Solar CHrger for Ring2

I just reciently bought a new Ring 2 with a solar charger. So far I have had to charge the battery twice as the charger doesn't seem to charge it. I double checked to see if I had it installed correctly and that is not the problem. Now the battery is back down to 13%. The Ring is on a southen exposure with direct sunlight. My other ring2 with a solar charger works great and it has the same exposure. I even bought another battery because of the charging problem. It seems like the battery doesn't last very long.