battery (draining energy)
-- 01Nov2019: replaced PWM controller with Victron Energy SmartSolar MPPT 75/10
-- 02Nov2019: added new 44Ah car starter battery (AGM)
-- 10Nov2019: replaced Arduino Voltage logger with a new one (charger-->mains; use other serial port to Wandboard)
-- 24Nov2019: replaced old 2x20W panel with new 100W panel, angled at 30 degrees, pointing south

Voltmeter and old Solar controller

Solar Trend controller - art.Nr. 03155 from www.sued-solar.de (website defunct) 12Vdc, power consumption: 4mA 120mm x 80mm x 25mm overload protection: 13.8 - 14.4V max load: 10A discharge protection: 11.1V Temp sensor for battery temp compensation

New solar controller (Nov 2019)

Example plots: 25 April 2017 / 5 Sept 2015 Day plot: red=some clouds - green=all day blue sky - blue=all day rain Week plot:2 Sunny days followed by 4 days of rain

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--Apache/2.4.51 (Fedora) OpenSSL/1.1.1l on Ronald's Wandboard Quad, last page update 10 Nov 2019 @ 12:03