A maintainer will never fully charge a pair of GC-2's. Period.
They are designed and intended to maintain a fully charged battery, at full charge.
0.5 amps is never going to cut it as a charger on a battery larger than 20Ah capacity, even if it will output that much amperage until battery voltage climbs to 14.4v.
You are destroying your new batteries.
A hydrometer will open your eyes. So many people have ridiculous faith in their product's marketing, when a hydrometer will prove that their whizzbang charger is incapable of doing anything that its marketers claim it can.
'But the green light was on!!!!!"
SMACK!
