Is it also possible that while rewiring your folding panel to a series connection you mixed up the and leads for the set.
My solar panel has voltage but low amps.
And running 50 feet one way run at 4 amps on 10 awg the voltage drop would be.
100 watts 17 5 volt vmp 5 7 amps imp.
The battery does not have the ability to power the light bulb but will show some voltage at no load.
It is the same thing as if you had a battery that shows voltage but when you hook it up to a light bulb the battery drops to zero volts.
Another reason is that the panel with 0 amps can t handle any load.
As the pv modules are connected in series one failing pv module will shut down the entire system.
Short the panel and measure your isc in noon time sun use a 10 amp dmm or use a dc current clamp type meter.
Some prefabricated interconnect cable sets are wired in a non standard way and matching colors of the mc4 connectors will cause the panel to be wired in backwards.
Solar panel produces volts but no amps.
Simply touch the solar panel leads with the multi meter probes matching their corresponding polarity red to red black to black.
Some exceptions may apply based on panel type.
If it is proceed.
Calculate the current in amps by dividing power in watts by the voltage in volts.
Zero output is a common problem and in nine out of ten cases it is due to a faulty inverter or charge controller.
For example if the solar panel is rated at 175 watts and the maximum power voltage vmp is given as 23 6 volts.
Measure the battery voltage.
Connect the ve solar controller output lead to the ve battery terminal.
Measure the solar panel controller output voltage try to get maximum voltage by angling the panels.
It may be that you can never get more than 12 13v.