Although SLA batteries are quite robust, they are not car size batteries. The max safe charge rate for any lead acid is the 10 hour rate, this is a great many more amps for a car battery than one of ours, and that is the rate that a car charger will try to shove in. A car battery, with a liquid electrolyte, can often be topped up if any is bubbled off because of excess charging. A sealed gel cell does not allow for this, being a) sealed and b) gel.
The right charger is usually cheaper than the replacement battery.