I had a solar one where i would have to charge battery every month from new. Thought it was a heap of crap. Did put out 8000v fully charged and you could hear the crack when something touched it from 100 meters away. After 10 years the battery was well and truly dead and i always believed the battery was at fault. New battery and still needed monthly charge. So one day i tore it to pieces and did some testing. Turns out some drongo hooked the solar panel up the wrong polarity. Regulator was toast but panel still putting out 18v. I wired in a new cheap regulator and bob's your uncle, been working non stop just from solar charge for 18 months now.