Reproduction battery dilemma

[davepl]

I'm running two reproduction batteries in my truck, both are gel reproductions from RestorationBattery.com which is now long gone, unfortunately. One is a reproduction of the bigger T-60 and one the R59. That's what I found you should have if you have both the dual and the HD battery options (which only gets you the one HD battery and one regular, not two HD).

Anyhow, it was on a C-TEK charger a week ago and I came into the garage in the morning to a strong "hydrogen something or other" smell. Not quite rotten eggs but quite distinctive as the smell of overcharging.

Now I notice the battery has a crack in the top of it! And this is a sealed battery.

So something went wrong but now what? Is it the charger or the battery, and how do I deduce that without burning down my garage as a step?