Picture of Solar PV charge/discharge current monitoring
NOTE ( Feb. 2013) : This Instructable is now dated, but has been retained for convenience. Some approaches considered here are now  poor practise. Refer instead to a fresh Instructable => 

"Backyard" photovoltaic solar setups increasingly abound, but they usually run "blind" with charging performance often unknown.  Simple LED indicators,although better than nothing (see perhaps ), may not be revealing enough for keen investigations. Full current flow monitoring (both INTO & OUT OF a solar setup), perhaps via a cheap (US$5-$10)  pocket style DMM (digital multimeter), can be near essential in many setups.

An ammeter can give valuable system insights!

Under  charge  it can reveal slight changes in panel performance due to air quality, cloud cover, aging, placement, inclination or seasons and also drop offs arising from such tedious issues as leaf/dirt/bird droppings or corroded & suspect connections.  Naturally panel damage (or even theft - it happens!) will be quickly spotted too. The relative merits of assorted batteries and panels that may become available can be  investigated as well.

Discharge  performance checks of new devices (or alerts to excessive or un-authorized loads) can be quickly noted, while longer term battery degradation can also be monitored.
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Step 1: RC Electronics WU100-BK "Watt's Up" Watt Meter

Picture of RC Electronics WU100-BK
OK -for serious monitoring work a Watt meter just HAS to be considered !  Perhaps the best known is RC Electronics ( => )  popular  "Watt's Up"  Watt meter, (~$US50 via Amazon/EBay etc), which is held in very high esteem. Although intended for  RC (Radio Control) enthusiasts, it's considered a valuable diagnostic & monitoring aid for all manner of  battery charge/discharge applications. Professionals should get one !

However this is an Instructable after all, so follow on for DIY approaches !



Cool! Next you could add an Arduino with a WiFi and hit the info from your phone. XD