You can use an automotive charger to charge the gell cell batteries mentioned above. The downside is that they are timed chargers typically, and don't necessarily charge it to its fullest. I would say pick up an MRC Super Brain 977 (or two) and you can PEAK charge starter box 12 volt batteries. It also charges two different batteries at once, so you can spend more time driving and less time charging batteries.

I use a power panel on my starter box, so that way that giant 12 volt gell cell battery can power my glow ignitor too. That way I can go days at a time without worrying about charging stupid glow ignitor batteries.

Between my Super Brain charging my radio batteries and my starter box (simultaneously), and my Duratrax Pirhana Digital charging my car battery pack, I can charge them all at once. The car and radio typically take about 30 minutes to charge, the starter box (depending on how dead it is) is between 1-5 hours. So I either set them up to charge the night before, or the morning of.