1999 Chev Blazer alarm going off?

ok, you charged battery, as to say something was killing the battery (running it down) or batt not getting a good charge from alt. You changed batt and it was fine for a while.. so, using your key fob to lock doors, you could have an actuator sticking and pulling constant power. More likely some other system is drawing too much power or power when not supposed to. Remember you can lock doors using a key too (good old days).