Welcome to the forum Passonofaz,
I would ask you to open a discussion (new thread) for your questions/discussions about your system (create just one discussion about your system--Keeps all the Q&A about your system in one place--Less confusion). We are not really setup for "wall" discussions.
However, to answer your question, the best harvest I would expect (cool/clear day, spring or summer, near solar noon, with a discharged battery bank) is:
- 500 Watts * 0.77 solar panel+controller deratings * 1/14.5 volts charging = 26.6 Amps "best case" typical (few days a year, for maybe an hour on random days)
And depending on actual weather, how clear the sky is, etc... seeing anywhere from 50% to 100% of 26.6 Amps can be perfectly normal (haze, moisture, dust, smoke, dirty panels, etc. all affect harvest).
The things to look at/understand. For an off grid power system, the actual charging current depends on the batteries (batteries >~80-90% State of Charge) naturally reduce the charging current (from roughly 10% of bank capacity, to under 1% when fully charged). That may limit the peak charging current you see.
And other major question--The charge controller also controls the "average" battery charging voltage. For a Flooded Cell Lead Acid battery, nominally 14.75 volts for a battery bank @ 75F (actual charging voltage set point depends on battery/ambient temperatures too--Cold batteries need higher charging voltage).
Also, the charge controller has three different charging modes (typically):
- Bulk: Charge controller is outputting maximum available solar current from array. And battery voltage is below Absorb Set Point (below ~14.75 for FLA batteries)
- Absorb: Once charge controller reaches set point voltage (14.75 VDC for FLA), charger will hold that voltage and the battery bank will naturally limit actual charging voltage. Absorb voltage is generally held for 2-6 hours (shallow discharge, closer to 2 hours. Deeper discharge closer to 6 hours).
- Float: Once the battery bank has gone through "bulk and absorb" state... The charge controller will cut back to float voltage set point--Typically around 13.4 to 13.6 volts or so (FLA).
There can be other issues limiting charging current. Damaged/failed solar panels. Shading on one or more cells on a panel (shading kills output current from panel/array). Poor/bad electrical connections (in array, around controller, battery bank). Too small/too long of cables from charge controller to battery bank can do this too.
Or, you may simply not discharging the battery bank very much (have to discharge below ~80% or more to "see" max charging current) and/or have other heavy DC loads (AC inverter running a heater, etc.).
If you have a combiner box with circuit breakers--You can turn off one panel at a time and see if you lose 1/5th of the charging current or not.
You can also get an AC+DC Current Clamp DMM and measure the current for each panel/string and make sure they are sharing:
https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (inexpensive DC current clamp meter)
https://www.amazon.com/gp/product/B019CY4FB4 (mid-priced DC current clamp meter)
Note there are also AC only Current Clamp meters... They work well for AC voltages/current... But do not work on Battery/DC power systems.
Having a hydrometer and an AC+DC current clamp DMM are some very nice tools to have for off grid power systems (and for car/boat electrical systems).
https://www.solar-electric.com/search/?q=hydrometerTake care,
-Bill
July 28
HandymanJoe,
I have my solar array wired and operating. The readout on my CC says 14.7 volts going to the batteries. Now when I turn on the inverter i only get 108 volts from the 110 socket. Have i made a mistake along the line from the panels to the inverter? After spending all this money i don't have a voltage that will run my Dremel. What next? need all the help i can get at this point.0 ·July 27
