Thats normal...many recommend removing the cell covers while charging. Bubbles usually mean your battery was desperately in need of a charge. The bubbles will slow down as the battery charges. I't releasing gas. Don't light a match near the battery.
Tracy Blackford: Anaheim Hills, Ca www.pacificthunderperformance.com
65 Mustang, 331 custom built with 289 H beam rods and 383W piston, 282S cam, self-ported '70 351w heads, T5z, 9" w/3.50s. 430 HP@6500
Could be true that its normal to bubble. But, back in the days when I was a gas station grease monkey employee, a battery that bubbled acid during a charge was usually fried and wouldn't hold a charge for very long before it came back to us again.
\'67 Mustang fastback w/ 5.0efi & T5z; TCP suspension, steering & frame connectors.
2000 Explorer Sport 4x4