''If I have a torch and I am out at night relying on the torch to find my way home and my battery fails then I would find it unreliable.''
then, you have brought the wrong torch and certainly the wrong battery
wake the hell up - solar panels don't fail - nor do wind turbines. When the odd one does - there is a huge redundancy (eg. we had a turbine fire in Oz last week - 1 turbine rendered useless - on the same day 2,999 worked perfectly and continue to do so)
your walking home at night problem with a 'failed battery' ---------- means that YOU haven't done your job
you have probably brought cheap crap - AND you do NOT have a redundancy -
a little led keyring, an iphone as redundancy - job done --------- you had a system with zero redundance AND you've purchased crap equipment
you have failed because your system is too simple, badly engineered, no redundancy and poor purchase choices
it is YOU that is unreliable ------- incapable of imagination, vision and basic engineering and planning
