Eletrical Gremlin on my bike

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Electrical Gremlin - I have gone round and round with my battery going dead on my 99 honda shadow ace tourer. I have replaced it with a new battery and have put it on a battery tender which i bought new also.. Light will go from red to green after a few hours so I believe that it is charging it..If you take it off and try to start it and it just clicks and not enough to start the bike. The bike has sat on the tender for about 3 weeks..

Something to add to the mix..I am running power to garage on 15 gauge extention cord and then put on a 6 outlet power strip which had a ground fault light which is lit.
older house with only 2 prong outlets in the house..
If I put the battery on a jump box charger it will charge it up also or if jump it with my truck it will start.
where should I start????:confused: