vinke said:
I am perplexed because while on load the battery voltage may drop much below its actual voltage.
Thanks
your batterys are to small in capacity or they are old and almost gone
the baterys you need is deep cycle ones
as sugested earlyer marine batterys will do electrical wheel chair batterys are also good
the size you should have is depending what you do
you mentiont 5 amps for 1/2 hour maximum on a day
take that tripple (safety factor of 3) = 7.5A/h
Cable losses,
Tempature differances from your battery will effect greatly the capacity (best tempature is about 20 to 21 Degree Celcius)
assuming that you have at least sunlight for 6 hours
and on a cloudy day still be able to get 40% of the capacity from your pannels
7.5A * 12V = 90
90W : 6hours = 15 W/h
15W * (100 : 40) = 37.5W that should be your capacity of your panel
this only a guid line and you will be able to tweaq this system furter
there are many factors still not compute in this but this gives you at least a workable set up
solar panels tend to be more efficient in colder climates
tempature of the battery is a big factor
i also atache a schematic of a solar (dis)charge controler
i did build this one my self and it works fine
there is a battery low voltage protection in it a short circuit protection and a charge controler incorparated in this circuit
Sucsess
Robert-Jan