Originally Posted by Seahunter
Even at 10 watts output without a controller a solar panel nearly .75 amp per hour (over 18 Ahrs per day) will be produced. This is enough to boil a wet cell away in a matter of days. As well a calculation based on 13.2 VDC (closer to a real voltage) and 10W produces nearly .76 Amp not .6 Amp.
Seahunter I do not want to get involved in any of the long winded negative threads that can sometimes occur in this type of forum, but to help everyone’s understanding have a look at your battery monitor
when your solar controller has fully charged the batteries and is in float mode. (or measure the battery input with a multimeter)
What is the reading?
Unless your battery bank is small I guarantee it will be over the 0.76A you are concerned about.
( Incidentally a 10w solar panel will not produce 0.76A without a MPPT
controller Solar panel output is rated at Vpm or voltage at load. This is typically about 17-18v. Unfortunately solar panels
will not produce much more current at the more typical battery voltages. This is a characteristic of all solar panels
and is the principal that MPPT
extract slightly more current from solar panels
If we take the common Kyocera
10w panel it will produce under ideal conditions 10w at 17.9V or 0.56A . Unfortunately at the 13.2 V you quoted it will still produce the almost the same current.
Without a controller (so no MPPT effect) 0.6A from a 10w panel would be an very good result. In practice only seen, briefly, when the sun was very strong, in cold conditions, when the panel was angled perfectly, and sun emerged behind a cloud. The combination of direct sunlight as well as light diffused from the nearby clouds can raise the irradiance above the rated 1000w/square meter.
Without a MPPT controller the 0.76 A you expect from Ohms law will never be seen, even briefly under the best conditions.
The 0.6A I used for a 10w panel, directly connected to the battery, is accurate, or optimistic )
!8Ahrs from a 10w panel is also much too high. I am crusing in Greece
at the moment, with a very high insolation value in summer. My 330w panels would produce 33X18 = 594 AHrs based on your calculations.
I wish this was the case, but 150-175 Ahrs is a good result on a summers day.